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{{nota disambigua|l'omonima navetta cargo europea|[[ATV-002 Johannes Kepler]]}}

|- bgcolor="#003399"

{{Infobox missione spaziale

! style="color:white" colspan="3" align="center" | [[Classificazione dei pianeti extrasolari|<span style="color:white;">Classificazione dei pianeti extrasolari</span>]]

|nome_missione = Missione Kepler

|rowspan="7"|[[File:Hypothetical exoplanet.jpg|155px]]

|programma=Programma Discovery

|precedente= [[Missione Dawn|Dawn]]

|successivo = [[Gravity Recovery and Interior Laboratory|GRAIL]]

|foto_veicolo = Telescope-KeplerSpacecraft-20130103-717260main pia11824-full.jpg

|descrizione_foto_veicolo = Immagine d'artista del telescopio spaziale Kepler

|proponente = NASA

|aziende = [[Ball Aerospace & Technologies Corp.|Ball Aerospace]]

|NSSDC_ID = 2009-011A

|destinazione = [[Osservazione astronomica]]

|esito = in corso

|spacecraft_name = ''Kepler''

|booster = [[Delta II]] (7925-10L)

|luogo_lancio =[[Cape Canaveral Air Force Station]], PAD 17B

|lancio = [[7 marzo]] [[2009]]

|durata = ≥ 7,5 anni

|data_inserimento_orbitale =

|orbita = Eliocentrica

|periodo = 372,5 [[giorno|giorni]]

|eccentricità = 0,03188

|semiasse_maggiore = 1,01319 [[Unità astronomica|UA]]

|massa = 1039 kg

|strumentazione = Specchio principale con apertura di 0,95 m

|web = http://kepler.nasa.gov

}}

|- style="font-size:90%"

'''La missione ''Kepler''''' è una missione spaziale della [[NASA]] parte del [[programma Discovery]], il cui scopo è la ricerca e conferma di [[pianeta terrestre|pianeti simili alla Terra]] in orbita attorno a [[pianeta extrasolare|stelle diverse dal Sole]], tramite l'utlizzo del telescopio spaziale Kepler.<ref>{{cite web |last1=Koch |first1=David

| width="10%" |'''Massa'''

|last2=Gould |first2=Alan |title=Kepler Mission | url=http://www.kepler.arc.nasa.gov/ |publisher=[[NASA]] |date=March 2009 | accessdate=2009-03-14}}</ref> Il veicolo spaziale, chiamato in onore dell'astronomo tedesco del diciassettesimo secolo [[Johannes Kepler]],<ref>{{cite news |last=DeVore |first=Edna | title=Closing in on Extrasolar Earths | url=http://www.space.com/searchforlife/080619-seti-extrasolar-earths.html | work=[http://www.space.com/ SPACE.com] |date=9 June 2008 | accessdate=2009-03-14}}</ref> è stato lanciato con successo il 7 marzo 2009.<ref name="KeplerLaunch">{{cite web|author=NASA Staff |url=http://www.nasa.gov/mission_pages/kepler/launch/index.html |title=Kepler Launch |publisher=[[NASA]] |accessdate=2009-09-18}}</ref>

| colspan=2 width="90%" |[[Cometa extrasolare]] • [[Asteroide extrasolare]] • [[Pianeta mercuriano|Mercuriano]] • [[Pianeta subterrestre|Sub Terra]] • [[Pianeta di massa terrestre|Terra]] • [[Pianeta superterrestre|Super Terra]] • [[Mini Nettuno]] • [[Pianeta nettuniano|Nettuniano]] • [[Pianeta Gioviano|Gioviano]] • [[Pianeta supergioviano|Supergioviano]] • [[Sub-nana bruna]] • [[Nana bruna]]

|- style="font-size: 90%"

Il telescopio Kepler è stato "specificatamente progettato per monitare una porzione della nostra regione della [[Via Lattea]] e scoprire dozzine di pianeti simili alla Terra vicino o nella [[zona abitabile]], e determinare quante delle miliardi di stelle della nostra galassia posseggano pianeti".<ref>{{cite web |author=NASA Staff |title=Kepler Mission/QuickGuide |url=http://kepler.nasa.gov/Mission/QuickGuide/ |publisher=[[NASA]]|accessdate=2011-04-20}}</ref> Per fare ciò, un [[fotometro]] monitora costantemente la luminosità di più di 145.000 stelle di [[sequenza principale]] nel suo campo di vista fissato, presso le costellazioni del [[Cigno (costellazione)|Cigno]], della [[Lira (costellazione)|Lira]] e del [[Drago (costellazione)|Drago]].<ref>{{cite web |author=AAS Staff |title=Meeting Program and Block Schedule |url=http://aas.org/node/651 |publisher=[[American Astronomical Society]] |accessdate=2011-04-20}} – click the itinerary builder to get to the abstract of "Kepler Planet Detection Mission: Introduction and First Results".</ref>I dati sono trasmessi a Terra, dove vengono [[Metodo del transito|analizzati]] in cerca di periodiche diminuzioni di luminosità delle stelle causate da pianeti extrasolari che [[Transito (astronomia)|transitano]] di fronte alla loro stella. Nel marzo 2013 il team di Kepler aveva individuato 2.740 candidati pianeti e confermato [[Lista dei pianeti scoperti dalla missione Kepler|altri 115]].<ref>[http://www.ustream.tv/recorded/28311736 "Exoplanets Coming & Going Everywhere pt1"]. Ustream.tv. 7 January 2013. Retrieved 8 January 2013.</ref><ref name=kep/> Nel gennaio 2013 un gruppo di astronomi dell'[[Harvard-Smithsonian Center for Astrophysics]] ha stimato dai dati di Kepler che nella Via Lattea risiedano "almeno 17 miliardi" di esopianeti simili alla Terra.<ref name="Space-20130107">{{cite web |title=17 Billion Earth-Size Alien Planets Inhabit Milky Way |url=http://www.space.com/19157-billions-earth-size-alien-planets-aas221.html |date=7 January 2013 |publisher=[[Space.com]] |accessdate=8 January 2013 |author=Staff }}</ref>

|rowspan=2 style="border-top: 1px solid #aaa" |'''Composizione'''

| width="12%" style="border-top: 1px solid #aaa" |'''[[Pianeta terrestre|Pianeti terrestri]]'''

| width="88%" style="border-top: 1px solid #aaa" |[[Pianeta di silicio]] • [[Pianeta oceanico]] • [[Pianeta di carbonio]] • [[Pianeta di ferro]] • [[Pianeta senza nucleo]]

|- style="font-size: 90%"

| style="border-top: 1px solid #aaa" |'''Pianeti giganti'''

| style="border-top: 1px solid #aaa" |[[Gigante gassoso]] • [[Gigante di ghiaccio]] • [[Gigante di carbonio]] • [[Pianeta di elio]] • [[Pianeta ctonio]]

|- style="font-size: 90%"

Il [[programma Discovery]], di cui ''Kepler'' è parte, consiste in missioni scientifiche di basso costo focalizzate su obiettivi precisi. La costruzione del telescopio e le operazioni iniziali sono state gestite dal [[Jet Propulsion Laboratory]], insieme alla [[Ball Aerospace & Technologies Corp.|Ball Aerospace]], responsabile dello sviluppo del sistema di volo. L'[[Ames Research Center]] è invece responsabile dello sviluppo dei sistemi a Terra, delle operazioni di missione dal dicembre 2009 e dell'analisi dei dati scientifici.

| style="border-top: 1px solid #aaa" |'''Configurazione orbitale'''

Il tempo previsto per la missione è stato inizialmente di 3,5 anni, ma nel 2012 è stata estesa al 2016<ref Name="BBC7March">{{cite news |author=BBC Staff |title=Nasa launches Earth hunter probe |work=[[BBC News]] |date=7 March 2009 |url=http://news.bbc.co.uk/2/hi/science/nature/7926277.stm |accessdate=2009-03-14}}</ref><ref name=Space.com2016>[http://www.space.com/15160-alien-planet-kepler-mission-2016.html "NASA Extends Planet-Hunting Kepler Mission Through 2016"]. Space.com. 4 April 2012. Retrieved 2012-05-02.</ref>, in parte per difficoltà dovute all'analisi dell'enorme volume di dati raccolti dal telescopio.<ref>{{cite news |author=Stephen Clark |title=Kepler's exoplanet survey jeopardized by two issues|publisher=Spaceflight Now |date=16 October 2012|url=http://spaceflightnow.com/news/n1210/16kepler/ |accessdate=17 October 2012}}</ref>

| colspan=2 style="border-top: 1px solid #aaa" |[[Pianeta extrasolare]] • [[Luna extrasolare]] • [[Pianeta circumbinario]] • [[Pianeta doppio]] • [[Pianeti delle pulsar]] • [[Giove eccentrico|Gioviano eccentrico]] • [[Pianeta interstellare]] • [[Cometa interstellare]] • [[Pianeta extragalattico]]

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==Il telescopio spaziale ''Kepler''==

| style="border-top: 1px solid #aaa" |'''Distanza orbitale'''

[[Image:Keplerspacecraft-20110215.jpg|thumb|300px|Diagramma del telescopio che evidenzia i suoi principali componenti.]]

| colspan=2 style="border-top: 1px solid #aaa" |[[Pianeta di lava]] • [[Pianeta nettuniano caldo|Nettuniano caldo]] • [[Pianeta gioviano caldo|Gioviano caldo]] • [[Zona abitabile]] • [[Pianeta ghiacciato]] • [[Classificazione di Sudarsky]]

|-bgcolor="#003399"

Il telescopio possiede una massa di 1039 [[kilogrammo|kg]], ed è costituito da uno [[specchio primario]] di 1,4 [[metro|m]] di [[diametro]] e con un'[[apertura]] di 0,95 m, all'epoca del lancio il più grande mai mandato in orbita.<ref>{{cite web |last=Atkins |first=William |title=Exoplanet Search Begins with French Launch of Corot Telescope Satellite |url=http://www.itwire.com/content/view/8299/1066/ |publisher=iTWire |date=28 December 2008 |accessdate=2009-05-06}}</ref> Lo strumento ha un campo di vista di 115 gradi quadrati (circa 12° in diametro), equivalente all'area sottesa da un pugno a braccio teso, 105 dei quali utili per dati di qualità scientifica e con meno dell'11% di [[vignettatura]]. Il fotometro ha un effetto di [[soft focus]], per ottenere così misurazioni [[Fotometria|fotometriche]] eccellenti piuttosto che immagini nitide. L'obiettivo della missione è una precisione fotometrica differenziale combinata (''combined differential photometric precision'' o CDPP) di 20 [[parti per milione|ppm]] per una stella di magnitudine 12 di tipo solare e per un periodo di integrazione di 6,5 ore, anche se le osservazioni finora non hanno raggiunto questo obiettivo. Il transito di un [[pianeta terrestre]] produce una variazione di luminosità di 84 ppm e dura circa 13 ore.

! style="font-size: 90%;color:white" colspan=3 | <div style="text-align:center">[[File:Crystal Project konquest.png|15px|link=progetto:Astronomia]] <span style="color:white;">Questo box:&nbsp;&nbsp;&nbsp;&nbsp; [[template:Formazione stellare|<span style="color:white;">'''vedi'''</span>]] · [[template_talk:Formazione stellare|<span style="color:white;">'''disc.'''</span>]] · <span class="plainlinks">[{{fullurl:Template:Formazione stellare|action=edit}} <span style="color:white;">'''mod.'''</span>]</span></span></div>

|}

===Fotocamera===

[[File:Keplerspacecraft-FocalPlane-cutout.svg|thumb|left|La schiera di sensori di ''Kepler'': sono montati su una supericie curva per compensare la [[curvatura di campo di Petzval]].]]

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Il piano focale della fotocamera del telescopio è costituito da una matrice di 42 sensori [[Dispositivo a carica accoppiata|CCD]], ciascuno con una dimensione di 2200 × 1024 [[pixel]]. La fotocamera possiede quindi una risoluzione totale di 95 megapixel, il che la rende la più grande all'epoca mai lanciata nello spazio.<ref>{{cite web |author=NASA Staff |title=Kepler: Spacecraft and Instrument |url=http://www.nasa.gov/mission_pages/kepler/spacecraft/index.html |publisher=[[NASA]] |accessdate=2009-05-01}}</ref><ref>{{cite web |author=NASA Staff |title=Kepler's Diamond Mine of Stars |url=http://www.nasa.gov/mission_pages/kepler/multimedia/images/fullFFINoCalloutsHot300.html |publisher=[[NASA]] |date=16 April 2009 |accessdate=2009-05-01}}</ref> I sensori sono raffreddati da dei condotti termici ([[Heat pipe]]) connessi a un radiatore esterno.<ref name=presskit>{{cite journal |author=NASA Staff |url=http://www.nasa.gov/pdf/314125main_Kepler_presskit_2-19_smfile.pdf |title=Kepler: NASA's First Mission Capable of Finding Earth-Size Planets |publisher=[[NASA]] |date=February 2009 |accessdate=2009-03-14}}</ref>

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! style="color:white" colspan="3" align="center" | [[Pianeta extrasolare|<span style="color:white;">Pianeti extrasolari</span>]]

|- style="font-size: 90%"

I CCD sono letti ogni 6 secondi, per limitarne la saturazione, e le immagini sono generate a bordo dello strumento sommando per 30 minuti tali letture. Nonostante al lancio ''Kepler'' possedesse il più alto rateo di produzione di dati di qualsiasi altra missione NASA, l’immagine somma dei 95 milioni di pixel per 30 minuti costituisce più informazione di quanta possa essere memorizzata e trasmessa a Terra. Pertanto il team ha preselezionato i pixel associati a ciascuna stella di interesse, vale a dire il 5% del totale. I dati da questi pixel sono in seguito riquantificati, compressi e memorizzati, insieme a dati ausiliari, nell’unità di [[memoria a stato solido]] da 16 GB di bordo. I dati memorizzati e scaricati a Terra comprendono le immagini delle stelle del progetto, lo striscio, il livello di nero, il fondo e il pieno campo.<ref name="presskit"/>

| width="17%" |'''Formazione'''

| width="83%" |[[Disco protoplanetario]] • [[Planetesimo]] • [[Protopianeta]] • [[Sistema planetario]]

|rowspan=5 bgcolor="#003399"|[[File:Icy Exoplanet.jpg|180px]]

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===Storia della missione ===

| style="border-top: 1px solid #aaa" |'''Abitabilità'''

[[Image:Delta II with Kepler.jpg|thumb|upright|''Kepler'''s launch on 7 March 2009.]]

| style="border-top: 1px solid #aaa" |[[Zona abitabile]] • [[Analogo terrestre]] • [[Planetary Habitability Laboratory]] • [[Earth Similarity Index|ESI]]

Nel gennaio 2006 il lancio del telescopio è stato ritardato di otto mesi per via di tagli al bilancio della NASA,<ref name="MissionHistory">{{cite web |last=Borucki |first=W. J. |date=22 May 2010 |url=http://kepler.nasa.gov/Mission/QuickGuide/history/ |title=Brief History of the Kepler Mission |publisher=[[NASA]] |accessdate=2011-04-23}}</ref> e di altri quattro mesi nel marzo dello stesso anno per problemi fiscali.<ref name="MissionHistory"/> In questo periodo è stato cambiato il design dell’antenna ad alto guadagno, rinunciando alla [[sospensione cardanica]] e collegandola al direttamente al telaio del veicolo spaziale, così da ridurre costi e complessità, al costo di un giorno di osservazione al mese perso.<ref name="MissionHistory"/>

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Il telescopio spaziale ''Kepler'' è stato lanciato il 7 marzo 2009 alle 03:49:57&nbsp;UTC (6 marzo ore 10:49:57&nbsp;pm EST) a bordo di un lanciatore [[Delta II]] dalla [[Cape Canaveral Air Force Station]], Florida.<ref name=kasc>{{cite web |author=Aarhus University Staff |title=KASC Scientific Webpage | url=http://astro.phys.au.dk/KASC/ |publisher=[http://astro.phys.au.dk/KASC/ Kepler Asteroseismic Science Consortium] |date=14 March 2009 |accessdate=2009-03-14}}</ref><ref name="KeplerLaunch"/> Il lancio è stato un successo completo e tutte e tre le fasi erano complete alle 04:55&nbsp;UTC. La copertura del telescopio è stata espulsa il 7 aprile e le immagini di [[prima luce]] sono state scattate il giorno successivo.<ref>{{cite web |last=DeVore |first=Edna |url=http://www.space.com/searchforlife/090409-kepler-dust-cover.html |title=Planet-Hunting Kepler Telescope Lifts Its Lid |date=9 April 2009 |publisher=[http://www.space.com/ SPACE.com] |accessdate=2009-04-14}}</ref><ref>{{cite web |author=NASA Staff |url=http://www.nasa.gov/home/hqnews/2009/apr/HQ_09-085_Kepler_First_Light.html|title=NASA's Kepler Captures First Views of Planet-Hunting Territory |date=16 April 2009 |publisher=[[NASA]]|accessdate=2009-04-16}}</ref>

| style="border-top: 1px solid #aaa" |'''[[Metodi di individuazione di pianeti extrasolari|Metodi di scoperta]]'''

| style="border-top: 1px solid #aaa" |[[Metodi di individuazione di pianeti extrasolari#Direct Imaging|Direct Imaging]] • [[Metodo del transito|Transito]] • [[Metodo delle velocità radiali|Velocità radiali]] • [[Metodo delle microlenti gravitazionali|Microlensing]] • [[Metodi di individuazione di pianeti extrasolari#Variazioni degli intervalli di emissioni di una Pulsar|Pulsar timing]] • [[Metodi di individuazione di pianeti extrasolari#Astrometria|Astrometria]] • [[Polarimetria]] • [[Relativistic beaming]]

|- style="font-size: 90%"

Il 20 aprile 2009 il team scientifico di ''Kepler'' ha annunciato che ulteriori rifiniture del [[fuoco (ottica)|fuoco]] avrebbero incrementato notevolmente la qualità dei dati di ritorno.<ref>{{cite web |author=NASA Staff |url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20090420.html |title=04.20.09 – Kepler Mission Manager Update |date=20 April 2009 |publisher=[[NASA]] |accessdate=2009-04-20}}</ref> Il 23 aprile seguente è stato annunciato come il fuoco fosse stato ottimizzato con successo, muovendo lo specchio primario di 40 [[micrometro|micrometri]] verso il [[piano focale]] e inclinandolo di 0,0072 gradi.<ref>{{cite web |author=NASA Staff |url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20090424.html |title=04.23.09 – Kepler Mission Manager Update |date=23 April 2009 |publisher=[[NASA]] |accessdate=2009-04-27}}</ref>

| style="border-top: 1px solid #aaa" |'''Liste'''

| style="border-top: 1px solid #aaa" |[[Pianeti extrasolari confermati|Pianeti confermati]] • [[Stelle con pianeti extrasolari confermati|Stelle con pianeti confermati]] • [[Lista dei pianeti extrasolari non confermati o controversi|Controversi e non confermati]] • [[Lista dei pianeti scoperti dalla missione Kepler|Pianeti Kepler]] • [[Lista dei pianeti scoperti dal progetto SuperWASP|Pianeti SuperWASP]] • [[Lista dei pianeti scoperti dal progetto HATNet|Pianeti HATNet]] • [[Pianeti extrasolari notevoli|Scoperte notevoli e miliari]] • [[Lista dei pianeti potenzialmente abitabili|Potenzialmente abitabili]]

|- style="font-size:100%" align="center"

Il 13 maggio 2009 alle ore 01:01 UTC ''Kepler'' ha completato con successo la fase di commissioning e ha cominciato la sua ricerca di pianeti extrasolari.<ref name="Update20090514">{{cite web |author=NASA Staff | url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20090514.html |title=05.14.09 – Kepler Mission Manager Update |date=14 May 2009 |publisher=[[NASA]] |accessdate=2009-05-16}}</ref><ref>{{cite web | author=NASA Staff |title=Let the Planet Hunt Begin | url=http://www.nasa.gov/mission_pages/kepler/news/kepler-200905013.html | publisher=[[NASA]] |date=13 May 2009 |accessdate=2009-05-13}}</ref>

|colspan=2 style="border-top: 1px solid #aaa"|'''[[Classificazione dei pianeti extrasolari]]''' • '''[[Nomenclatura dei pianeti extrasolari]]'''

|-bgcolor="#003399"

Il 19 giugno 2009 il veicolo spaziale ha trasmesso con successo i suoi primi dati scientifici a Terra. Si è scoperto che il 15 giugno Kepler è entrato in "safe mode" (modalità di sicurezza), e una seconda volta il 2 luglio. Entrambi gli eventi sono stati innescati da un "reset del processore". Il telescopio è ritornato ad operare normalmente il 3 luglio, e i dati raccolti dal 19 giugno sono stati trasmessi a Terra quel giorno.<ref name="Update20090707">{{cite web |author=NASA Staff |url=http://kepler.nasa.gov/Mission/mmupdates/missionManagerArchive/ |title=2009 July 7 Mission Manager Update |date=7 July 2009 |publisher=[[NASA]] |accessdate=2011-04-23}}</ref> Il 14 ottobre 2009 si è determinato che la causa di questi eventi di “messa in sicurezza” del telescopio era un generatore di potenza a bassa tensione, che alimenta il processore [[RAD750]].<ref name="Update20091014">{{cite web |author=NASA Staff|url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20091014.html |title=Kepler Mission Manager Update |date=14 October 2009 |publisher=[[NASA]] |accessdate=2009-10-18}}</ref> IL 12 gennaio 2010 una porzione del piano focale ha trasmesso dati anomali, indicando un problema con il piano focale del modulo MOD-3, che controlla 2 dei 42 CCD di Kepler. Il modulo tuttora è dichiarato come non funzionante, ma la copertura eccede ancora gli obiettivi scientifici.<ref>{{cite web |author=NASA Staff |title=Kepler outlook positive; Followup Observing Program in full swing |url=http://kepler.nasa.gov/news/mmu/index.cfm?FuseAction=ShowNews&NewsID=55 |date=23 August 2010 |accessdate=2011-04-23}}</ref>

! style="font-size: 90%;color:white" colspan=3 | <div style="text-align:center">[[File:Crystal Project konquest.png|15px|link=progetto:Astronomia]] <span style="color:white;">Questo box:&nbsp;&nbsp;&nbsp;&nbsp; [[template:Formazione stellare|<span style="color:white;">'''vedi'''</span>]] · [[template_talk:Formazione stellare|<span style="color:white;">'''disc.'''</span>]] · <span class="plainlinks">[{{fullurl:Template:Formazione stellare|action=edit}} <span style="color:white;">'''mod.'''</span>]</span></span></div>

|}

Kepler scarica circa 12 gigabyte di dati<ref name="Update20090923">{{cite web |author=NASA Staff |url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20090923.html |title=Kepler Mission Manager Update |date=23 September 2009 |publisher=[[NASA]] |accessdate=2009-09-25}}</ref> all’incirca una volta al mese<ref name="Update20091105">{{cite web |author=NASA Staff |url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20091105.html |title=Kepler Mission Manager Update |date=5 November 2009 |publisher=[[NASA]] |accessdate=2009-11-08 }}</ref>, un esempio di tale download è quello del 22-23 novembre.<ref>{{cite web |author=NASA Staff |title=Data Download; Data Release; 2010 ground-based observing complete; AAS meeting |url=http://kepler.nasa.gov/news/mmu/index.cfm?FuseAction=ShowNews&NewsID=83 |date=6 December 2010 |accessdate=2010-12-21 }}</ref>

{| width="100%" align="center" style="margin-top:.5em; background:#CEDAF2; padding:5px; border:1px solid #003399; text-align:left"

Il 14 luglio 2012 una delle quattro [[ruota di reazione|ruote di reazione]] utilizzata per il puntamento fine del telescopio si è guastata.<ref>{{cite web |url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20122407.html |title=Kepler Mission Manager Update |date=24 July 2012 |author=Roger Hunter |publisher=NASA}}</ref> Seppur Kepler richieda solo tre delle ruote di reazione per posizionarsi accuratamente, il guasto ad un altra di queste renderebbe la sonda incapace di continuare la sua missione, e questa è una minaccia potenziale alla missione estesa.<ref>{{cite web |title=Kepler glitch may lower odds of finding Earth's twin |date=24 July 2012 |author=Maggie McKee |publisher=New Scientist |url=http://www.newscientist.com/article/dn22096-kepler-glitch-may-lower-odds-of-finding-earths-twin.html}}</ref>

|- bgcolor="#003399"

! style="color:white" colspan="4" align="center" | Ricerca dei [[Pianeta extrasolare|<span style="color:white;">pianeti extrasolari</span>]]

|- style="font-size: 90%"

Il 17 gennaio 2013 la NASA ha annunciato che una delle tre ruote di reazione rimanenti mostrava segni di frizione in aumento, e che Kepler avrebbe operato in modo discontinuo per 10 giorni come possibile soluzione al problema. Se anche la seconda ruota dovesse guastarsi la missione Kepler terminerebbe.<ref name="NASA-20130117">{{cite web |last=Hunter |first=Roger |title=Kepler Mission Manager Update |url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20130117.html |date=17 January 2013 |publisher=[[NASA]] |accessdate=18 January 2013 }}</ref><ref name="Marchis-20130117">{{cite web |last=Marchis |first=Franck |title=Kepler is Sick and Resting: 'Mountain View, we have a problem' |url=http://cosmicdiary.org/fmarchis/2013/01/17/kepler-is-damaged-and-now-resting-mountain-view-we-have-a-problem/ |date=17 January 2013 |publisher=Cosmic Diary |accessdate=18 January 2013 }}</ref> Il 29 gennaio la NASA ha annunciato il ritorno con successo alla normale modalità di raccolta dati.<ref name="NASA-20130129">{{cite web |last=Hunter |first=Roger |title=Kepler Mission Manager Update: Kepler Returns to Science Mode |url=http://www.nasa.gov/mission_pages/kepler/news/keplerm-20132901.html |date=29 January 2013 |publisher=[[NASA]] |accessdate=30 January 2013 }}</ref>

| width="11%" rowspan=3 style="border-top: 1px solid #aaa" |'''[[Osservatorio astronomico|Ricerca da Terra]]'''

| style="border-top: 1px solid #aaa" |'''[[Metodo delle velocità radiali|Velocità radiali]]'''

| style="border-top: 1px solid #aaa" |[[Anglo-Australian Planet Search|AAPS]] • [[Lick–Carnegie Exoplanet Survey|LCES]] • [[High Accuracy Radial Velocity Planet Searcher|HARPS]] e [[HARPS-N]], parte del [[Geneva Extrasolar Planet Search|GEPS]] • [[Magellan Planet Search Program|MPSP]] • [[East-Asian Planet Search Network|EAPSNet]] • [[HIRES]] • [[MARVELS]] • [[Automated Planet Finder|APF]]

|bgcolor="#003399" rowspan="6"|[[File:Telescope Kepler-NASA.jpeg|215px]]

|- style="font-size: 90%"

===Prestazioni===

| style="border-top: 1px solid #aaa" |'''[[Metodo del transito|Transito]]'''

In termini di prestazioni fotometriche ''Kepler'' sta lavorando bene, meglio di qualsiasi telescopio terrestre, seppure inferiormente all’obiettivo di progetto. Tale obiettivo era di una precisione fotometrica differenziale combinata (CDPP) di 20 [[parti per milione|ppm]] per una stella di magnitudine 12 in 6,5 ore di integrazione: questa stima era stata calcolata considerando una variabilità delle stelle di 10 ppm, all’incirca il valore di variabilità solare. L’accuratezza ottenuta invece per questo tipo di osservazione ha una vasta gamma di valori, in dipendenza dalla stella e dalla sua posizione sul piano focale, con una mediana di 29 ppm. Molto del rumore addizionale sembra essere dovuto a una maggiore variabilità delle stelle stesse, circa 19,5 ppm, mentre il resto è dovuto a fonti di rumore strumentale maggiori di quanto previsto.<ref>{{cite arxiv |last1=Gilliland |first1=Ronald L. |coauthors=''et al.'' |year=2011 |title= Kepler Mission Stellar and Instrument Noise Properties|class= astro-ph.SR|eprint=1107.5207}}</ref> Si sta lavorando per comprendere meglio il rumore strumentale ed eliminarlo.<ref>{{cite journal |last1=Caldwell |first1=Douglas A. |coauthors=''et al.'' |year=2010 |title=Kepler Instrument Performance: An In-Flight Update |journal=[[Proceedings of SPIE]] |volume=7731 |page=30 |url=http://kepler.nasa.gov/Science/ForScientists/papersAndDocumentation/SOCpapers/spie_2010_instrument_char_web_version.pdf |doi=10.1117/12.856638 |bibcode=2010SPIE.7731E..30C |series=Space Telescopes and Instrumentation 2010: Optical, Infrared, and Millimeter Wave |editor1-last=Oschmann, Jr |editor1-first=Jacobus M |editor2-last=Clampin |editor2-first=Mark C |editor3-last=MacEwen |editor3-first=Howard A}}</ref>

| style="border-top: 1px solid #aaa" |[[Progetto HATNet|HATNet]] • [[Progetto MEarth|MEarth]] • [[Progetto APACHE|APACHE]] • [[Progetto SuperWASP|SuperWASP]] • [[Trans-Atlantic Exoplanet Survey|TrES]] • [[Telescopio XO|XO]]

|- style="font-size: 90%"

Siccome il segnale di un [[pianeta terrestre]] transitante è molto vicino al livello di rumore (circa 80 ppm), l’aumento di questo implica per ogni singolo evento di transito un livello di significatività di 2,7 σ, invece del 4 σ di progetto. Questo a sua volta significa che più transiti devono essere necessariamente osservati per essere sicuri di una rivelazione di pianeta. Le stime scientifiche hanno indicato in 7-8 anni il tempo necessario alla missione per trovare tutti i pianeti terrestri transitanti, contro i 3,5 originalmente pianificati.<ref name="SandT">{{cite web |url=http://www.skyandtelescope.com/news/126242378.html |title=Kepler's Dilemma: Not Enough Time |publisher=Sky and Telescope |author=Kelly Beatty |date=September 2011}}</ref> Il 4 aprile 2012 è stata approvata la missione estesa di Kepler fino al'anno fiscale 2016.<ref name="mission extension">{{cite web |url=http://kepler.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=199 |title=NASA Approves Kepler Mission Extension |publisher=kepler.nasa.gov |author=News |date=4 April 2012}}</ref><ref name=Space.com2016/>

| style="border-top: 1px solid #aaa" |'''[[Metodo delle microlenti gravitazionali|Microlensing]]'''

| style="border-top: 1px solid #aaa" |[[Microlensing Observations in Astrophysics|MOA]] • [[Optical Gravitational Lensing Experiment|OGLE]] • [[MicroFUN]]

|- style="font-size: 90%"

===Spacecraft orbit and orientation===

| rowspan=3 style="border-top: 1px solid #aaa" |'''[[Telescopio spaziale|Ricerca dallo spazio]]'''

[[Image:LombergA1024.jpg|thumb|left|''Kepler's'' search volume, in the context of the Milky Way galaxy.]]

| width="12%" style="border-top: 1px solid #aaa" |'''Completate'''

[[Image:MilkywaykeplerfovbyCRoberts.jpg|thumb|right|The photometer's field of view in the constellations [[Cygnus (constellation)|Cygnus]], [[Lyra (constellation)|Lyra]] and [[Draco (constellation)|Draco]].]]

| width="88%" style="border-top: 1px solid #aaa" |[[EPOXI]] <small>(2005)</small> • [[SWEEPS]] <small>(2006)</small> • [[CoRoT]] <small>(2006-2013)</small>

''Kepler'' is in a [[heliocentric orbit]],<ref name="keplerlaunch1"/><ref>{{cite web |last1=Koch |first1=David |last2=Gould |first2=Alan |title=Kepler Mission: Launch Vehicle and Orbit |url=http://kepler.nasa.gov/sci/design/orbit.html |archiveurl=http://web.archive.org/web/20070622161529/http://kepler.nasa.gov/sci/design/orbit.html |archivedate=22 June 2007 |publisher=[[NASA]] |date=March 2009 | accessdate=2009-03-14}}</ref> which avoids Earth occultations, stray light, and [[gravity|gravitational]] perturbations and [[torque]]s inherent in an Earth orbit. The [[photometer]] points to a field in the [[Celestial coordinates|northern]] [[constellation]]s of [[Cygnus (constellation)|Cygnus]], [[Lyra (constellation)|Lyra]] and [[Draco (constellation)|Draco]], which is well out of the [[ecliptic]] plane, so that sunlight never enters the photometer as the spacecraft orbits the Sun. The field of view is not obscured by [[Kuiper belt]] objects or the [[asteroid belt]] either.<ref name=presskit/>

|- style="font-size: 90%"

This is also the direction of the Solar System's motion around the center of the galaxy. Thus, the stars which are observed by ''Kepler'' are roughly the same distance from the galactic center as the [[Solar System]], and also close to the galactic plane. This fact is important if position in the galaxy is related to habitability, as suggested by the [[Rare Earth hypothesis]].

| style="border-top: 1px solid #aaa" |'''In corso'''

| style="border-top: 1px solid #aaa" |[[Missione Kepler]] <small>(2009-)</small> • [[Satellite Gaia|GAIA]] <small>(2013-)</small>

|- style="font-size: 90%"

''Kepler'''s orbit has been described by NASA as Earth-trailing.<ref>{{cite web|url=http://www.nasa.gov/mission_pages/kepler/spacecraft/index-mission.html |title=Kepler: Spacecraft and Instrument |publisher=NASA |date= |accessdate=21 December 2011}}</ref> With an orbital period of 372.5 days, ''Kepler'' slowly falls further behind Earth.

| style="border-top: 1px solid #aaa" |'''Programmate'''

| style="border-top: 1px solid #aaa" |[[Transiting Exoplanet Survey Satellite|TESS]] <small>(2017)</small> • Proposte ([[Missione Plato|Plato]] • [[EChO]] • [[Exoplanetary Circumstellar Environments and Disk Explorer|EXCEDE]] • [[New Worlds Mission|New Worlds]]) • Cancellate ([[Missione Darwin|Darwin]] • [[Terrestrial Planet Finder|TPE]] • [[Missione Eddington|Eddington]] • [[Space Interferometry Mission|SIM]])

|-bgcolor="#003399"

===Spacecraft operations===

! style="font-size: 90%;color:white" colspan=4 | <div style="text-align:center">[[File:Crystal Project konquest.png|15px|link=progetto:Astronomia]] <span style="color:white;">Questo box:&nbsp;&nbsp;&nbsp;&nbsp; [[template:Formazione stellare|<span style="color:white;">'''vedi'''</span>]] · [[template_talk:Formazione stellare|<span style="color:white;">'''disc.'''</span>]] · <span class="plainlinks">[{{fullurl:Template:Formazione stellare|action=edit}} <span style="color:white;">'''mod.'''</span>]</span></span></div>

[[Image:Kepler orbit.png|thumb|right|''Kepler'''s orbit. The spacecraft's solar array is adjusted at [[solstice]]s and [[equinox]]es.]]

|}

''Kepler'' is operated out of [[Boulder, Colorado]], by the Laboratory for Atmospheric and Space Physics ([[LASP]]). The spacecraft's solar array is rotated to face the Sun at the [[solstice]]s and [[equinox]]es, so as to optimize the amount of sunlight falling on the solar array and to keep the heat radiator pointing towards deep space.<ref name=presskit/> Together, LASP and the spacecraft's builders, Ball Aerospace & Technologies Corp., control the spacecraft from a mission operations center located on the research campus of the [[University of Colorado at Boulder|University of Colorado]]. LASP performs essential mission planning and the initial collection and distribution of the science data. The mission's initial life-cycle cost was estimated at US$600 million, including funding for 3.5 years of operation.<ref name=presskit/> In 2012, NASA announced that the ''Kepler'' mission would be funded until 2016.<ref name=Space.com2016/>

<nowiki>

<noinclude>

====Communications====

[[Categoria:Template di navigazione - Astronomia|Formazione stellare]]

NASA contacts the spacecraft using the [[X band]] communication link twice a week for command and status updates. Scientific data are downloaded once a month using the [[Ka band|K_a band]] link at a maximum data transfer rate of approximately 550 KBps. The ''Kepler'' spacecraft conducts its own partial analysis on board and only transmits scientific data deemed necessary to the mission in order to conserve bandwidth.<ref>{{cite news |last=Ng |first=Jansen | url=http://www.dailytech.com/Kepler+Mission+Sets+Out+to+Find+Planets+Using+CCD+Cameras/article14421.htm |title=Kepler Mission Sets Out to Find Planets Using CCD Cameras | work=DailyTech |date=8 March 2009 |accessdate=2009-03-14}}</ref>

[[Categoria:Escludi dalla stampa|{{PAGENAME}}]]

</noinclude></nowiki>

====Data management====

Science data telemetry collected during mission operations at LASP is sent on for processing at the ''Kepler'' Data Management Center (DMC), located at the [[Space Telescope Science Institute]] on the campus of the [[Johns Hopkins University]] in [[Baltimore, Maryland]]. The science data telemetry is decoded and processed into uncalibrated [[FITS]]-format science data products by the DMC, which are then passed along to the Science Operations Center (SOC) at NASA Ames Research Center, for calibration and final processing. The SOC at NASA Ames Research Center (ARC) develops and operates the tools needed to process scientific data for use by the ''Kepler'' Science Office (SO). Accordingly, the SOC develops the pipeline data processing software based on scientific algorithms developed by the SO. During operations, the SOC:

#Receives calibrated pixel data from the DMC;

#Applies the analysis algorithms to produce light curves for each star;

#Performs transit searches for detection of planets (threshold-crossing events, or TCEs); and

#Performs data validation of candidate planets by evaluating various data products for consistency as a way to eliminate false positive detections.

The SOC also evaluates the photometric performance on an on-going basis and provides the performance metrics to the SO and Mission Management Office. Finally, the SOC develops and maintains the project’s scientific databases, including catalogs and processed data. The SOC finally returns calibrated data products and scientific results back to the DMC for long-term archiving, and distribution to astronomers around the world through the Multimission Archive at STScI (MAST).

==Field of view==

[[File:Kepler FOV hiRes.jpg|thumb|Diagram of ''Kepler'''s investigated area with [[celestial coordinates]].]]

<!--- [NOTE: Referred image does not seem to be posted??]

The image, shown to the right, is magnified detail from the full field of view image shown above. This image also identifies the [[TrES-2b]] system and clearly shows the parent [[binary star]], [[GSC 03549-02811]], in the [[constellation]] [[Draco (constellation)|Draco]].

--->

''Kepler'' has a fixed [[field of view]] (FOV) against the sky. The diagram to the right shows the [[celestial coordinates]] and where the detector fields are located, along with the locations of a few bright stars with [[celestial coordinates|celestial north]] at the top left corner. The mission website has a [http://kepler.nasa.gov/cgi-bin/ra2pix.pl calculator] that will determine if a given object falls in the FOV, and if so, where it will appear in the photo detector output data stream. Data on extrasolar planet candidates is submitted to the [[Kepler Follow-up Program]], or KFOP, to conduct follow-up observations.

Kepler's field of view covers 115 [[square degree]]s, around 0.28 percent of the sky, or "about two scoops of the Big Dipper". Thus, it would require around 400 Kepler-like telescopes to cover the whole sky relative to Earth.<ref>{{cite web |author=Ball Aerospace & Technologies |url=http://www.ballaerospace.com/page.jsp?page=186 |title=Kepler mission & program information|date= |publisher=[[Ball Aerospace & Technologies]] |accessdate=2012-09-18}}</ref>

==Objectives and methods==

The scientific objective of ''Kepler'' is to explore the structure and diversity of [[planetary systems]].<ref>{{cite web |last1=Koch |first1=David |last2=Gould |first2=Alan |title=Overview of the Kepler Mission | url=http://www.cfa.harvard.edu/kepler/papers/2004/SPIE.Glasgow.Koch.pdf | publisher=SPIE |year=2004 |accessdate=2010-12-09}}</ref> This spacecraft observes a large sample of stars to achieve several key goals:

* To determine how many Earth-size and larger planets there are in or near the [[habitable zone]] (often called "[[Goldilocks planet]]s")<ref name="Muir">{{cite news |last1=Muir |first1=Hazel |url=http://www.newscientist.com/article/dn11710 |title= 'Goldilocks' planet may be just right for life |work=[[New Scientist]] |date=25 April 2007 |accessdate=2009-04-02 }}</ref> of a wide variety of spectral types of stars.

* To determine the range of size and shape of the orbits of these planets.

* To estimate how many planets there are in multiple-star systems.

* To determine the range of orbit size, brightness, size, mass and density of short-period giant planets.

* To identify additional members of each discovered planetary system using other techniques.

* Determine the properties of those stars that harbor planetary systems.

Most of the [[extrasolar planet]]s previously detected by other projects were [[giant planet]]s, mostly the size of [[Jupiter]] and bigger. ''Kepler'' is designed to look for planets 30 to 600 times less massive, closer to the order of Earth's mass (Jupiter is 318 times more massive than Earth). The method used, the [[transit method]], involves observing repeated [[Astronomical transit|transit]] of planets in front of their stars, which causes a slight reduction in the star's [[apparent magnitude]], on the order of 0.01% for an Earth-size planet. The degree of this reduction in brightness can be used to deduce the diameter of the planet, and the interval between transits can be used to deduce the planet's orbital period, from which estimates of its orbital [[semi-major axis]] (using [[Kepler's laws#Third law|Kepler's laws]]) and its temperature (using models of stellar radiation) can be calculated.

The [[probability]] of a [[random]] [[Orbits of planets|planetary orbit]] being along the line-of-sight to a star is the diameter of the star divided by the diameter of the orbit.<ref name=geomprob>{{cite web |last1=Koch |first1=David |last2=Gould |first2=Alan |title=Kepler Mission: Characteristics of Transits (section "Geometric Probability") | url=http://jwleaf.org/docs/probability-of-planetary-transit.html | publisher=[[NASA]] |date=March 2009 |accessdate=2009-09-21 }}</ref> For an Earth-like planet at 1&nbsp;[[Astronomical unit|AU]] transiting a Sol-like star the probability is 0.465%, or about 1 in 215. At 0.72&nbsp;AU (the orbital distance of [[Venus]]) the probability is slightly larger, at 0.65%; such planets could be Earth-like if the host star is a [[stellar classification|late G-type star]] such as [[Tau Ceti]]. In addition, because planets in a given system tend to orbit in similar planes, the possibility of multiple detections around a single star is actually rather high. For instance, if a ''Kepler''-like mission conducted by aliens observed Earth transiting the Sun, there is a 12% chance that it would also see [[Venus]] transiting.

''Kepler''<nowiki>'</nowiki>s 115-deg² field of view gives it a much higher probability of detecting Earth-like planets than the [[Hubble Space Telescope]], which has a field of view of only [[Field of view#Astronomy|10 sq. arc-minutes]]. Moreover, ''Kepler'' is dedicated to detecting planetary transits, while the Hubble Space Telescope is used to address a wide range of scientific questions, and rarely looks continuously at just one starfield. Of the approximately half-million stars in ''Kepler'''s field of view, around 150,000 stars were selected for observation,<ref>{{cite arxiv |last1=Batalha |first1=Natalie M. |coauthors=''et al.'' |year=2010 |title=Selection, Prioritization, and Characteristics of Kepler Target Stars |class=astro-ph.SR |eprint=1001.0349}}</ref> and they are observed simultaneously, with the spacecraft measuring variations in their brightness every 30 minutes. This provides a better chance for seeing a transit. In addition, the 1-in-215 probability means that if 100% of stars observed had the same diameter as the Sun, and each had one Earth-like terrestrial planet in an orbit identical to that of the Earth, ''Kepler'' would find about 465; but if only 10% of stars observed were such, then it would find about 46. The mission is well suited to determine the frequency of Earth-like planets orbiting other stars.<ref name=presskit /><ref name="mission_faq">{{cite web |last1=Koch |first1=David |last2=Gould |first2=Alan |title=Kepler Mission: Frequently Asked Questions |url=http://kepler.nasa.gov/about/faq.html | archiveurl=http://web.archive.org/web/20070820000813/http://kepler.nasa.gov/about/faq.html |archivedate=20 August 2007 |publisher=[[NASA]] |date=March 2009 | accessdate=2009-03-14 }}</ref>

Since ''Kepler'' must see at least three transits to confirm that the dimming of a star was caused by a transiting planet, and since larger planets give a signal that is easier to check, scientists expected the first reported results to be larger Jupiter-size planets in tight orbits. The first of these were reported after only a few months of operation. Smaller planets, and planets farther from their sun will take longer, and discovering planets comparable to Earth is expected to take three years or longer.<ref name="keplerlaunch1">{{cite press release |author=NASA Staff |title=Kepler Mission Rockets to Space in Search of Other Earth | url=http://science.nasa.gov/headlines/y2009/06mar_keplerlaunch.htm?friend |publisher=[[NASA]] |date=6 March 2009 |accessdate=2009-03-14 }}</ref>

Once ''Kepler'' has detected a transit-like signature, it is necessary to rule out false positives with follow-up tests<ref>{{cite arxiv |last1=Batalha |first1=Natalie M. |coauthors=''et al.'' |year=2010 |title=Pre-Spectroscopic False Positive Elimination of Kepler Planet Candidates |class=astro-ph.EP |eprint=1001.0392}}</ref> such as [[doppler spectroscopy]]. Although ''Kepler'' was designed for photometry it turns out that it is capable of [[astrometry]] and such measurements can help confirm or rule out planet candidates.<ref>{{cite arxiv |last1=Monet |first1=David G. |coauthors=''et al.'' |year=2010 |title=Preliminary Astrometric Results from Kepler |class=astro-ph.IM |eprint=1001.0305}}</ref>

In addition to transits, planets orbiting around their stars undergo reflected light variations changes – like the [[Moon]], they go through [[Planetary phase|phases]] from full to new and back again. Since ''Kepler'' cannot resolve the planet from the star, it sees only the combined light, and the brightness of the host star seems to change over each orbit in a periodic manner. Although the effect is small – the photometric precision required to see a close-in giant planet is about the same as to detect an Earth-sized planet in transit across a solar-type star – Jupiter-sized planets are detectable by sensitive space telescopes such as ''Kepler''. In the long run, this method may help find more planets than the transit method, because the reflected light variation with orbital phase is largely independent of the planet's orbital inclination, and does not require the planet to pass in front of the disk of the star. In addition, the phase function of a giant planet is also a function of its thermal properties and atmosphere, if any. Therefore, the phase curve may constrain other planetary properties, such as the particle size distribution of the atmospheric particles.<ref>{{cite journal|last=Jenkins|first=J.M.|coauthors=Laurance R. Doyle|date=20 September 2003|title=Detecting reflected light from close-in giant planets using space-based photometers|journal=Astrophysical Journal|volume=1|issue=595|pages=429–445|doi=10.1086/377165|url = http://www.iop.org/EJ/article/0004-637X/595/1/429/56774.web.pdf|format = [[Portable Document Format|PDF]]|bibcode=2003ApJ...595..429J|arxiv = astro-ph/0305473 }}</ref>

Data collected by ''Kepler'' is also being used for studying [[variable stars]] of various types and performing [[asteroseismology]],<ref>{{cite arxiv |last1=Grigahcène |first1=A. |coauthors=''et al.'' |year=2010 |title=Hybrid γ Doradus – δ Scuti pulsators: New insights into the physics of the oscillations from ''Kepler'' observations |class=astro-ph.SR |eprint=1001.0747}}</ref> particularly on stars showing [[solar-like oscillations]].<ref>{{cite arxiv |last1=Chaplin |first1=W. J. |coauthors=''et al.'' |year=2010 |title=The asteroseismic potential of ''Kepler'': first results for solar-type stars |class=astro-ph.SR |eprint=1001.0506 }}</ref>

==Mission results to date==

[[File:329161main fullFFIHot300.png|thumb|left|A photo taken by ''Kepler'' with two points of interest outlined. [[celestial coordinates|Celestial north]] is towards the lower left corner.]]

[[File:Kepler329150main NGC6791.jpg|thumb|right|Detail of ''Kepler'''s image of the investigated area showing [[Open cluster|open star cluster]] [[NGC 6791]]. [[celestial coordinates|Celestial north]] is towards the lower left corner.]]

[[File:Kepler First Light Detail TrES-2.jpg|thumb|right|Detail of ''Kepler'''s image of the investigated area. The ___location of TrES-2b within this image is shown. [[celestial coordinates|Celestial north]] is towards the lower left corner.]]

The ''Kepler'' observatory is currently in active operation, with the [[Kepler Mission#Mission results to date|first main results]] announced on 4 January 2010. As expected, the initial discoveries were all short-period planets. As the mission continued, additional longer-period candidates were found.

===2009===

NASA held a press conference to discuss early science results of the Kepler mission on 6 August 2009.<ref name="KeplerBriefing20090806">{{cite web| url=http://www.nasa.gov/centers/ames/news/releases/2009/M09-94AR.html |author=NASA Staff |title=NASA Announces Briefing About Kepler's Early Science Results |date=3 August 2009 |publisher=[[NASA]] |accessdate=2011-04-23}}</ref> At this press conference, it was revealed that ''Kepler'' had confirmed the existence of the previously known transiting exoplanet [[HAT-P-7b]], and was functioning well enough to discover Earth-size planets.<ref name="KeplerPressConf20090806">{{cite web |author=NASA Staff |url=http://www.nasa.gov/mission_pages/kepler/news/kepler-discovery.html |title=NASA's Kepler Spies Changing Phases on a Distant World |date=6 August 2009 |publisher=[[NASA]] |accessdate=2009-08-06}}</ref><ref name=HATP7bScience>{{cite journal|title=Kepler's Optical Phase Curve of the Exoplanet HAT-P-7b|journal=[[Science (journal)|Science]] |date=7 August 2009 |last1=Borucki |first1=W. J. |coauthors=''et al.'' |volume=325 |issue=5941 |page=709 |doi= 10.1126/science.1178312 |pmid=19661420|bibcode=2009Sci...325..709B}}</ref>

Since ''Kepler'''s detection of planets depends on seeing very small changes in brightness, stars that vary in brightness all by themselves ([[variable star]]s) are not useful in this search.<ref name="Update20091105"/> From the first few months of data, ''Kepler'' scientists have determined that about 7,500 stars from the initial target list are such variable stars. These were dropped from the target list, and will be replaced by new candidates. On 4 November 2009, the ''Kepler'' project publicly released the light curves of the dropped stars.<ref>{{cite web |author=NASA Staff |url=http://archive.stsci.edu/mast_news.php?out=html&desc=t&id=342 |title=Kepler dropped stars now public |date=4 November 2009 |publisher=[[NASA]] |accessdate=2011-04-23}}</ref>

The first six weeks of data revealed five previously unknown planets, all very close to their stars.<ref name="sciencenews.org">{{cite web |author=ScienceNews Staff |url=http://www.sciencenews.org/view/generic/id/52465/title/Kepler_space_telescope_finds_its_first_extrasolar_planets |title=Kepler space telescope finds its first extrasolar planets |publisher=[[Sciencenews.org]] |date=30 January 2010 |accessdate=2011-02-05}}</ref><ref>{{cite web |last=MacRobert |first=Robert |title=Kepler's First Exoplanet Results – News Blog |url=http://www.skyandtelescope.com/community/skyblog/newsblog/80621797.html |publisher=[[Sky & Telescope]] |date=4 January 2010 |accessdate=2011-04-21}}</ref> Among the notable results are one of the least dense planets yet found,<ref name="centauri-dreams.org">{{cite web |last=Gilster |first=Paul |url=http://www.centauri-dreams.org/?p=16640 |title=The Remarkable Kepler-11 |publisher=[[Tau Zero Foundation]] |date=2 February 2011 |accessdate=2011-04-21}}</ref> two low-mass [[white dwarf]] stars<ref name="vanKerkwijk2010">{{cite journal |last1=van Kerkwijk |first1=Martin H. |coauthors=''et al.'' |title=Observations of Doppler Boosting in Kepler Light Curves |date=20 May 2010 |journal=[[The Astrophysical Journal]] |volume=715|issue=1 |pages=51–58 |bibcode=2010ApJ...715...51V |doi=10.1088/0004-637X/715/1/51|arxiv = 1001.4539 }}</ref> that were initially reported as being members of a new class of stellar objects,<ref name="hotter">{{cite web |last=Villard |first=Ray |title=Blazing Stellar Companion Defies Explanation |url=http://news.discovery.com/space/blazing-stellar-companion-defies-explanation.html |publisher=[[Discovery.com]] |accessdate=2011-04-20}}</ref> and a [[Kepler-16b|well-characterized planet orbiting a binary star]].

===2010===

On 15 June 2010, the Kepler mission released data on all but 400 of the ~156,000 planetary target stars to the public. 706 targets from this first data set have viable exoplanet candidates, with sizes ranging from as small as the Earth to larger than Jupiter. The identity and characteristics of 306 of the 706 targets were given. The released targets included 5 candidate multi-planet systems. Data for the remaining 400 targets with planetary candidates was to be released in February 2011. (For details about this later data release, see the ''Kepler'' results for [[Kepler (spacecraft)#2011|2011]] below.) Nonetheless, the ''Kepler'' results, based on the candidates in the list released in 2010, imply that most candidate planets have radii less than half that of Jupiter. The ''Kepler'' results also imply that small candidate planets with periods less than 30 days are much more common than large candidate planets with periods less than 30 days and that the ground-based discoveries are sampling the large-size tail of the size distribution.<ref name=Borucki2010>{{cite arxiv |eprint=1006.2799 |last1=Borucki |first1=William J. |coauthors=''et al.'' (Kepler Team) |title=Characteristics of Kepler Planetary Candidates Based on the First Data Set: The Majority are Found to be Neptune-Size and Smaller |class=astro-ph.EP |year=2010}}</ref> This contradicted older theories which had suggested small and Earth-like planets would be relatively infrequent.<ref name=history>{{cite journal |title=The Solar System: Its Origin and Evolution |last1=Woolfson |first1=M. M. |work=Physics Department, University of New York |journal=[[Royal Astronomical Society|Journal of the Royal Astronomical Society]] |volume=34 |pages=1–20 |year=1993 |bibcode=1993QJRAS..34....1W}} Page 18 in particular states that models that required a near collision of stars imply about 1% will have planets.</ref><ref>{{cite article |title=Protoplanet Migration by Nebula Tides |last1=Ward |first1=W.R. |journal=[[icarus (journal)|Icarus]] |volume=126 |issue=2, |pages=261—281 |year=1997

|url=http://www.gps.caltech.edu/classes/ge133/reading/ward_migration.pdf |publisher=[[Elsevier]] |accessdate=04-23-2011 }}</ref> Based on the ''Kepler'' data, an estimate of around 100 million habitable planets in our galaxy may be realistic.<ref>{{cite web |url=http://www.ted.com/talks/dimitar_sasselov_how_we_found_hundreds_of_earth_like_planets.html |last1=Sasselov |first1=Dimitar |title=How we found hundreds of Earth-like planets |publisher=[[Ted.com]] |date=July 2010 |accessdate=2011-02-05}}</ref> However, some media reports of the TED talk have led to misunderstandings, apparently partly due to confusion concerning the term "Earth-like". By way of clarification, a letter to the Director of the NASA [[Ames Research Center]], for the ''Kepler'' Science Council dated 2 August 2010 states, "Analysis of the current ''Kepler'' data does not support the assertion that ''Kepler'' has found any Earth-like planets."<ref>{{cite web |last1=Dunham |first1=Edward W. |last2=Gautier |first2=Thomas N. |last3=Borucki |first3=William J. |title=NASA Kepler Science Status: Statement to Ames Center Director |url=http://www.spaceref.com/news/viewsr.html?pid=34637 |date=3 August 2010 |accessdate=2011-04-24 }}</ref><ref>{{cite journal |last1=Steffen |first1=Jason H. |coauthors=''et al.'' |title=Five Kepler target stars that show multiple transiting exoplanet candidates |doi=10.1088/0004-637X/725/1/1226 |pages=1226–1241 |volume=725 |journal=[[Astrophysical Journal]] |arxiv=1006.2763 |date=9 November 2010 |bibcode = 2010ApJ...725.1226S}}</ref><ref>{{cite arxiv |last1=Prsa |first1=Andrej |coauthors=''et al.''|year=2010 |title=Kepler Eclipsing Binary Stars. I. Catalog and Principal Characterization of 1879 Eclipsing Binaries in the First Data Release |class=astro-ph.SR |eprint=1006.2815}}</ref>

In 2010, ''Kepler'' identified two systems containing objects which are smaller and hotter than their parent stars: [[KOI-74|KOI 74]] and [[KOI-81|KOI 81]].<ref>{{cite journal |last1=Rowe |first1=Jason F. |coauthors=''et al.'' |title=Kepler Observations of Transiting Hot Compact Objects |year=2010 |journal=[[The Astrophysical Journal Letters]] |volume=713 |issue=2 |pages=L150–L154 |bibcode=2010ApJ...713L.150R |doi=10.1088/2041-8205/713/2/L150|arxiv = 1001.3420 }}</ref> These objects are probably low-mass [[white dwarf]] stars produced by previous episodes of [[mass transfer]] in their systems.<ref name="vanKerkwijk2010"/>

In 2010, the ''Kepler'' team released a paper which had data for 312 extrasolar planet candidates from 306 separate stars. Only 33.5 days of data were available for most of the candidates.<ref name=Borucki2010/> NASA also announced data for another 400 candidates were being withheld to allow members of the ''Kepler'' team to perform follow-up observations.<ref>{{cite web |author=NASA Staff |title=Kepler News: First 43 Days of Kepler Data Released |url=http://kepler.arc.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=42 |publisher=[[NASA]] |date=15 May 2010 |accessdate=2011-04-24 }}</ref> The data for these candidates were made public on 2 February 2011.<ref name=borucki/>

===2011===

[[Image:Exoplanet Period-Mass Scatter Kepler.png|thumb|260px|A chart showing exoplanets in ''Kepler'''s FOV, in context of all discovered exoplanets (as of 2010-10-03), with some transit probabilities indicated for example scenarios.]]

On 2 February 2011, the ''Kepler'' team announced the results of analysis of the data taken between 2 May and 16 September 2009.<ref name=borucki>{{cite arxiv |last1=Borucki |first1=William J. |coauthors=''et al.'' |year=2011 |title=Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data |class=astro-ph.EP |eprint=1102.0541 }}</ref> They found 1235 planetary candidates circling 997 host stars. (The numbers that follow assume the candidates are really planets, though the official papers called them only candidates. Independent analysis indicated that at least 90% of them are real planets and not false positives).<ref>{{cite arxiv |last1=Morton |first1=Timothy D. |last2=Johnson |first2=John Asher |year=2011 |title=On the Low False Positive Probabilities of Kepler Planet Candidates |class=astro-ph.EP |eprint=1101.5630}}</ref> 68 planets were approximately Earth-size, 288 super-Earth-size, 662 Neptune-size, 165 Jupiter-size, and 19 up to twice the size of Jupiter. In contrast to previous work, roughly 74% of the planets are smaller than Neptune, most likely as a result of previous work finding large planets more easily than smaller ones.

That 2 February 2011 release of 1235 extrasolar planet candidates, included 54 that may be in the "[[habitable zone]]", including 5 less than twice the size of the Earth.<ref name=5earths>{{cite web |author=NASA Staff |title=NASA Finds Earth-size Planet Candidates in Habitable Zone, Six Planet System |url=http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=98 |date=2 February 2011 |publisher=[[NASA]] |accessdate=2011-04-24 }}</ref><ref name="Overbye">{{cite news |last1=Overbye |first1=Dennis |title=Kepler Planet Hunter Finds 1,200 Possibilities |publisher=New York Times |date=2 February 2011 |url=http://www.nytimes.com/2011/02/03/science/03planet.html |accessdate=2011-04-24 }}</ref> There were previously only two planets thought to be in the "habitable zone", so these new findings represent an enormous expansion of the potential number of "[[Goldilocks planet]]s" (planets of the right temperature to support liquid water).<ref Name="Borenstein">{{cite news |last1=Borenstein |first1=Seth |title=NASA spots scores of potentially livable worlds |publisher=[[msnbc.com|MSNBC News]] |date=2 February 2011 |url=http://msnbc.msn.com/id/41387915/ns/technology_and_science-space |accessdate=2011-04-24 }}</ref> All of the habitable zone candidates found thus far orbit stars significantly smaller and cooler than the Sun (habitable candidates around Sun-like stars will take several additional years to accumulate the three transits required for detection).<ref name = "Alexander">{{cite web |last1=Alexander |first1=Amir |title = Kepler Discoveries Suggest a Galaxy Rich in Life |work=[http://www.planetary.org/home/ The Planetary Society web site] |publisher=[[The Planetary Society]] |date=3 February 2011 |url= http://www.planetary.org/news/2011/0203_Kepler_Discoveries_Suggest_a_Galaxy.html |accessdate = 2011-02-04}}</ref> Of all the new planet candidates, 68 are 125% of [[Earth]]'s size or smaller, or smaller than all previously discovered exoplanets.<ref name="Overbye" /> "Earth-size" and "super-Earth-size" is defined as "less than or equal to 2 Earth radii (Re)" [(or, Rp ≤ 2.0 Re) – Table 5].<ref name=borucki/> Six such planet candidates [namely: KOI 326.01 (Rp=0.85), KOI 701.03 (Rp=1.73), KOI 268.01 (Rp=1.75), KOI 1026.01 (Rp=1.77), KOI 854.01 (Rp=1.91), KOI 70.03 (Rp=1.96) – Table 6]<ref name=borucki/> are in the "habitable zone."<ref name=5earths /> A more recent study found that one of these candidates (KOI&nbsp;326.01) is in fact much larger and hotter than first reported.<ref name=Grant>{{cite web |last1=Grant |first1=Andrew |title=Exclusive: "Most Earth-Like" Exoplanet Gets Major Demotion—It Isn't Habitable |url=http://blogs.discovermagazine.com/80beats/2011/03/08/exclusive-most-earth-like-exoplanet-gets-major-demotion%e2%80%94it-isnt-habitable/ |publisher=[[Discover Magazine]] |work=[http://blogs.discovermagazine.com/80beats 80beats] |date=8 March 2011|accessdate=2011-04-24 }}</ref>

The frequency of planet observations was highest for exoplanets two to three times Earth-size, and then declined in inverse proportionality to the area of the planet. The best estimate (as of March 2011), after accounting for observational biases, was: 5.4% of stars host Earth-size candidates, 6.8% host super-Earth-size candidates, 19.3% host Neptune-size candidates, and 2.55% host Jupiter-size or larger candidates. Multi-planet systems are common; 17% of the host stars have multi-candidate systems, and 33.9% of all the planets are in multiple planet systems.<ref>{{cite journal |first=William J. |last=Borucki |coauthors=''et al.'' |year=2011 |title=Characteristics of planetary candidates observed by Kepler, II: Analysis of the first four months of data |arxiv=1102.0541 |bibcode = 2011ApJ...736...19B |doi = 10.1088/0004-637X/736/1/19|journal=The Astrophysical Journal |volume=736 |page=19 }}</ref>

[[File:Kepler 20 - planet lineup.jpg|thumb|left|220px|A size comparison of the exoplanets [[Kepler-20e]]<ref name="Kepler20e-20111220" /> and [[Kepler-20f]]<ref name="Kepler20f-20111220" /> with [[Venus]] and [[Earth]].]]

By 5 December 2011, the ''Kepler'' team announced that they had discovered 2,326 planetary candidates, of which 207 are similar in size to Earth, 680 are super-Earth-size, 1,181 are Neptune-size, 203 are Jupiter-size and 55 are larger than Jupiter. Compared to the February 2011 figures, the number of Earth-size and super-Earth-size planets increased by 200% and 140% respectively. Moreover, 48 planet candidates were found in the habitable zones of surveyed stars, marking a decrease from the February figure; this was due to the more stringent criteria in use in the December data.<ref name=KeplerDec2011Results/>

On 20 December 2011, the ''Kepler'' team announced the discovery of the first [[Terrestrial planet|Earth-size]] [[exoplanets]], [[Kepler-20e]]<ref name="Kepler20e-20111220" /> and [[Kepler-20f]],<ref name="Kepler20f-20111220" /> orbiting a [[Solar analog|Sun-like star]], [[Kepler-20]].<ref name="NASA-20111220" />

Based on ''Kepler'''s findings, astronomer [[Seth Shostak]] estimated in 2011 that "within a thousand light-years of Earth", there are "at least 30,000" habitable planets.<ref name="Shostak">{{cite news |last1=Shostak |first1=Seth |title=A Bucketful of Worlds |work=[[Huffington Post]] |date=3 February 2011 |url=http://www.huffingtonpost.com/seth-shostak/a-bucketful-of-worlds_b_817921.html |accessdate=2011-04-24 }}</ref> Also based on the findings, the ''Kepler'' team has estimated that there are "at least 50 billion planets in the Milky Way", of which "at least 500 million" are in the [[habitable zone]].<ref name="BorensteinS">{{cite news |last1=Borenstein |first1=Seth |title=Cosmic census finds crowd of planets in our galaxy |agency=Associated Press |date=19 February 2011 |url=http://apnews.excite.com/article/20110219/D9LG45NO0.html |accessdate=2011-04-24 }}</ref> In March 2011, astronomers at NASA's [[Jet Propulsion Laboratory]] (JPL) reported that about "1.4&nbsp;to 2.7 percent" of all sunlike stars are expected to have earthlike planets "within the [[habitable zone]]s of their stars". This means there are "two billion" of these "Earth analogs" in our own Milky Way galaxy alone. The JPL astronomers also noted that there are "50 billion other galaxies", potentially yielding more than one [[sextillion]] "Earth analog" planets if all galaxies have similar numbers of planets to the Milky Way.<ref name="ChoiCQ">{{cite web |last1=Choi |first1=Charles Q. |url=http://www.space.com/11188-alien-earths-planets-sun-stars.html |title=New Estimate for Alien Earths: 2 Billion in Our Galaxy Alone |date=21 March 2011 |publisher=[[Space.com]] |accessdate=2011-04-24}}</ref>

===2012===

In January 2012, an international team of astronomers reported that each star in the [[Milky Way Galaxy]] may host " [[exoplanet|on average...at least 1.6 planets]]", suggesting that over 160 billion star-bound planets may exist in our galaxy alone.<ref name="Space-20120111">{{cite web |last=Wall |first=Mike |title=160 Billion Alien Planets May Exist in Our Milky WayGalaxy |url=http://www.space.com/14200-160-billion-alien-planets-milky-galaxy.html |date=11 January 2012 |publisher=[[Space.com]] |accessdate=2012-01-11 }}</ref><ref name="Nature-20120111">{{cite journal |author=Cassan, A et al |title=One or more bound planets per Milky Way star from microlensing observations |url=http://www.nature.com/nature/journal/v481/n7380/full/nature10684.html |doi=10.1038/nature10684 |date=11 January 2012 |journal=[[Nature (journal)|Nature]] |volume=481 |pages=167–169 |accessdate=2012-01-11 |bibcode = 2012Natur.481..167C |pmid=22237108 |issue=7380|arxiv = 1202.0903 |last2=Kubas |first2=D. |last3=Beaulieu |first3=J.-P. |last4=Dominik |first4=M. |last5=Horne |first5=K. |last6=Greenhill |first6=J. |last7=Wambsganss |first7=J. |last8=Menzies |first8=J. |last9=Williams |first9=A. }}</ref> ''Kepler'' also recorded distant [[Solar flare|stellar super-flares]], some of which are 10,000 times more powerful than the superlative 1859 [[Carrington event]].<ref name=bbc1>{{cite news |url=http://www.bbc.co.uk/news/science-environment-18089695 |title=Kepler telescope studies star superflares |publisher=BBC News |date=17 May 2012 |accessdate=2012-05-31}}</ref> The superflares may be triggered by close-orbiting [[Jupiter]]-sized planets.<ref name=bbc1/> The [[Transit Timing Variation]] (TTV) technique, which was used to discover [[Kepler-9d]], gained popularity for confirming exoplanet discoveries.<ref>[http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=226 The Transit Timing Variation (TTV) Planet-finding Technique Begins to Flower]. NASA.gov.</ref> A planet in a system with four stars was also confirmed, the first time such a system had been discovered.<ref>[http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=233 Planet Hunters Find Circumbinary Planet in 4-Star System – 10.16.2012].</ref>

[[File:717582main NewCandidatesbySize-07Jan13 full.jpg|thumb|400px|right|Sizes of Kepler Planet Candidates - based on 2,740 candidates orbiting 2,036 stars {{As of|2013|01|07|lc=on}} (NASA).]]

{{As of|2012}}, there were [[List of planets discovered by the Kepler spacecraft|a total of 2,321 candidates]].<ref name=KeplerDec2011Results>{{cite web |url=http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=165 |title=Kepler-22b, Super-Earth in the habitable zone of a Sun-like Star |work=Kepler |publisher=NASA |date=5 December 2011}}</ref><ref>{{cite web |url=http://news.sciencemag.org/sciencenow/2011/09/super-earth-found-in-habitable-z.html |title='Super-Earth' Found in Habitable Zone |author=Govert Schilling |date=12 September 2011 |publisher=AAAS}}</ref><ref>{{cite web|url=http://archive.stsci.edu/kepler/planet_candidates.html|title=Released Kepler Planetary Candidates|publisher=MAST|date=27 February 2012|accessdate=26 November 2012}}</ref> Of these, 207 are similar in size to Earth, 680 are super-Earth-size, 1,181 are Neptune-size, 203 are Jupiter-size and 55 are larger than Jupiter. Moreover, 48 planet candidates were found in the habitable zones of surveyed stars. The ''Kepler'' team estimated that 5.4% of all stars host Earth-size planet candidates, and that 17% of all stars have multiple planets. In December 2011, two of the [[Terrestrial planet|Earth-sized]] candidates, [[Kepler-20e]]<ref name="Kepler20e-20111220">{{cite web |author=[[NASA|NASA Staff]] |title=Kepler: A Search For Habitable Planets – Kepler-20e |url=http://kepler.nasa.gov/Mission/discoveries/kepler20e/ |date=20 December 2011 |publisher=[[NASA]] |accessdate=2011-12-23 }}</ref> and [[Kepler-20f]],<ref name="Kepler20f-20111220">{{cite web |author=[[NASA|NASA Staff]] |title=Kepler: A Search For Habitable Planets – Kepler-20f |url=http://kepler.nasa.gov/Mission/discoveries/kepler20f/ |date=20 December 2011 |publisher=[[NASA]] |accessdate=2011-12-23 }}</ref> were confirmed as planets orbiting a [[Solar analog|Sun-like star]], [[Kepler-20]].<ref name="NASA-20111220">{{cite web |last=Johnson |first=Michele |title=NASA Discovers First Earth-size Planets Beyond Our Solar System|url=http://www.nasa.gov/mission_pages/kepler/news/kepler-20-system.html|publisher=[[NASA]] |date=20 December 2011 |accessdate=2011-12-20}}</ref><ref name="Nature-20111220">{{cite journal |last=Hand |first=Eric |title=Kepler discovers first Earth-sized exoplanets |doi=10.1038/nature.2011.9688 |date=20 December 2011 |journal=[[Nature (journal)|Nature]] }}</ref><ref name="NYT-20111220">{{cite news |last=Overbye |first=Dennis |title=Two Earth-Size Planets Are Discovered |url=http://www.nytimes.com/2011/12/21/science/space/nasas-kepler-spacecraft-discovers-2-earth-size-planets.html |date=20 December 2011 |publisher=[[New York Times]] |accessdate=2011-12-21 }}</ref>

===2013===

According to a study by [[Caltech]] astronomers published in January 2013, the [[Milky Way Galaxy]] contains at least one planet per star, resulting in 100 - 400 billion [[exoplanets]].<ref name="NASA-20130103">{{cite web |last=Claven|first=Whitney |title=Billions and Billions of Planets |url=http://www.nasa.gov/mission_pages/kepler/news/kepler20130103.html|date=3 January 2013 |publisher=[[NASA]] |accessdate=3 January 2013 }}</ref><ref name="Space-20130102">{{cite web |title=100 Billion Alien Planets Fill Our Milky Way Galaxy: Study |url=http://www.space.com/19103-milky-way-100-billion-planets.html |date=2 January 2013 |publisher=[[Space.com]] |accessdate=3 January 2013 |author=Staff }}</ref> The study, based on planets orbiting the star ''Kepler-32'', suggests that [[planetary systems]] may be common around stars in our galaxy. The discovery of 461 more planets was announced on 7 January 2013.<ref name=kep>[http://www.nasa.gov/mission_pages/kepler/news/kepler-461-new-candidates.html NASA's Kepler Mission Discovers 461 New Planet Candidates]</ref> The longer Kepler watches, the more planets with long periods it can detect.<ref name=kep/>

{{quote|Since the last Kepler catalog was released in February 2012, the number of candidates discovered in the Kepler data has increased by 20 percent and now totals 2,740 potential planets orbiting 2,036 stars.|NASA<ref name=kep/>}}

A new candidate, announced on 7 January 2013, is [[KOI-172.02]], an [[Earth]]-like [[exoplanet]] orbiting a [[star]] similar to our [[Sun]] in the [[habitable zone]] and possibly a "prime candidate to host [[extraterrestrial life|alien life]]".<ref name="Space-20130109">{{cite web |last=Moskowitz |first=Clara |title=Most Earth-Like Alien Planet Possibly Found |url=http://www.space.com/19201-most-earth-like-alien-planet.html |date=9 January 2013 |publisher=[[Space.com]] |accessdate=9 January 2013 }}</ref>

==Data releases==

The ''Kepler'' team originally promised to release data within one year of observations.<ref>{{cite web |url=http://kepler.nasa.gov/Mission/QuickGuide/faq/#a9 |title=Frequently Asked Questions from the Public |accessdate=6 September 2011}} This Kepler FAQ states: "Data for each 3-month observation period will be made public within one year of the end the observation period".</ref> However, this plan was changed after launch, with data being scheduled for release up to three years after its collection.<ref name=release>{{cite web|title=NASA's Kepler Mission Data Release Schedule|url=http://keplergo.arc.nasa.gov/ArchiveSchedule.shtml|publisher=[[NASA]]|accessdate=18 October 2011}} On this schedule, the data from the quarter ending June 2010 was scheduled to be released in June 2013.</ref> This resulted in considerable criticism,<ref>{{cite news |title=In the Hunt for Planets, Who Owns the Data? |author=Dennis Overbye |url=http://www.nytimes.com/2010/06/15/science/space/15kepler.html |publisher=New York Times |date=14 June 2010}}</ref><ref>{{cite web |url=http://www.nature.com/news/2010/100414/full/news.2010.182.html |title=Telescope team may be allowed to sit on exoplanet data |author=Eric Hand |publisher=Nature |date=14 April 2010 }}</ref><ref>{{cite web |url=http://www.skyandtelescope.com/news/home/122602884.html |title=Kepler's Exoplanets: A Progress Report |author= Alan MacRobert |date=August 2011 |publisher=S ky and Telescope}}</ref><ref>{{cite web |title=Minutes of the Kepler Users Panel |url=http://keplergo.arc.nasa.gov/docs/KUP_minutes_Mar2011.pdf |date=28–29 March 2011 |author=Alex Brown}}</ref><ref>{{cite web |url=http://news.discovery.com/space/kepler-exoplanet-controversy-erupts.html |title=KEPLER EXOPLANET CONTROVERSY ERUPTS |author=Nicole Gugliucci |date=15 June 2010 |publisher=Discovery news}}</ref> leading the ''Kepler'' science team to release the third quarter of their data one year and nine months after collection.<ref>{{cite web |url=http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=145 |title=NASA's Kepler Mission Announces Next Data Release to Public Archive}}</ref> The data through September 2010 (quarters 4, 5, and 6) was made public in January 2012.<ref>{{cite web |url=http://keplergo.arc.nasa.gov/ArchiveSchedule.shtml|title= Kepler Data Collection and Archive Timeline|accessdate=1 January 2012}}</ref>

===Follow-ups by others===

Periodically, the ''Kepler'' team releases a list of candidates ([[Kepler Object of Interest|Kepler Objects of Interest]], or KOIs) to the public. Using this information, a team of astronomers collected [[radial velocity]] data using the [[SOPHIE échelle spectrograph]] to confirm the existence of the candidate [[KOI-428b]] in 2010.<ref name="exoplanet1">{{cite web |last1=Santerne |first1=A. |coauthors=''et al.'' |url=http://exoplanet.eu/papers/koi428-vf.3.pdf |title=SOPHIE velocimetry of Kepler transit candidates II. KOI-428b: a hot Jupiter transiting a subgiant F-star |date=30 November 2010 |accessdate=2011-04-23 }}</ref> In 2011, the same team confirmed candidate [[KOI-423b]].<ref name="exoplanet2">{{cite arxiv |last1=Bouchy|first1=F. |coauthors=''et al.'' |year=2011 |title= SOPHIE velocimetry of Kepler transit candidates III. KOI-423b: An 18 Mjup transiting companion around an F7IV star|class= astro-ph.EP|eprint=1106.3225}}</ref>

===Citizen scientist participation===

Since December 2010, ''Kepler'' mission data has been used for the [[Zooniverse (citizen science project)|Zooniverse]] project "Planethunters.org", which allows volunteers to look for transit events in the light curves of ''Kepler'' images to identify planets that computer [[algorithm]]s might miss.<ref>{{cite web |last1=Andrews |first1=Bill |title=Become a Planet Hunter! |url=http://cs.astronomy.com/asycs/blogs/astronomy/archive/2010/12/20/become-a-planet-hunter.aspx |publisher=[[Astronomy (magazine)|Astronomy]] |date=20 December 2010 |accessdate=2011-04-24 }}</ref> By June 2011, users had found 69 potential candidates that were previously unrecognized by the ''Kepler'' mission team.<ref>{{cite web |author=Zooniverse Staff |title=Planetometer |url=http://www.planethunters.org/planetometer |publisher=[[Zooniverse (citizen science project)|Zooniverse]] |accessdate=2011-06-15 }}</ref> The team has plans to publicly credit amateurs who spot such planets.

In January 2012, the [[British Broadcasting Corporation]] (BBC) program ''[[Stargazing Live]]'' aired a public appeal for volunteers to analyse Planethunters.org data for potential new exoplanets. This led to the discovery of a new [[Neptune]]-sized exoplanet by two amateur astronomers – one in [[Peterborough]], [[England]] – to be named Threapleton Holmes B.<ref>{{cite news|last= |first= |url=http://www.telegraph.co.uk/science/space/9026837/Amateur-stargazers-discover-new-planet.html |work=[[The Daily Telegraph]] |title=Amateur stargazers discover new planet |publisher=[[Telegraph Media Group]] |date=20 January 2012 |accessdate=20 January 2012}}</ref> 100,000 other volunteers were reportedly engaged in the search by late January, analysing over 1 million ''Kepler'' images.<ref>{{cite news |url=http://www.bbc.co.uk/news/science-environment-16612181 |title=Stargazing viewer in planet coup |publisher=BBC News |date=18 January 2012 |accessdate=2012-01-19}}</ref>

==Mission status==

In April 2012, an independent panel of senior NASA scientists recommended that the ''Kepler'' mission be continued through 2016. According to the senior review, ''Kepler'' observations needed to continue until at least 2015 to achieve all the stated scientific goals.<ref>{{cite web |last1=Clark |first1=stephen |url=http://www.spaceflightnow.com/news/n1204/04kepler/ |title=Kepler planet-hunting mission extended until 2016 |date=4 April 2012 |publisher=Spaceflight anow |accessdate=2012-04-04}}</ref> On 14 November 2012, NASA announced the completion of Kepler's primary mission, and the beginning of its extended mission, which may last as long as four years.<ref>{{cite web|title=Release : 12–394 – NASA's Kepler Completes Prime Mission, Begins Extended Mission|url=http://www.nasa.gov/home/hqnews/2012/nov/HQ_12-394_Kepler_Completes_Prime_Mission.html|publisher=NASA|accessdate=17 November 2012}}</ref>

==Confirmed exoplanets==

[[File:Kepler first five exoplanet size.jpg|thumb|''Kepler''{{'}}s first five [[exoplanets]] to scale.]]

{{see also|List of planets discovered by the Kepler spacecraft|list of exoplanetary host stars|list of planetary systems}}

In addition to discovering hundreds of exoplanet candidates, the ''Kepler'' spacecraft has also reported 26 exoplanets in 11 systems which have not yet been added to the Extrasolar Planet Database.<ref name=11-new-solar-systems>{{cite news|last=O'Neill|first=Ian|title=11 New Alien Solar Systems Crammed with Exoplanets|url=http://news.discovery.com/space/11-new-alien-solar-systems-crammed-with-exoplanets-120126.html|accessdate=26 January 2012|newspaper=Discovery News|date=26 January 2012}}</ref> Exoplanets discovered using ''Kepler''<nowiki>'</nowiki>s data, but confirmed by outside researchers, include [[KOI-423b]],<ref name="exoplanet2"/> [[KOI-428b]],<ref name="exoplanet1"/> [[KOI-196b]],<ref name=KOI-196b>{{cite web|author=cyril DEDIEU |url=http://exoplanet.eu/star.php?st=KOI-196 |title=Star: KOI-196 |publisher=Extrasolar Planets Encyclopaedia |date= |accessdate=21 December 2011}}</ref> [[KOI-135b]],<ref name=KOI-135b>{{cite web|author=|url=http://exoplanet.eu/star.php?st=KOI-135 |title=Star: KOI-135 |publisher=Extrasolar Planets Encyclopaedia |date= |accessdate= 2011}}</ref> [[KOI-204b]],<ref name=KOI-204b>{{cite web|author=|url=http://exoplanet.eu/star.php?st=KOI-204 |title=Star: KOI-204 |publisher=Extrasolar Planets Encyclopaedia |date= |accessdate= 2011}}</ref> [[KOI-254b]],<ref name=KOI-254b>{{cite web|author=|url=http://exoplanet.eu/star.php?st=KOI-254 |title=Star: KOI-254 |publisher=Extrasolar Planets Encyclopaedia |date= |accessdate= 2011}}</ref> [[KOI-730]],<ref name=KOI-730>{{cite web|author=|url=http://exoplanet.eu/star.php?st=KOI-730 |title=Star: KOI-730 |publisher=Extrasolar Planets Encyclopaedia |date= |accessdate= 2011}}</ref> and [[Kepler-42|Kepler-42 (KOI-961)]].<ref name=KOI-961>{{cite web|author=|url=http://exoplanet.eu/star.php?st=KOI-961 |title=Star: KOI-961 |publisher=Extrasolar Planets Encyclopaedia |date= |accessdate= 2012}}</ref> The "KOI" acronym indicates that the star is a ''K''epler ''O''bject of ''I''nterest.

Both Corot<ref>{{cite journal

|title=The changing phases of extrasolar planet CoRoT-1b

|last1=Snellen |first1=I.A.G.

|last2=De Mooij |first2=E.J.W.

|last3=Albrecht |first3=S.

|journal=Nature

|volume=459

|issue=7246

|pages=543–545

|year=2009

|doi=10.1038/nature08045

|bibcode = 2009Natur.459..543S

|pmid=19478779

|arxiv = 0904.1208}} [http://arxiv.org/abs/0904.1208 Preprint from arxiv.]</ref> and ''Kepler''<ref name="kepler_phases">{{cite journal | author = Borucki, W.J. et al. | title = Kepler's Optical Phase Curve of the Exoplanet HAT-P-7b | journal = Science | volume = 325 | issue = 5941 | pages = 709 | year = 2009 | doi = 10.1126/science.1178312 | bibcode = 2009Sci...325..709B | pmid = 19661420 | last2 = Koch | first2 = D. | last3 = Jenkins | first3 = J. | last4 = Sasselov | first4 = D. | last5 = Gilliland | first5 = R. | last6 = Batalha | first6 = N. | last7 = Latham | first7 = D. W. | last8 = Caldwell | first8 = D. | last9 = Basri | first9 = G.}}</ref> measured the reflected light from planets. However, these planets were already known, since they transit their host star. ''Kepler'''s data allowed the first discovery of planets by this method, KOI 55.01 and 55.02.<ref>{{cite article |title=A compact system of small planets around a former red-giant star

|author=Charpinet, S. and Fontaine, G. and Brassard, P. and Green, EM and Van Grootel, V. and Randall, SK and Silvotti, R. and Baran, AS and Østensen, RH and Kawaler, SD and others

|journal=Nature

|volume=480

|issue=7378

|pages=496—499

|year=2011

|publisher=Nature Publishing Group

|doi=10.1038/nature10631

|url=http://www.nature.com/nature/journal/v480/n7378/full/nature10631.html }}</ref>

==''Kepler'' Input Catalog==

{{Main|Kepler Input Catalog}}

The '''Kepler Input Catalog''' (or '''KIC''') is a publicly searchable database of roughly 13.2 million targets used for the [http://archive.stsci.edu/mast_faq.php?mission=KEPLER#45 Kepler Spectral Classification Program] and ''Kepler'' Mission.<ref name=kic>{{cite web |author=NASA Staff |url=http://archive.stsci.edu/kepler/kic10/help/search_help.html |title=MAST KIC Search Help |publisher=[[Space Telescope Science Institute]] |date= |accessdate=2011-04-23}}</ref><ref>{{cite web |author=NASA Staff |url=http://archive.stsci.edu/kepler/kic10/search.php |title=KIC10 Search |accessdate=2011-04-23}}</ref> The catalog alone is not used for finding ''Kepler'' targets, because only a portion of the listed stars (about one-third of the catalog) can be observed by the spacecraft itself.<ref name=kic/>

==Voci correlate==

{{MultiCol}}

*[[Lista dei pianeti scoperti dalla missione Kepler]]

*[[Lista dei pianeti extrasolari confermati]]

*[[Lista dei pianeti extrasolari non confermati o controversi]]

*[[Kepler-11]]

*[[Kepler-16 (AB)b]]

*[[Kepler-22 b]]

*[[Kepler-47 (AB)b]]

{{ColBreak}}

*[[Automated Planet Finder]]

*[[COROT]]

*[[Darwin (ESA)]]

*[[Exoplanet Archive]]

*[[Satellite Gaia]]

*[[Progetto HATNet]]

*[[HARPS]]

{{ColBreak}}

*[[PlanetQuest]]

*[[Space Interferometry Mission]]

*[[SuperWASP]]

*[[Terrestrial Planet Finder]]

*[[Trans-Atlantic Exoplanet Survey]]

{{EndMultiCol}}

==Note==

{{Reflist|colwidth=30em}}

==Collegamenti esterni==

* [http://www.nasa.gov/mission_pages/kepler/main/index.html Kepler Mission] – [[NASA]].

* [http://archive.stsci.edu/kepler/koi/search.php Kepler Mission – KOI Data Search].

* [http://archive.stsci.edu/kepler/ Kepler Mission – Public Data].

* [http://www.astronomycast.com/missions/ep-190-kepler-mission/ Kepler Mission – Audio (27:02) – Cain/Gay – Astronomy Cast (2010)].

* [http://kepler.nasa.gov/Mission/discoveries/ Kepler – Discoveries – Summary Table].

* [http://www.nasa.gov/mission_pages/kepler/news/new_planetary_system.html Kepler – Discovery of New Planetary System].

* [http://keplergo.arc.nasa.gov/ Kepler – Guest Observer Program].

* [http://astro.phys.au.dk/KASC/ Kepler – Asteroseismic Science Consortium (KASC)].

* [http://nasatech.net/Kepler090130/ Kepler – Spherical Panorama – Clean Room Before Fueling].

Cataloghi and database di [[pianeti extrasolari]]

* [http://exoplanet.eu/catalog.php "The Extrasolar Planets Encyclopaedia"] ([[Paris Observatory]])

* [http://phl.upr.edu/projects/habitable-exoplanets-catalog "The Habitable Exoplanets Catalog"] (PHL/[[University of Puerto Rico at Arecibo|UPR Arecibo]])

* [http://planetquest.jpl.nasa.gov/index.cfm "New Worlds Atlas"] ([[NASA JPL|NASA/JPL]] PlanetQuest)

{{Programma Discovery}}

{{Portale|astronautica}}

[[Categoria:Satelliti artificiali NASA]]

[[Categoria:Pianeti extrasolari]]

[[Categoria:Missioni spaziali]]

[[Categoria:Telescopi spaziali NASA]]