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'''Acrux''' ([[alpha (letter)|α]] Crucis) is a [[star]] in the [[constellation]] [[Crux]], the Southern Cross. Since the Southern Cross is roughly 60 degrees below the [[celestial equator]], Crux is only visible south of the [[Tropic of Cancer]] and therefore didn't receive an ancient proper name; "Acrux" is simply a combination of the A in Alpha plus Crux. Acrux has a [[stellar magnitude]] of 0.77, and is the twelfth brightest star in the sky. It is the southernmost first magnitude star, just beating out [[Rigil Kentaurus]] (α Centauri).
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<center>[[Image:Greifswald_in_Germany.png|Greifswald_in_Germany.png]]</center>
<center>''Map of Germany showing Greifswald''</center>
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Acrux is a [[trinary star]] located 320 light years from the solar system. Only two components are visually distinguishable, α<sup>1</sup> and α<sup>2</sup>, separated by 4 [[arcsecond]]s. α<sup>1</sup> is magnitude 1.33 and α<sup>2</sup> is magnitude 1.73, both hot [[stellar classification|class B]] (almost [[stellar classification|class O]]) stars, with surface temperatures of about 28,000 and 26,000 Kelvin respectively; their respective luminosities are 2,500 and 1,600 times that of the Sun. α<sup>1</sup> and α<sup>2</sup> orbit over such a long period that motion is only barely seen. From their minimum separation of 430 [[astronomical unit]]s, the period is at least 1500 years, and may be much longer.
'''Greifswald''' (German ''Greif''=Eagle, Wald=Forest;[[Polish language|Polish]]: ''Gryfia'') is a city in [[Mecklenburg-Western Pomerania]], [[Germany]]. Located at the south end of the Baltic Sea, and the mouth of the Ryck river. Population: ca. 55,000.
α<sup>1</sup> is itself a [[spectroscopic binary]] star, with its components thought to be around 14 and 10 times the mass of the Sun and orbiting in only 76 days at a separation of about one astronomical unit. The masses of α<sup>2</sup> and the brighter component of α<sup>1</sup> suggest that the stars will someday explode as [[supernova|supernovae]]. The fainter component of α<sup>1</sup> may survive to become a massive [[white dwarf]].
== Historical Notes ==
Another class B subgiant lies 90 arcseconds away from triple Acrux and shares Acrux's motion through space, suggesting it may be gravitationally bound to Acrux. However, if it is indeed located near Acrux, it is under-luminous for its class. It is probably just an optical [[double star]], most likely lying over twice as far away from the solar system as Acrux.
The first settlers at the place were [[Denmark|Danish]] [[Cistercians|Cistercian]] monks, who founded the Eldena monastery in [[1199]]. Due to the [[salt]] trade the monastery grew to a monumental religious centre. The town of Greifswald close to the monastery was first time mentioned in [[1248]]. After rapid growth Greifswald was one of the co-founders of the [[Hanseatic League]] at the end of the [[13th century]].
[[Category:Stars]]
The town of Greifswald was captured by [[Sweden]] in [[1631]] as a result of the 30 Years War, and remained Swedish until [[1815]].
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During the period of socialist rulership after the Second World War, parts of the historic city have seen little renovation efforts. Since the German reunification of 1989/1990 this has changed substantially.
== Ernst Moritz Arndt University ==
In 1456, the [[Ernst Moritz Arndt University of Greifswald|University of Greifswald]] (Alma Mater Gryphiswaldensis) was founded, being the second oldest in Northern [[Europe]]. For a time, it was also the oldest institution of higher education in [[Sweden]] and, later, [[Prussia]]. There are currently about 9,500 students studying at the faculties of science and math, medicine, theology, and philosophy/philology. Due to the size of the town of Greifswald, it is rather a university with a town than a town with a university. Prior to the Second World War, it was among the wealthiest universities in [[Germany]], owning lots of arable land. The university today owns several prestigious art objects, including one of four original 36 lines Gutenberg Bibles from the 15th century. In 1933, it was named after [[Ernst Moritz Arndt]].
== People ==
* Romanticist painter [[Caspar David Friedrich]] was born in Greifswald
== Weblinks ==
* [http://www.greifswald.de Official website if the City of Greifswald]
* [http://www.pommersches-landesmuseum.de Pomeranian State Museum Greifswald]
* [http://www.theater-vorpommern.de Theater Vorpommern]
* [http://www.uni-greifswald.de Ernst Moritz Arndt University of Greifswald]
''See also: [[Swedish Pomerania]]'
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