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Dwarf galaxies around the [[Milky Way]] and [[Andromeda Galaxy|Andromeda]] galaxies are observed to be orbiting in thin, planar structures whereas the simulations predict that they should be distributed randomly about their parent galaxies.<ref name=Pawlowski>{{cite journal |first1=Marcel |last1=Pawlowski |display-authors=etal |title=Co-orbiting satellite galaxy structures are still in conflict with the distribution of primordial dwarf galaxies |journal=Monthly Notices of the Royal Astronomical Society |volume=442 |issue=3 |pages=2362–2380 |year=2014 |arxiv=1406.1799|doi=10.1093/mnras/stu1005 |doi-access=free |bibcode=2014MNRAS.442.2362P }}</ref> However, latest research suggests this seemingly bizarre alignment is just a quirk which will dissolve over time.<ref name="Sawala">{{cite journal |first1=Till |last1=Sawala |first2=Marius |last2=Cautun |first3=Carlos |last3=Frenk |display-authors=etal |title=The Milky Way's plane of satellites: consistent with ΛCDM|journal=Nature Astronomy |year=2022 |volume=7 |issue=4 |pages=481–491 |arxiv=2205.02860|doi=10.1038/s41550-022-01856-z |bibcode=2023NatAs...7..481S|s2cid=254920916 }}</ref>
There has been debate on whether early massive galaxies and supermassive black holes are in conflict with LCDM<ref>{{Cite journal |last1=Steinhardt |first1=Charles. L. |last2=Capak |first2=Peter |last3=Masters |first3=Dan |last4=Speagle |first4=Josh S. |date=2016-06-10 |title=The Impossibly Early Galaxy Problem |journal=The Astrophysical Journal |volume=824 |issue=1 |pages=21 |doi=10.3847/0004-637X/824/1/21 |arxiv=1506.01377 |bibcode=2016ApJ...824...21S |doi-access=free |issn=0004-637X}}</ref>. To make such a comparison, one must model the complex physics of galaxy formation, as well as the underlying LCDM cosmology.<ref>{{Cite journal |last1=Behroozi |first1=Peter |last2=Silk |first2=Joseph |date=2018-07-11 |title=The most massive galaxies and black holes allowed by ΛCDM |url=https://academic.oup.com/mnras/article/477/4/5382/4975781 |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=477 |issue=4 |pages=5382–5387 |doi=10.1093/mnras/sty945 |doi-access=free |issn=0035-8711}}</ref> Tests using galaxies are therefore less direct, as they require assumptions about how galaxies form.
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