Editing Galaxy (section)

==== Quasar ====
{{Main|Quasar}}

Quasars are the most energetic and distant members of active galactic nuclei. Extremely luminous, they were first identified as high redshift sources of electromagnetic energy, including radio waves and visible light, that appeared more similar to stars than to extended sources similar to galaxies. Their luminosity can be 100 times that of the Milky Way.{{sfn|Fraknoi et al.|2023|pp=[https://openstax.org/books/astronomy-2e/pages/27-1-quasars 899–906]}} The nearest known quasar, [[Markarian 231]], is about 581 million light-years from Earth,<ref>{{Cite journal |last1=Kovačević |first1=Andjelka B |last2=Yi |first2=Tignfeng |last3=Dai |first3=Xinyu |last4=Yang |first4=Xing |last5=Čvorović-Hajdinjak |first5=Iva |last6=Popović |first6=Luka Č |date=2020-05-21 |title=Confirmed short periodic variability of subparsec supermassive binary black hole candidate Mrk 231 |url=https://academic.oup.com/mnras/article/494/3/4069/5809369 |journal=[[Monthly Notices of the Royal Astronomical Society]] |language=en |volume=494 |issue=3 |pages=4069–4076 |doi=10.1093/mnras/staa737 |doi-access=free |issn=0035-8711|arxiv=2003.06359 }}</ref> while others have been discovered as far away as [[UHZ1]], roughly 13.2 billion light-years distant.<ref>{{Cite web |date=2023-11-10 |title=UHZ1: Distant Galaxy and Black Hole |url=https://apod.nasa.gov/apod/ap231110.html |access-date=2024-02-18 |editor-last1=Nemiroff|editor-first1=Robert|editor-last2=Bonnell|editor-first2=Jerry|website=[[Astronomy Picture of the Day]]|publisher=[[NASA]], [[Michigan Technological University]]}}</ref><ref>{{Cite journal |last1=Bogdán |first1=Ákos |last2=Goulding |first2=Andy D. |last3=Natarajan |first3=Priyamvada |last4=Kovács |first4=Orsolya E. |last5=Tremblay |first5=Grant R. |last6=Chadayammuri |first6=Urmila |last7=Volonteri |first7=Marta |author7-link=Marta Volonteri|last8=Kraft |first8=Ralph P. |last9=Forman |first9=William R. |last10=Jones |first10=Christine |last11=Churazov |first11=Eugene |last12=Zhuravleva |first12=Irina |date=January 2024 |title=Evidence for heavy-seed origin of early supermassive black holes from a z ≈ 10 X-ray quasar |url=https://www.nature.com/articles/s41550-023-02111-9 |journal=[[Nature Astronomy]] |language=en |volume=8 |issue=1 |pages=126–133 |arxiv=2305.15458 |bibcode=2024NatAs...8..126B |doi=10.1038/s41550-023-02111-9 |s2cid=258887541 |issn=2397-3366}}</ref> Quasars are noteworthy for providing the first demonstration of the phenomenon that [[Gravitational lens|gravity can act as a lens for light]].<ref>{{Cite journal |last1=Blandford |first1=R. D. |last2=Narayan |first2=R. |date=September 1992 |title=Cosmological Applications of Gravitational Lensing |url=https://www.annualreviews.org/doi/10.1146/annurev.aa.30.090192.001523 |journal=[[Annual Review of Astronomy and Astrophysics]] |language=en |volume=30 |issue=1 |pages=311–358 |doi=10.1146/annurev.aa.30.090192.001523 |issn=0066-4146}}</ref>