M82 X-2

{{short description|X-ray pulsar located in the galaxy Messier 82}}

{{Use dmy dates|date=October 2014}}

{{Starbox begin

| name = M82 X-2

}}

{{Starbox image

| image = 200px

| caption = M82 X-2 glows pink in the X-ray spectrum at the center of Messier 82. M82 X-1 is to its right.{{sfn|Smith et al.|1995|p=204}}

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{{Starbox observe

| epoch = J2000.0

| constell = Ursa Major

| ra = {{RA|09|55|51.0}}

| dec = {{DEC|69|40|45}}

| appmag_v =

}}

{{Starbox astrometry

| dist_ly = 12 million

| dist_pc = 3.5 million

}}

{{Starbox catalog

| names = CXOU J095550.9+694044, {{nowrap|NuSTAR J095551+6940.8}}

}}

{{Starbox reference

| Simbad = CXOU+J095550.9%2B694044

}}

{{Starbox end}}

M82 X-2 is an X-ray pulsar located in the galaxy Messier 82, approximately 12 million light-years from Earth. It is exceptionally luminous, radiating energy equivalent to approximately ten million Suns. This object is part of a binary system: If the pulsar is of an average size, {{solar mass|1.4|link=yes}}, then its companion is at least {{solar mass|5.2|link=yes}}. On average, the pulsar rotates every 1.37 seconds, and revolves around its more massive companion every 2.5 days.{{sfn|Smith et al.|1995|p=202}}

M82 X-2 is an ultraluminous X-ray source (ULX), shining about 100 times brighter than theory suggests something of its mass should be able to. Its brightness is many times higher than the Eddington limit, a basic physics guideline that sets an upper limit on the brightness that an object of a given mass should be able to achieve. Possible explanations for violations of the Eddington limit include geometrical effects arising from the funneling of in-falling material along magnetic field lines.

While M82 X-2 was previously known as an X-ray source, it was not until an observation campaign to study the newly discovered supernova SN 2014J in January 2014 that X-2's true nature was uncovered. Scientists looking at data from the NuSTAR spacecraft noticed a pulsing in the X-ray spectrum coming from near the supernova in Messier 82. Data from the Chandra and Swift spacecraft was used to verify the NuSTAR findings and provide the necessary spatial resolution to determine the exact source.{{sfn|Smith et al.|1995|p=202}} After combining the NuSTAR and Chandra data, scientists were able to discern that M82 X-2 emitted both an X-ray beam and continuous broad X-ray radiation.{{sfn|Smith et al.|1995|p=204}} LXs). In 2023 new NuSTAR data confirmed that it exceeded the Eddington limit.{{Cite journal |last1=Bachetti |first1=Matteo |last2=Heida |first2=Marianne |last3=Maccarone |first3=Thomas |last4=Huppenkothen |first4=Daniela |last5=Israel |first5=Gian Luca |last6=Barret |first6=Didier |last7=Brightman |first7=Murray |last8=Brumback |first8=McKinley |last9=Earnshaw |first9=Hannah P. |last10=Forster |first10=Karl |last11=Fürst |first11=Felix |last12=Grefenstette |first12=Brian W. |last13=Harrison |first13=Fiona A. |last14=Jaodand |first14=Amruta D. |last15=Madsen |first15=Kristin K. |date=2022-10-01 |title=Orbital Decay in M82 X-2 |journal=The Astrophysical Journal |volume=937 |issue=2 |pages=125 |doi=10.3847/1538-4357/ac8d67 |arxiv=2112.00339 |bibcode=2022ApJ...937..125B |issn=0004-637X|hdl=2299/25784 |hdl-access=free |doi-access=free }}{{Cite web |last= |title=NASA Study Helps Explain Limit-Breaking Ultra-Luminous X-Ray Sources |url=https://www.jpl.nasa.gov/news/nasa-study-helps-explain-limit-breaking-ultra-luminous-x-ray-sources |access-date=2023-04-18 |website=NASA Jet Propulsion Laboratory (JPL) |language=en-US}}