| 词条 | NGC 6240 |
| 释义 |
| name = NGC 6240 | image = Hubble revisits tangled NGC 6240.jpg | image_size = 300px | caption = At the centre of NGC 6240 there are two supermassive black holes spiraling closer and closer to one another.[1] | epoch = J2000 | type = I0 pec[2] | ra = {{RA|16|52|58.9}}[2] | dec = {{DEC|+02|24|03}}[2] | dist_ly = 400 Mly | z = 7339 ± 9 km/s[2] | appmag_v = 12.8[2] | size_v = 2′.1 × 1′.1[2] | constellation name = Ophiuchus | notes = merger remnant | names = IC 4625,[2] UGC 10592,[2] PGC 59186,[2] VV 617[2] }}NGC 6240 is a nearby ultraluminous infrared galaxy (ULIRG) in the constellation Ophiuchus. The galaxy is the remnant of a merger between two smaller galaxies. The collision between the two progenitors has resulted in a single larger galaxy with two distinct nuclei and a highly disturbed structure, including faint extensions and loops.[3] Double nucleiStar formation versus supermassive black holesThe power sources of ULIRGs in general has been greatly debated. Infrared light from galaxies generally originates from dust in the interstellar medium. ULIRGs are abnormally bright in the infrared. The infrared dust emission in ULIRGs is over one trillion times more luminous than the Sun (i.e. it has an infrared luminosity of {{Solar luminosity|1012}}). Astronomers have speculated that either intense star formation regions or active galactic nuclei (which contain supermassive black holes) may be responsible for the intense dust heating that produces this emission, although the general consensus is that both may be present in most ULIRGs. Studying the exact nature of ULIRGs has been difficult, however, because the dust in the centers of these galaxies obscures both visible and near-infrared starlight and because theoretical models of both starbursts and active galactic nuclei have demonstrated that they may look similar. Because NGC 6240 is a nearby example of such a ULIRG, astronomers have studied it intensively to understand its power source. X-Ray ObservationsObservations performed by Stefanie Komossa and collaborators with the Chandra X-Ray Observatory have detected strong hard X-ray emission from both of the nuclei. The intensity of this emission and the presence of emission from lowly ionized or neutral iron indicate that both of the nuclei are active galactic nuclei.[4] Presumably, these are the black holes that were originally at the centers of the two merging galaxies. Over the course of millions of years, the two black holes are expected to come closer together and form a binary supermassive black hole. {{clear}}Final StagesA galaxy merger is a slow process lasting more than a billion years as two galaxies, under the inexorable pull of gravity, dance toward each other before finally joining together. After research done over the past few years, scientists have concluded that this galaxy has reached its last stages before colliding into on another. Photographic evidence proves that the two nuclei have been growing closer, and in that process, they have been emitting more gasses and stellar winds outward.Those winds evict about 100 solar masses in gases from the galaxy every year. These type of winds and growth of the black holes are known to occur during the last 10 to 20 million years of the merger; it is assumed that this is the amount of time left for this galaxy. [5] GallerySee also{{commons|NGC 6240}}
References1. ^{{cite web|title=Hubble revisits tangled NGC 6240|url=http://www.spacetelescope.org/images/potw1520a/|accessdate=12 June 2015}} 2. ^1 2 3 4 5 6 7 8 9 {{cite web | title=NASA/IPAC Extragalactic Database | work=Results for NGC 6240 | url=http://nedwww.ipac.caltech.edu/ | accessdate=2006-08-16}} 3. ^{{cite journal | author=J. W. Fried | author2=H. Schulz | title=NGC 6240 - A unique interacting galaxy | journal=Astronomy and Astrophysics | date=1983 | volume=118 | pages=166–170 | bibcode=1983A&A...118..166F}} 4. ^{{cite journal | author=S. Komossa | display-authors=4 | author2=V. Burwitz | author3=G. Hasinger | author4=P.Predehl | author5=J. S. Kaastra | author6=Y. Ikebe | title=Discovery of a Binary Active Galactic Nucleus in the Ultraluminous Infrared Galaxy NGC 6240 Using Chandra | journal=Astrophysical Journal | date=2003 | volume=582 | issue=1 | pages=L15–L19 | bibcode=2003ApJ...582L..15K | doi=10.1086/346145|arxiv = astro-ph/0212099 }} 5. ^{{Cite news|url=https://www.nasa.gov/feature/goddard/2018/astronomers-unveil-growing-black-holes-in-colliding-galaxies|title=Astronomers Unveil Growing Black Holes in Colliding Galaxies|last=Hille|first=Karl|date=2018-11-07|work=NASA|access-date=2018-11-26|language=en}} 6. ^{{cite web |title=Hubble and Keck observatories uncover black holes coalescing |url=https://www.spacetelescope.org/images/opo1828a/ |website=www.spacetelescope.org |accessdate=8 November 2018}} External links
9 : Irregular galaxies|Interacting galaxies|Peculiar galaxies|Luminous infrared galaxies|Ophiuchus (constellation)|NGC objects|IC objects|UGC objects|Principal Galaxies Catalogue objects |
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