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NGC 6240 | |
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![]() At the centre of NGC 6240 there are three supermassive black holes spiraling closer and closer to one another. [1] | |
Observation data (J2000 epoch) | |
Constellation | Ophiuchus |
Right ascension | 16h 52m 58.9s [2] |
Declination | +02° 24′ 03″ [2] |
Redshift | 7339 ± 9 km/s [2] |
Distance | 400 Mly |
Apparent magnitude (V) | 12.8 [2] |
Characteristics | |
Type | I0 pec [2] |
Apparent size (V) | 2.1′ × 1.1′ [2] |
Notable features | merger remnant |
Other designations | |
IC 4625, [2] UGC 10592, [2] PGC 59186, [2] VV 617 [2] |
NGC 6240, also known as the Starfish Galaxy, is a nearby ultraluminous infrared galaxy (ULIRG) in the constellation Ophiuchus. The galaxy is the remnant of a merger between three smaller galaxies. The collision between the three progenitor galaxies has resulted in a single, larger galaxy with three distinct nuclei and a highly disturbed structure, including faint extensions and loops. [3]
The 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 1012 L☉). 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.[ citation needed ]
Observations 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.[ citation needed ]
Recent studies by Wolfram Kollatschny and collaborators using the MUSE instrument on board the VLT have revealed that there are in fact three, not two, supermassive black holes at the core of this remnant. Their masses are suggested to be 90, 710 and 360 million solar masses. [5] Two of the three black holes are active. The additional SMBH implies that three original galaxies are merging instead of two.
Four supernovae have been observed in NGC 6240: SN 2000bg (Type IIn, mag. 17.4), [6] SN 2010gp (type Ia, mag. 17.5), [7] SN 2013dc (Type IIP, mag. 18.7), [8] and PSN J16525760+0223367 (type Ia, mag. 15.8). [9]
A 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 one 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 the galaxy to finish its collision phase. [10] After this phase, the merged galaxies will become one, becoming a post-merger object until if and when any tidal tails and plumes evaporate.
Seyfert galaxies are one of the two largest groups of active galaxies, along with quasar host galaxies. They have quasar-like nuclei with very high surface brightnesses whose spectra reveal strong, high-ionisation emission lines, but unlike quasars, their host galaxies are clearly detectable.
A starburst galaxy is one undergoing an exceptionally high rate of star formation, as compared to the long-term average rate of star formation in the galaxy, or the star formation rate observed in most other galaxies.
NGC 1097 is a barred spiral galaxy about 45 million light years away in the constellation Fornax. It was discovered by William Herschel on 9 October 1790. It is a severely interacting galaxy with obvious tidal debris and distortions caused by interaction with the companion galaxy NGC 1097A.
NGC 3227 is an intermediate spiral galaxy that is interacting with the dwarf elliptical galaxy NGC 3226. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the Atlas of Peculiar Galaxies. Both galaxies may be found in the constellation Leo. It is a member of the NGC 3227 Group of galaxies, which is a member of the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster.
Luminous infrared galaxies or LIRGs are galaxies with luminosities, the measurement of brightness, above 1011 L☉. They are also referred to as submillimeter galaxies (SMGs) through their normal method of detection. LIRGs are more abundant than starburst galaxies, Seyfert galaxies and quasi-stellar objects at comparable luminosity. Infrared galaxies emit more energy in the infrared than at all other wavelengths combined. A LIRG's luminosity is 100 billion times that of the Sun.
Arp 220 is the result of a collision between two galaxies which are now in the process of merging. It is the 220th object in Halton Arp's Atlas of Peculiar Galaxies.
NGC 5033 is an inclined spiral galaxy located in the constellation Canes Venatici. Distance estimates vary from between 38 and 60 million light years from the Milky Way. The galaxy has a very bright nucleus and a relatively faint disk. Significant warping is visible in the southern half of the disk. The galaxy's relatively large angular size and relatively high surface brightness make it an object that can be viewed and imaged by amateur astronomers. The galaxy's location relatively near Earth and its active galactic nucleus make it a commonly studied object for professional astronomers.
NGC 5005, also known as Caldwell 29, is an inclined spiral galaxy in the constellation Canes Venatici. The galaxy has a relatively bright nucleus and a bright disk that contains multiple dust lanes. The galaxy's high surface brightness makes it an object that is visible to amateur astronomers using large amateur telescopes.
NGC 1672 is a barred spiral galaxy located in the constellation Dorado. It was discovered by the astronomer James Dunlop on November 5, 1826. It was originally unclear whether it was a member of the Dorado Group, with some sources finding it to be a member and other sources rejecting its membership. However, recent tip of the red-giant branch (TRGB) measurements indicate that NGC 1672 is located at the same distance as other members, suggesting it is indeed a member of the Dorado Group.
NGC 5643 is an intermediate spiral galaxy in the constellation Lupus. Based on the tip of the red-giant branch distance indicator, it is located at a distance of about 40 million light-years. NGC 5643 has an active galactic nucleus and is a type II Seyfert galaxy.
NGC 2782 is a peculiar spiral galaxy that formed after a galaxy merger in the constellation Lynx. The galaxy lies 75 million light years away from Earth, which means, given its apparent dimensions, that NGC 2782 is approximately 100,000 light years across. NGC 2782 has an active galactic nucleus and it is a starburst and a type 1 Seyfert galaxy. NGC 2782 is mentioned in the Atlas of Peculiar Galaxies in the category galaxies with adjacent loops.
NGC 4424 is a spiral galaxy located in the equatorial constellation of Virgo. It was discovered February 27, 1865 by German astronomer Heinrich Louis d'Arrest. This galaxy is located at a distance of 13.5 million light years and is receding with a heliocentric radial velocity of 442 km/s. It has a morphological class of SB(s)a, which normally indicates a spiral galaxy with a barred structure (SB), no inner ring feature (s), and tightly-wound spiral arms (a). The galactic plane is inclined at an angle of 62° to the line of sight from the Earth. It is a likely member of the Virgo Cluster of galaxies.
NGC 3256 is a peculiar galaxy formed from the collision of two separate galaxies in the constellation of Vela. NGC 3256 is located about 100 million light-years away and belongs to the Hydra–Centaurus Supercluster complex. NGC 3256 provides a nearby template for studying the properties of young star clusters in tidal tails. The system hides a double nucleus and a tangle of dust lanes in the central region. The telltale signs of the collision are two extended luminous tails swirling out from the galaxy. The tails are studded with a particularly high density of star clusters. NGC 3256 is the most luminous galaxy in the infrared spectrum located within z 0.01 from Earth.
NGC 7469 is an intermediate spiral galaxy in the constellation of Pegasus. NGC 7469 is located about 200 million light-years away from Earth, which means, given its apparent dimensions, that NGC 7469 is approximately 90,000 light-years across. It was discovered by William Herschel on November 12, 1784.
NGC 7674 is a spiral galaxy located in the constellation Pegasus. It is located at a distance of about 350 million light years from Earth, which, given its apparent dimensions, means that NGC 7674 is about 125,000 light years across. It was discovered by John Herschel on August 16, 1830.
NGC 985 is a ring galaxy in the constellation of Cetus. It is located about 550 million light years away from Earth, which means, given its apparent dimensions, that NGC 985 is approximately 160,000 light years across. It was discovered by Francis Leavenworth in 1886. It is a type 1 Seyfert galaxy.
NGC 6951 is a barred spiral galaxy located in the constellation Cepheus. It is located at a distance of about 75 million light-years from Earth, which, given its apparent dimensions, means that NGC 6951 is about 100,000 light-years across. It was discovered by Jérôme Eugène Coggia in 1877 and independently by Lewis Swift in 1878.
NGC 3393 is a barred spiral galaxy located in the constellation Hydra. It is located at a distance of circa 180 million light-years from Earth, which, given its apparent dimensions, means that NGC 3393 is about 140,000 light-years across. It was discovered by John Herschel on March 24, 1835. It is a Type II Seyfert galaxy, known to host two supermassive black holes, which are the nearest known pair of supermassive black holes to Earth.
Markarian 273 is a galaxy merger located in the constellation Ursa Major. It is located at a distance of about 500 million light years from Earth, which, given its apparent dimensions, means that Markarian 273 is about 130,000 light years across. It is an ultraluminous infrared galaxy and a Seyfert galaxy.
NGC 7682 is a barred spiral galaxy in the constellation Pisces. It is located at a distance of about 180 million light years from Earth, which, given its apparent dimensions, means that NGC 7682 is about 65,000 light years across. It was discovered by Heinrich d'Arrest on September 23, 1864.