| NGC 7727 | |
|---|---|
 NGC 7727 by HST | |
| Observation data (J2000 epoch) | |
| Constellation | Aquarius |
| Right ascension | 23h 39.9m [1] |
| Declination | −12° 17′ 34″ [1] |
| Apparent magnitude (V) | 11.5 [1] |
| Characteristics | |
| Type | SAB(s)a pec [1] |
| Apparent size (V) | 4.7′ × 3.5′ [1] |
| Other designations | |
| PGC 72060, Arp 222 | |
NGC 7727 is a peculiar galaxy in the constellation Aquarius. It harbors two galactic nuclei, each containing a supermassive black hole, separated 1,600 light years apart. [2]
This object is located at a distance of 23.3 megaparsecs (76 million light years) from the Milky Way [1] and has a peculiar aspect, with several plumes and streams of irregular shape that explains its inclusion on Halton C. Arp's Atlas of Peculiar Galaxies with the number 222, being classified as a "Galaxy with amorphous spiral arms".
In all likelihood, this system is the product of the merger of two previous spiral galaxies that took place 1 billion years ago, [3] with the aforementioned stellar plumes and streams being the remnants of the disks of the two galaxies that collided to form this object.
Two starlike objects can be seen in NGC 7727's center, at least one of them likely being the former core of one of those two spiral galaxies. [4] In addition to this, 23 objects – candidates to be young globular clusters formed in the collision – can be found in this system. [3]
NGC 7727 is very similar to NGC 7252, another galaxy product of the collision and merging of two former spiral galaxies, in the same constellation. However it has far less gas (neutral hydrogen and molecular hydrogen) than the latter. [5]
NGC 7727's most likely fate is to become an elliptical galaxy in the future, with very little interstellar dust and star formation. [6]
In November 2021, scientists announced the discovery of a pair of supermassive black holes in NGC 7727, detected with the Very Large Telescope's multi-unit spectroscopic explorer (MUSE) at the European Southern Observatory. The black holes have masses of 154 and 6.3 million solar masses, and are separated 1,600 light years apart. The pair are among the closest confirmed supermassive black holes to Earth at about 89 million light years away. Although the pair are separated closely enough to gravitationally influence each other, the smaller black hole is not bound in orbit around the larger black hole due to the surrounding mass of the NGC 7727 core region. The black holes will eventually merge in the next 250 million years, producing powerful, low-frequency gravitational waves in the process. [7] [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.
A supermassive black hole is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (M☉). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, not even light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way galaxy has a supermassive black hole at its center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars.
NGC 5195 is a dwarf galaxy that is interacting with the Whirlpool Galaxy. Both galaxies are located approximately 25 million light-years away in the constellation Canes Venatici. Together, the two galaxies are one of the most famous interacting galaxy pairs.
Interacting galaxies are galaxies whose gravitational fields result in a disturbance of one another. An example of a minor interaction is a satellite galaxy disturbing the primary galaxy's spiral arms. An example of a major interaction is a galactic collision, which may lead to a galaxy merger.
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.
NGC 4945 (also known as Caldwell 83) is a barred spiral galaxy in the constellation Centaurus, visible near the star Xi Centauri. The galaxy was discovered by James Dunlop in 1826 and is thought to be similar to the Milky Way Galaxy, although X-ray observations show that NGC 4945 has an unusual energetic Seyfert 2 nucleus that might house a supermassive black hole. Around the nucleus of the galaxy, there is a dense disk of dust and gas, along with many dense star clusters. This object has an estimated mass of 1.4+1.4
−0.7×1011 M☉.
The Eyes Galaxies are a pair of galaxies about 52 million light-years away in the constellation Virgo. The pair are members of the string of galaxies known as Markarian's Chain.
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 7252 is a peculiar galaxy resulting from an interaction between two galaxies that started a billion years ago. It is located 220 million light years away in the constellation Aquarius. It is also called Atoms for Peace Galaxy, a nickname which comes from its loop-like structure, made of stars, that resembles a diagram of an electron orbiting an atomic nucleus.
NGC 7314 is a spiral galaxy located in the southern constellation of Piscis Austrinus. It was discovered by English astronomer John Herschel on July 29, 1834. This is a nearby Seyfert (active) galaxy, located at a distance of approximately 54.6 megalight-years from the Milky Way. Since it appears to have detached spiral arm segments, it was listed in Halton Arp's Atlas of Peculiar Galaxies.
NGC 2276 is an intermediate spiral galaxy in the constellation Cepheus. The galaxy lies 120 million light-years away from Earth. NGC 2276 has an asymmetrical appearance, most likely caused by gravitational interactions with its neighbor, elliptical galaxy NGC 2300. One of the many starburst spiral arms contains an intermediate mass black hole with 50,000 times the mass of the Sun, named NGC 2276-3c. NGC 2276-3c has produced two jets: a large-scale radio jet, approximately 2,000 light years long, and an "inner jet" about 6 light years long. The galaxy shows an enhanced rate of star formation that may have been triggered by a collision with a dwarf galaxy, or by the gravitational interaction with its neighbor compressing gas and dust.
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 3642 is a spiral galaxy in the constellation Ursa Major. The galaxy has a low-ionization nuclear emission-line region. It is located at a distance of circa 30 million light years from Earth, which, given its apparent dimensions, means that NGC 3642 is about 50,000 light years across. The galaxy is characterised by an outer pseudoring, which was probably formed after the accretion of a gas rich dwarf galaxy.
NGC 4660 is an elliptical galaxy located about 63 million light-years away in the constellation Virgo. The galaxy was discovered by astronomer William Herschel on March 15, 1784 and is a member of the Virgo Cluster.
NGC 2936 is an interacting spiral galaxy located at a distance of 326 million light years, in the constellation Hydra. NGC 2936 is interacting with elliptical galaxy NGC 2937, located just beneath it. They were both discovered by Albert Marth on Mar 3, 1864. To some astronomers, the galaxy looks like a penguin or a porpoise. NGC 2936, NGC 2937, and PGC 1237172 are included in the Atlas of Peculiar Galaxies as Arp 142 in the category "Galaxy triplet".
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 541 is a lenticular galaxy located in the constellation Cetus. It is located at a distance of circa 230 million light years from Earth, which, given its apparent dimensions, means that NGC 541 is about 130,000 light years across. It was discovered by Heinrich d'Arrest on October 30, 1864. It is a member of the Abell 194 galaxy cluster and is included in the Atlas of Peculiar Galaxies in the category galaxies with nearby fragments. NGC 541 is a radio galaxy of Fanaroff–Riley class I, also known as 3C 40A.
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.
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