NGC 7421 | |
---|---|
Observation data (J2000 epoch) | |
Constellation | Grus |
Right ascension | 22h 56m 54.353s [1] |
Declination | −37° 20′ 50.44″ [1] |
Distance | 81.6 Mly (25.01 Mpc) [2] |
Apparent magnitude (V) | 12.0 [3] |
Characteristics | |
Type | SB(rs)bc [4] |
Mass | 20.9×109 [5] M☉ |
Apparent size (V) | 2.2′ [3] |
Other designations | |
NGC 7421, LEDA 70083, MCG -06-50-015 [6] |
NGC 7421 is a barred spiral galaxy in the southern constellation of Grus. It was discovered by English astronomer John Herschel on August 30, 1834. [7] In Danish astronomer J. L. E. Dreyer's New General Catalogue of Nebulae and Clusters of Stars it was described as: considerably bright, large, very little extended, gradually pretty much brighter middle, and partially resolved. [3] NGC 7421 is located at an estimated distance of 81.6 million light-years (25.01 Mpc ) from the Sun. [2] It is a member of the IC 1459 galaxy group. [5]
In the Third Reference Catalogue of Bright Galaxies, NGC 7421 was assigned a morphological classification of SB(rs)bc, which indicates a barred spiral galaxy (SB) with a transitional ring structure (rs) and moderately wound spiral arms (bc). [4] The galactic plane is inclined at an angle of 36.2° to the plane of the sky, with the major axis aligned along a position angle of 80.6°. It displays an asymmetric morphology, which shows up in a lopsided optical appearance and in the distribution of CO and neutral hydrogen atoms. New stars are forming at a rate of 0.274±0.041 M☉ ·yr−1. The gas fraction and star formation rate is significantly lower than normal, suggesting an interaction with the external environment. [5]
The western boundary of this galaxy resembles a bow shock that suggests an interaction with the intracluster medium. Radio mapping of neutral hydrogen by the ATCA displays an extended wake to the north and south of the galaxy, supporting this hypothesis. [8] A past tidal interaction may be needed to explain the asymmetry of this galaxy. A candidate galaxy is NGC 7418, which is located at an angular separation of ~20′. However, there are no tidal tails visible from such an encounter. [9] The total mass of the neutral hydrogen in this galaxy is 1.5×109 M☉. [8]
The type II supernova SN 2023abdg was observed in association with this galaxy. It was discovered on December 12, 2023, by ATLAS. [10]
Messier 90 is an intermediate spiral galaxy exhibiting a weak inner ring structure about 60 million light-years away in the constellation Virgo. It was discovered by Charles Messier in 1781.
Messier 99 or M99, also known as NGC 4254, is a grand design spiral galaxy in the northern constellation Coma Berenices approximately 15,000,000 parsecs from the Milky Way. It was discovered by Pierre Méchain on 17 March 1781. The discovery was then reported to Charles Messier, who included the object in the Messier Catalogue of comet-like objects. It was one of the first galaxies in which a spiral pattern was seen. This pattern was first identified by Lord Rosse in the spring of 1846.
Messier 108 is a barred spiral galaxy about 28 million light-years away from Earth in the northern constellation Ursa Major. It was discovered by Pierre Méchain in 1781 or 1782. From the Earth, this galaxy is seen almost edge-on.
NGC 2787 is a barred lenticular galaxy approximately 24 million light-years away in the northern constellation of Ursa Major. It was discovered on December 3, 1788 by German-born astronomer William Herschel. J. L. E. Dreyer described it as, "bright, pretty large, a little extended 90°, much brighter middle, mottled but not resolved, very small (faint) star involved to the southeast". The visible galaxy has an angular size of 2.5 × 1.5 arcminutes or 3.24 × 1.81 arcminutes and an apparent visual magnitude of 11.8.
NGC 4216 is a metal-rich intermediate spiral galaxy located not far from the center of the Virgo Cluster of galaxies, roughly 55 million light-years away. It is seen nearly edge-on.
NGC 2976 is a peculiar dwarf galaxy in the northern circumpolar constellation of Ursa Major. It was discovered by German-born astronomer William Herschel on November 8, 1801, and catalogued as H I.285. J. L. E. Dreyer described it as, "bright, very large, much extended 152°, star involved". It is a member of the M81 Group and lies 1° 20′ to the southwest of Messier 81. The projected separation of this galaxy from the M81 Group is 190 kpc.
NGC 5548 is a Type I Seyfert galaxy with a bright, active nucleus. This activity is caused by matter flowing onto a 65 million solar mass (M☉) supermassive black hole at the core. Morphologically, this is an unbarred lenticular galaxy with tightly-wound spiral arms, while shell and tidal tail features suggest that it has undergone a cosmologically-recent merger or interaction event. NGC 5548 is approximately 245 million light years away and appears in the constellation Boötes. The apparent visual magnitude of NGC 5548 is approximately 13.3 in the V band.
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 1566, sometimes known as the Spanish Dancer, is an intermediate spiral galaxy in the constellation Dorado, positioned about 3.5° to the south of the star Gamma Doradus. It was discovered on May 28, 1826 by Scottish astronomer James Dunlop. At 10th magnitude, it requires a telescope to view. The distance to this galaxy remains elusive, with measurements ranging from 6 Mpc up to 21 Mpc.
NGC 7424 is a barred spiral galaxy located 37.5 million light-years away in the southern constellation Grus. Its size makes it similar to our own galaxy, the Milky Way. It is called a "grand design" galaxy because of its well defined spiral arms. Two supernovae and two ultraluminous X-ray sources have been discovered in NGC 7424.
NGC 4911 is a disturbed, warped spiral galaxy with a bright prominent central starburst ring and located deep within the Coma Cluster of galaxies, which lies some 300 million light years away in the northern constellation Coma Berenices. NGC 4911 is believed to be interacting with its warped, barred lenticular companion, producing the enhanced star formation and shell-like appearance seen in optical images. The galaxy contains rich lanes of dust and gas near its centre. The existence of clouds of hydrogen within the galaxy indicates ongoing star formation. It is rare for a spiral galaxy to be situated at the heart of a cluster.
NGC 672 is a spiral galaxy in the northern constellation of Triangulum, positioned around 2° to the southwest of the star Alpha Trianguli. The original object designated NGC 672 was discovered by the German-born astronomer William Herschel on 26 October 1786, but this was later cataloged as NGC 614. The object now identified as NGC 672 was discovered by John Herschel on 11 November 1827.
NGC 4203 is the New General Catalogue identifier for a lenticular galaxy in the northern constellation of Coma Berenices. It was discovered on March 20, 1787 by English astronomer William Herschel, and is situated 5.5° to the northwest of the 4th magnitude star Gamma Comae Berenices and can be viewed with a small telescope. The morphological classification of NGC 4203 is SAB0−, indicating that it has a lenticular form with tightly wound spiral arms and a weak bar structure at the nucleus.
NGC 1614 is the New General Catalogue identifier for a spiral galaxy in the equatorial constellation of Eridanus. It was discovered on December 29, 1885 by American astronomer Lewis Swift, who described it in a shorthand notation as: pretty faint, small, round, a little brighter middle. The nebula was then catalogued by Danish-Irish astronomer J. L. E. Drayer in 1888. When direct photography became available, it was noted that this galaxy displayed some conspicuous peculiarities. American astronomer Halton Arp included it in his 1966 Atlas of Peculiar Galaxies. In 1971, Swiss astronomer Fritz Zwicky described it as a "blue post-eruptive galaxy, compact patchy core, spiral plumes, long blue jet SSW".
NGC 1792 is a spiral galaxy located in the southern Columba constellation. It was discovered by Scottish astronomer James Dunlop on October 4, 1826. This galaxy is located at a distance of about 36.4 million light-years and is receding from the Milky Way with a heliocentric radial velocity of 1,208 km/s. NGC 1792 is a member of the NGC 1808 cluster of galaxies.
NGC 2865 is an isolated elliptical galaxy in the equatorial constellation of Hydra. The core region of the galaxy shows a kinematically distinct component showing indications of a recent accretion or merger event that led to a burst of star formation around the nucleus. Observational constraints require this to have occurred within the last 100–400 million years, with the merger most likely being an Sb or Sc-class spiral galaxy.
NGC 7418 is an intermediate spiral galaxy located in the constellation Grus. It is located at a distance of circa 60 million light-years from Earth, which, given its apparent dimensions, means that NGC 7418 is about 60,000 light-years across. It was discovered by John Herschel on August 30, 1834.
NGC 4302 is an edge-on spiral galaxy located about 55 million light-years away in the constellation Coma Berenices. It was discovered by astronomer William Herschel on April 8, 1784 and is a member of the Virgo Cluster.
NGC 3175 is a spiral galaxy located in the far eastern part of the southern constellation of Antlia at an approximate distance of 54 million light-years. NGC 3175 was discovered on March 30, 1835 by English astronomer John Herschel, whose notes described it as, "considerably bright, large, much extended NE-SW, very gradually little brighter middle". This galaxy is the namesake of the NGC 3175 group of galaxies, which includes the spiral galaxy NGC 3137.
NGC 3044 is a barred spiral galaxy in the equatorial constellation of Sextans. It was discovered on December 13, 1784, by German-born English astronomer William Herschel. In 1888, Danish astronomer J. L. E. Dreyer described it as "very faint, very large, very much extended 122°". It is located at an estimated distance of 67 million light years. In the B band of the UBV photometric system, the galaxy spans 4.70′ by 0.80′ with the major axis aligned along a position angle of 113°. It is a relatively isolated galaxy with no nearby companions. R. B. Tully in 1988 assigned it as a member of the widely displaced Leo Cloud.