The M81 Group is a galaxy group in the constellations Ursa Major and Camelopardalis that includes the galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses. The approximate center of the group is located at a distance of 3.6 Mpc, making it one of the nearest groups to the Local Group. The group is estimated to have a total mass of ×1012M☉. The M81 Group, the Local Group, and other nearby groups all lie within the Virgo Supercluster.
The Triangulum Galaxy is a spiral galaxy 2.73 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC (New General Catalogue) 598. With the D25 isophotal diameter of 18.74 kiloparsecs (61,100 light-years), the Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Andromeda Galaxy and the Milky Way.
The Pinwheel Galaxy is a face-on spiral galaxy 21 million light-years away from Earth in the constellation Ursa Major. It was discovered by Pierre Méchain in 1781 and was communicated that year to Charles Messier, who verified its position for inclusion in the Messier Catalogue as one of its final entries.
Messier 83 or M83, also known as the Southern Pinwheel Galaxy and NGC 5236, is a barred spiral galaxy approximately 15 million light-years away in the constellation borders of Hydra and Centaurus. Nicolas-Louis de Lacaille discovered M83 on 23 February 1752 at the Cape of Good Hope. Charles Messier added it to his catalogue of nebulous objects in March 1781.
The Whirlpool Galaxy, also known as Messier 51a (M51a) or NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus. It lies in the constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy. It is about 31 million light-years (9.5 Mpc) away from Earth and 76,900 ly (23,580 pc) in diameter.
NGC 5866 is a relatively bright lenticular galaxy in the constellation Draco. NGC 5866 was most likely discovered by Pierre Méchain or Charles Messier in 1781, and independently found by William Herschel in 1788. Measured orbital velocities of its globular cluster system imply that dark matter makes up only 34±45% of the mass within 5 effective radii, a notable paucity.
Messier 102 is a galaxy listed in the Messier Catalogue that cannot be unambiguously identified. Its original discoverer Pierre Méchain retracted his discovery two years after publication and said that it was a duplicate observation of Messier 101. Later historical evidence favors that M102 is actually the galaxy NGC 5866, although other galaxies have been suggested as possible identities. The National Aeronautics and Space Administration (NASA) considers it to be the same as NGC 5866.
Messier 49 is a giant elliptical galaxy about 56 million light-years away in the equatorial constellation of Virgo. This galaxy was discovered by astronomer Charles Messier in 1777.
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 109 is a barred spiral galaxy exhibiting a weak inner ring structure around the central bar approximately 67.2 ± 23 million light-years away in the northern constellation Ursa Major. M109 can be seen south-east of the star Phecda.
The M101 Group is a loose group of galaxies located in the constellation Ursa Major. The group is named after the brightest galaxy in the group, the Pinwheel Galaxy (M101). Most of the other members of the group are companions of the Pinwheel Galaxy. The group itself is one of many located within the Virgo Supercluster.
NGC 891 is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6, 1784. The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster. It has an H II nucleus.
The Atlas of Peculiar Galaxies is a catalog of peculiar galaxies produced by Halton Arp in 1966. A total of 338 galaxies are presented in the atlas, which was originally published in 1966 by the California Institute of Technology. The primary goal of the catalog was to present photographs of examples of the different kinds of peculiar structures found among galaxies.
David Dunlap Observatory Catalogue, known as the DDO or A Catalogue of Dwarf Galaxies, is a catalogue of dwarf galaxies that was compiled by Sidney van den Bergh and published by the David Dunlap Observatory in 1959.
NGC 5474 is a peculiar dwarf galaxy in the constellation Ursa Major. It is one of several companion galaxies of the Pinwheel Galaxy (M101), a grand-design spiral galaxy. Among the Pinwheel Galaxy's companions, this galaxy is the closest to the Pinwheel Galaxy itself. The gravitational interaction between NGC 5474 and the Pinwheel Galaxy has strongly distorted the former. As a result, the disk is offset relative to the nucleus. The star formation in this galaxy is also offset from the nucleus. NGC 5474 shows some signs of a spiral structure. As a result, this galaxy is often classified as a dwarf spiral galaxy, a relatively rare group of dwarf galaxies.
The NGC 5866 Group is a small group of galaxies located in the constellation Draco. The group is named after NGC 5866, the galaxy with the highest apparent magnitude in the group, although some galaxy group catalogs list NGC 5907 as the brightest member.
The M51 Group is a group of galaxies located in Canes Venatici. The group is named after the brightest galaxy in the group, the Whirlpool Galaxy (M51A). Other notable members include the companion galaxy to the Whirlpool Galaxy (M51B) and the Sunflower Galaxy (M63).
NGC 936 is a barred lenticular galaxy in the constellation Cetus. It is at a distance of about 60 million light-years away from Earth. Its nucleus and prominent bar have high surface brightness. Because of the shape of the prominent bar, the nucleus and the ring of stars at the end of the barrel, the galaxy has been compared with the shape of a TIE fighter, from the Star Wars universe, and thus NGC 936 has been named Darth Vader’s Galaxy or Darth Vader’s Starfighter. By measuring the radial velocity of the disc, Kormendy found in 1986 that the disc is stable, which is the reason why it is so smooth.
NGC 765 is an intermediate spiral galaxy located in the constellation Aries. It is located at a distance of circa 220 million light years from Earth, which, given its apparent dimensions, means that NGC 765 is about 195,000 light years across. It was discovered by Albert Marth on October 8, 1864. The galaxy has an extensive hydrogen (HI) disk with low surface brightness, whose diameter is estimated to be 240 kpc.
UGC 9405 is a faint dwarf irregular galaxy situated in the constellation of Ursa Major. It is about 20.5 million light-years, or 6.3 megaparsecs, away from the Earth. It is listed as a member of the M101 Group, a group containing the several galaxies orbiting the largest, Pinwheel Galaxy (M101). However, due to its far distance from the Pinwheel Galaxy, its membership of the group is uncertain.
