Centaurus is a bright constellation in the southern sky. One of the largest constellations, Centaurus was included among the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. In Greek mythology, Centaurus represents a centaur; a creature that is half human, half horse. Notable stars include Alpha Centauri, the nearest star system to the Solar System, its neighbour in the sky Beta Centauri, and V766 Centauri, one of the largest stars yet discovered. The constellation also contains Omega Centauri, the brightest globular cluster as visible from Earth and the largest identified in the Milky Way, possibly a remnant of a dwarf galaxy.
Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae and, as such, form part of the Hubble sequence. Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are often surrounded by a much fainter halo of stars, many of which reside in globular clusters.
A lenticular galaxy is a type of galaxy intermediate between an elliptical and a spiral galaxy in galaxy morphological classification schemes. It contains a large-scale disc but does not have large-scale spiral arms. Lenticular galaxies are disc galaxies that have used up or lost most of their interstellar matter and therefore have very little ongoing star formation. They may, however, retain significant dust in their disks. As a result, they consist mainly of aging stars. Despite the morphological differences, lenticular and elliptical galaxies share common properties like spectral features and scaling relations. Both can be considered early-type galaxies that are passively evolving, at least in the local part of the Universe. Connecting the E galaxies with the S0 galaxies are the ES galaxies with intermediate-scale discs.
The Black Eye Galaxy is a relatively isolated spiral galaxy 17 million light-years away in the mildly northern constellation of Coma Berenices. It was discovered by Edward Pigott in March 1779, and independently by Johann Elert Bode in April of the same year, as well as by Charles Messier the next year. A dark band of absorbing dust partially in front of its bright nucleus gave rise to its nicknames of the "Black Eye", "Evil Eye", or "Sleeping Beauty" galaxy. M64 is well known among amateur astronomers due to its form in small telescopes and visibility across inhabited latitudes.
Centaurus A is a galaxy in the constellation of Centaurus. It was discovered in 1826 by Scottish astronomer James Dunlop from his home in Parramatta, in New South Wales, Australia. There is considerable debate in the literature regarding the galaxy's fundamental properties such as its Hubble type and distance. NGC 5128 is one of the closest radio galaxies to Earth, so its active galactic nucleus has been extensively studied by professional astronomers. The galaxy is also the fifth-brightest in the sky, making it an ideal amateur astronomy target. It is only visible from the southern hemisphere and low northern latitudes.
The Scutum–Centaurus Arm, also known as Scutum-Crux arm, is a long, diffuse curving streamer of stars, gas and dust that spirals outward from the proximate end of the Milky Way's central bar. The Milky Way has been posited since the 1950s to have four spiral arms — numerous studies contest or nuance this number. In 2008, observations using the Spitzer Space Telescope failed to show the expected density of red clump giants in the direction of the Sagittarius and Norma arms. In January 2014, a 12-year study into the distribution and lifespan of massive stars and a 2013-reporting study of the distribution of masers and open clusters both found corroboratory, though would not state irrefutable, evidence for four principal spiral arms.
NGC 1232, also known as the Eye of God Galaxy is an intermediate spiral galaxy about 60 million light-years away in the constellation Eridanus. It was discovered by German-British astronomer William Herschel on 20 October 1784.
NGC 5398 is a barred spiral galaxy in the southern constellation of Centaurus. It was discovered June 3, 1836 by John Herschel. Distance estimates range from 5.39 Mpc to 18.30 Mpc. The tip of the red-giant branch method yields a distance of 11.6 Mpc, while the Tully–Fisher relation shows values of around 8.5 Mpc. It is receding with a heliocentric radial velocity of 1,219 km/s.
NGC 1553 is a prototypical lenticular galaxy in the constellation Dorado. It is the second brightest member of the Dorado Group of galaxies. British astronomer John Herschel discovered NGC 1553 on December 5, 1834 using an 18.7 inch reflector.
NGC 3783 is a barred spiral galaxy located about 135 million light years away in the constellation Centaurus. It is inclined by an angle of 23° to the line of sight from the Earth along a position angle of about 163°. The morphological classification of SBa indicates a bar structure across the center (B) and tightly-wound spiral arms (a). Although not shown by this classification, observers note the galaxy has a luminous inner ring surrounding the bar structure. The bright compact nucleus is active and categorized as a Seyfert 1 type. This nucleus is a strong source of X-ray emission and undergoes variations in emission across the electromagnetic spectrum.
NGC 4698 is a barred spiral galaxy located around 55 million light years away from Earth in the constellation of Virgo. It belongs to the Virgo Cluster of galaxies and is positioned near the northeastern edge of this assemblage. The morphological classification of NGC 4698 in the De Vaucouleurs system is SA(s)ab, which indicates a purely spiral structure with moderate to tightly wound arms. It is inclined to the line of sight from the Earth by an angle of 53° along a position angle of 170°.
NGC 4699 is an intermediate spiral galaxy located in the constellation Virgo. It is located at a distance of about 65 million light years from Earth, which, given its apparent dimensions, means that NGC 4699 is about 85,000 light years across. It was discovered by William Herschel in 1786. It is a member of the NGC 4699 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster.
NGC 3675 is a spiral galaxy located in the constellation Ursa Major. It is located at a distance of circa 50 million light years from Earth, which, given its apparent dimensions, means that NGC 3675 is about 100,000 light years across. It was discovered by William Herschel in 1788.
NGC 3941 is a barred lenticular galaxy located in the constellation Ursa Major. It is located at a distance of circa 40 million light years from Earth, which, given its apparent dimensions, means that NGC 3941 is about 40,000 light years across. It was discovered by William Herschel in 1787.
NGC 4522 is an edge-on spiral galaxy located about 60 million light-years away within the Virgo Cluster in the constellation Virgo. NGC 4522 is losing its molecular gas though ram-pressure stripping as it plows though the cluster at a speed of more than 10 million kilometres per hour. The galaxy was discovered by astronomer John Herschel on January 18, 1828.
NGC 4709 is an elliptical galaxy located in the constellation Centaurus. It is considered to be a member of the Centaurus Cluster and is the dominant member of a small group of galaxies known as "Cen 45" which is currently merging with the main Centaurus Cluster even though the two subclusters' line of sight redshift velocities differ by about 1500 km/s. NGC 4709 was discovered by astronomer James Dunlop on May 7, 1826.
NGC 3081 is a barred lenticular ring galaxy in the constellation of Hydra. NGC 3081 is located about 85 million light-years away from Earth, which means, given its apparent dimensions, that NGC 3081 is approximately 60,000 light-years across. It is a type II Seyfert galaxy, characterised by its bright nucleus. It was discovered by William Herschel on 21 December 1786.
NGC 615 is an unbarred spiral galaxy seen edge-on located in the constellation Cetus. It is located at a distance of circa 70 million light years from Earth, which, given its apparent dimensions, means that NGC 615 is about 75,000 light years across. It was discovered by William Herschel on January 10, 1785. NGC 615 belongs to the NGC 584 galaxy group, which also includes the galaxies NGC 584, NGC 596, NGC 600, and NGC 636.
NGC 7723 is a barred spiral galaxy located in the constellation Aquarius. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 7723 is about 95,000 light years across. It was discovered by William Herschel on November 27, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies 1.5 degrees north-northwest from Omega1 Aquarii. It can be seen with a 4-inch telescope under dark skies.
NGC 7531 is an intermediate spiral galaxy located in the constellation Grus. It is located at a distance of circa 70 million light-years from Earth, which, given its apparent dimensions, means that NGC 7531 is about 95,000 light years across. It was discovered by John Herschel on September 2, 1836.
