NGC 755 | |
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![]() NGC 755 as seen from the Sloan Digital Sky Survey | |
Observation data (J2000 epoch) | |
Constellation | Cetus |
Right ascension | 01h 56m 22.685s [1] |
Declination | −09° 03′ 41.15″ [1] |
Redshift | 0.005490 [1] |
Heliocentric radial velocity | 1641.2 km/s [1] |
Distance | 69 Mly (21.3 Mpc) [2] |
Apparent magnitude (B) | 13.2 [1] |
Absolute magnitude (V) | −18.27 |
Characteristics | |
Type | SBcd [1] |
Other designations | |
NGC 763, MCG -02-06-005, PGC 7262 [1] |
NGC 755 is an emission line spiral galaxy in the constellation of Cetus. [1] [3] The galaxy's velocity of 1641.2 km/s was used to calculate its distance using the Tully–Fisher relation. [1] [2] Its dark matter halo was found to be core-dominated, in agreement with predictions from the lambda-CDM model of cosmology. [2]
The rotation curve of a disc galaxy is a plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy's centre. It is typically rendered graphically as a plot, and the data observed from each side of a spiral galaxy are generally asymmetric, so that data from each side are averaged to create the curve. A significant discrepancy exists between the experimental curves observed, and a curve derived by applying gravity theory to the matter observed in a galaxy. Theories involving dark matter are the main postulated solutions to account for the variance.
NGC 3109 is a small barred Magellanic type spiral or irregular galaxy around 4.35 Mly away in the direction of the constellation of Hydra. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy Antlia Dwarf. It was discovered by John Herschel on March 24, 1835 while he was in what is now South Africa.
In modern models of physical cosmology, a dark matter halo is a basic unit of cosmological structure. It is a hypothetical region that has decoupled from cosmic expansion and contains gravitationally bound matter. A single dark matter halo may contain multiple virialized clumps of dark matter bound together by gravity, known as subhalos. Modern cosmological models, such as ΛCDM, propose that dark matter halos and subhalos may contain galaxies. The dark matter halo of a galaxy envelops the galactic disc and extends well beyond the edge of the visible galaxy. Thought to consist of dark matter, halos have not been observed directly. Their existence is inferred through observations of their effects on the motions of stars and gas in galaxies and gravitational lensing. Dark matter halos play a key role in current models of galaxy formation and evolution. Theories that attempt to explain the nature of dark matter halos with varying degrees of success include cold dark matter (CDM), warm dark matter, and massive compact halo objects (MACHOs).
NGC 4565 is an edge-on spiral galaxy about 30 to 50 million light-years away in the constellation Coma Berenices. It lies close to the North Galactic Pole and has a visual magnitude of approximately 10. It is known as the Needle Galaxy for its narrow profile. First recorded in 1785 by William Herschel, it is a prominent example of an edge-on spiral galaxy.
NGC 5170 is a large, nearby, edge-on spiral galaxy in the equatorial constellation of Virgo. It was discovered on February 7, 1785 by William Herschel. This galaxy is located at a distance of 83.5 million light years and is receding at a heliocentric radial velocity of 1,502 km/s. It 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 4244, also known as Caldwell 26, is an edge-on loose spiral galaxy in the constellation Canes Venatici, and is part of the M94 Group or Canes Venatici I Group, a galaxy group relatively close to the Local Group containing the Milky Way. In the sky, it is located near the yellow naked-eye star, Beta Canum Venaticorum, but also near the barred spiral galaxy NGC 4151 and irregular galaxy NGC 4214.
NGC 4889 is an E4 supergiant elliptical galaxy. It was discovered in 1785 by the British astronomer Frederick William Herschel I, who catalogued it as a bright, nebulous patch. The brightest galaxy within the northern Coma Cluster, it is located at a median distance of 94 million parsecs from Earth. At the core of the galaxy is a supermassive black hole that heats the intracluster medium through the action of friction from infalling gases and dust. The gamma ray bursts from the galaxy extend out to several million light years of the cluster.
NGC 5907 is a spiral galaxy located approximately 50 million light years from Earth. William Herschel discovered the galaxy in 1788.
NGC 1288 is an intermediate barred spiral galaxy located about 196 million light years away in the constellation Fornax. In the nineteenth century, English astronomer John Herschel described it as "very faint, large, round, very gradually little brighter middle." The morphological classification of SABc(rs) indicates weak bar structure across the nucleus (SAB), an incomplete inner ring orbiting outside the bar (rs), and the multiple spiral arms are moderately wound (c). The spiral arms branch at intervals of 120° at a radius of 30″ from the nucleus. The galaxy is most likely surrounded by a dark matter halo, giving it a mass-to-light ratio of 14 M☉/L☉.
NGC 157 is an intermediate spiral galaxy in the constellation of Cetus, positioned about 4° east of the star Iota Ceti. This galaxy can be viewed from suburban skies using a moderate-sized telescope. It was discovered on December 13, 1783 by William Herschel. The compiler of the New General Catalogue, John Louis Emil Dreyer noted that NGC 157 was "pretty bright, large, extended, between 2 considerably bright stars". It is a relatively isolated galaxy; the nearest other galaxy of comparable luminosity lies at a separation of 4.2 Mly (1.3 Mpc).
NGC 289 is a spiral galaxy in the southern constellation of Sculptor, located at a distance of 76 megalight-years from the Milky Way. It was discovered on September 27, 1834, by John Herschel. The compiler of the New General Catalogue, John Louis Emil Dreyer, noted that NGC 289 was "pretty bright, large, extended, between 2 considerably bright stars". The plane of the galaxy is inclined by an angle of 45° to the line of sight from the Earth.
NGC 4494 is an elliptical galaxy located in the constellation Coma Berenices. It is located at a distance of circa 45 million light years from Earth, which, given its apparent dimensions, means that NGC 4494 is about 60,000 light years across. It was discovered by William Herschel in 1785.
NGC 5949 is a dwarf spiral galaxy located around 44 million light-years away in the constellation Draco. NGC 5949 was discovered in 1801 by William Herschel, and it is 30,000 light-years across. NGC 5949 is not known to have an Active galactic nucleus, and it is not known for much star-formation.
NGC 720 is an elliptical galaxy located in the constellation Cetus. It is located at a distance of circa 80 million light years from Earth, which, given its apparent dimensions, means that NGC 720 is about 110,000 light years across. It was discovered by William Herschel on October 3, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies about three and a half degrees south and slightly east from zeta Ceti.
NGC 2525 is a barred spiral galaxy located in the constellation Puppis. It is located at a distance of about 70 million light years from Earth, which, given its apparent dimensions, means that NGC 2525 is about 60,000 light years across. It was discovered by William Herschel on February 23, 1791.
NGC 2974 is a lenticular galaxy located in the constellation Sextans. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 2974 is about 90,000 light years across. It was discovered by William Herschel on January 6, 1785. NGC 2974 is located in the sky about 2 and a half degrees south-south east of Iota Hydrae and more than 6 degrees northeast of Alphard. A 10th magnitude star lies next to the galaxy, thus making it a challenging object at low magnifications. NGC 2974 is part of the Herschel 400 Catalogue.
NGC 3741 is an irregular galaxy in the constellation Ursa Major. It was discovered by John Herschel on March 19, 1828. At a distance of about 10 million light-years, it is located in the M94 Group. It is relatively undisturbed by other galaxies.
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 7507 is an elliptical galaxy located in the constellation Sculptor. It was discovered by the German-British astronomer William Herschel on October 30, 1783. The galaxy lies at an estimated distance of 80.1 million light-years (24.55 Mpc) from the Milky Way, and has an angular size of 2.0′ × 1.9′ in the near infrared. It is receding with a heliocentric radial velocity of 1,590 km/s.
NGC 5963 is a spiral galaxy in the northern constellation of Draco. It was discovered on May 5, 1788 by German-British astronomer William Herschel. NGC 5963 has an apparent visual magnitude of 13.1 and is located at a distance of 42 million light-years (13.0 Mpc) from the Milky Way galaxy. It has an angular separation of just 9′ from NGC 5965, but the two galaxies are not physically related. Although it is relatively isolated, NGC 5963 is sometimes classified as a member of the NGC 5866 Group of galaxies.