30 relations: Active galactic nucleus, Andromeda Galaxy, Caldwell catalogue, Cassiopeia (constellation), Catalogue of Nebulae and Clusters of Stars, Constellation, Crossley telescope, Dwarf spheroidal galaxy, Epoch (astronomy), James Edward Keeler, John Herschel, Kilometre, Lick Observatory, Light-year, List of Andromeda's satellite galaxies, Local Group, New General Catalogue, Orders of magnitude (length), Parsec, Principal Galaxies Catalogue, Satellite galaxy, Second, Seyfert galaxy, Star cluster, Star formation, Supernova remnant, Tip of the red-giant branch, Uppsala General Catalogue, Walter Baade, William Herschel.
An active galactic nucleus (AGN) is a compact region at the center of a galaxy that has a much higher than normal luminosity over at least some portion—and possibly all—of the electromagnetic spectrum, with characteristics indicating that the excess luminosity is not produced by stars.
The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224, is a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way.
The Caldwell Catalogue is an astronomical catalogue of 109 star clusters, nebulae, and galaxies for observation by amateur astronomers.
Cassiopeia is a constellation in the northern sky, named after the vain queen Cassiopeia in Greek mythology, who boasted about her unrivalled beauty.
The Catalogue of Nebulae and Clusters of Stars (CN) is an astronomical catalogue of nebulae first published in 1786 by William Herschel, with the assistance of his sister Caroline Herschel.
A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices.
The Crossley telescope is a reflecting telescope located at Lick Observatory in the U.S. state of California.
A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population.
In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as the celestial coordinates or elliptical orbital elements of a celestial body, because these are subject to perturbations and vary with time.
James Edward Keeler (September 10, 1857 – August 12, 1900) was an American astronomer.
Sir John Frederick William Herschel, 1st Baronet (7 March 1792 – 11 May 1871) was an English polymath, mathematician, astronomer, chemist, inventor, experimental photographer who invented the blueprint, and did botanical work.
The kilometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: km; or) or kilometer (American spelling) is a unit of length in the metric system, equal to one thousand metres (kilo- being the SI prefix for). It is now the measurement unit used officially for expressing distances between geographical places on land in most of the world; notable exceptions are the United States and the road network of the United Kingdom where the statute mile is the official unit used.
The Lick Observatory is an astronomical observatory, owned and operated by the University of California.
The light-year is a unit of length used to express astronomical distances and measures about 9.5 trillion kilometres or 5.9 trillion miles.
The Andromeda Galaxy (M31) has satellite galaxies just like the Milky Way.
The Local Group is the galaxy group that includes the Milky Way.
The New General Catalogue of Nebulae and Clusters of Stars (abbreviated as NGC) is a catalogue of deep-sky objects compiled by John Louis Emil Dreyer in 1888.
The following are examples of orders of magnitude for different lengths.
The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System.
The Catalogue of Principal Galaxies (PGC) is an astronomical catalog published in 1989 that lists B1950 and J2000 equatorial coordinates and cross-identifications for 73,197 galaxies.
A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy (also known as the primary galaxy).
The second is the SI base unit of time, commonly understood and historically defined as 1/86,400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each.
Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars.
Star clusters are groups of stars.
Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars.
A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova.
Tip of the red-giant branch (TRGB) is a primary distance indicator used in astronomy.
The Uppsala General Catalogue of Galaxies (UGC) is a catalogue of 12,921 galaxies visible from the northern hemisphere.
Wilhelm Heinrich Walter Baade (March 24, 1893 – June 25, 1960) was a German astronomer who worked in the United States from 1931 to 1959.
Frederick William Herschel, (Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer, composer and brother of fellow astronomer Caroline Herschel, with whom he worked.