Charles MessierCharles Messier (French:; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the Messier objects, referred to with the letter M and their number between 1 and 110. Messier's purpose for the catalogue was to help astronomical observers distinguish between permanent and transient visually diffuse objects in the sky.
Andromeda GalaxyBarred spiral galaxy in the Local GroupThe Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a D25 isophotal diameter of about 46.56 kiloparsecs (152,000 light-years) and is approximately 765 kpc (2.5 million light-years) from Earth.
Messier objectAstronomical objects catalogued by Charles MessierThe Messier objects are a set of 110 astronomical objects catalogued by the French astronomer Charles Messier in his Catalogue des Nébuleuses et des Amas d'Étoiles [fr] (Catalogue of Nebulae and Star Clusters). Because Messier was interested only in finding comets, he created a list of those non-comet objects that frustrated his hunt for them.
Local GroupThe Local Group is the galaxy group that includes the Milky Way, where Earth is located. It consists of two collections of galaxies in a "dumbbell" shape; the Milky Way and its satellite galaxies form one lobe, and the Andromeda Galaxy and its satellite galaxies constitute the other.
Messier 32Messier 32 (also known as M32 and NGC 221) is a dwarf "early-type" galaxy about 2,490,000 light-years (760,000 pc) from the Solar System, appearing in the constellation Andromeda. M32 is a satellite galaxy of the Andromeda Galaxy (M31) and was discovered by Guillaume Le Gentil in 1749. The galaxy is a prototype of the relatively rare compact elliptical (cE) class. Half the stars are concentrated within the inner core, which has an effective radius of 330 light-years (100 pc).
Dwarf elliptical galaxyDwarf elliptical galaxies (dEs) are elliptical galaxies that are smaller than ordinary elliptical galaxies. They are quite common in galaxy groups and clusters, and are usually companions to other galaxies.
William HerschelFrederick William Herschel ( ; German: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German–British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline Herschel. Born in the Electorate of Hanover, he followed his father into the military band of Hanover, before emigrating to Britain in 1757 at the age of 19.
Caroline HerschelCaroline Lucretia Herschel ( , German:; 16 March 1750 – 9 January 1848) was a German astronomer, whose most significant contributions to astronomy were the discoveries of several comets, including the periodic comet35P/Herschel–Rigollet, which bears her name. She was the younger sister of astronomer William Herschel, with whom she worked for most of her career.
Satellite galaxyA 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). Satellite galaxies and their constituents are bound to their host galaxy, in the same way that planets within the Solar System are gravitationally bound to the Sun. While most satellite galaxies are dwarf galaxies, satellite galaxies of large galaxy clusters can be much more massive.
Galaxy morphological classificationGalaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance, shape, structure, and distribution of light. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence, devised by Edwin Hubble and later expanded by Gérard de Vaucouleurs and Allan Sandage.
Supermassive black holeA supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (M☉). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space that nothing, not even light, can escape.
FlatteningFlattening is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution (spheroid) respectively. Other terms used are ellipticity, or oblateness.*As an Amazon Associate I earn from qualifying purchases.