Stars & Stellar Phenomena
Notable stars, stellar types, nebulae, and the life cycles of stars
Astronomy: Aldebaran
Aldebaran Aldebaran (Arabic: الدَّبَرَان, lit. 'The Follower') is a star in the zodiac constellation of Taurus....
Astronomy: Alpha Centauri
Alpha Centauri Alpha Centauri (α Centauri, α Cen, or Alpha Cen) is a star system in the southern constellation of Centaurus. It consists of three stars: Rigil Kentaurus (α Centauri A), Toliman (α Cen...
Astronomy: Antares
Antares Antares is the brightest star in the constellation of Scorpius. It has the Bayer designation α Scorpii, which is Latinised to Alpha Scorpii....
Astronomy: Arcturus
Arcturus Arcturus is a red giant star in the northern constellation of Boötes, and the brightest star in the constellation. It has the Bayer designation α Boötis, which is Latinized to Alpha Boötis a...
Astronomy: Betelgeuse
Betelgeuse Betelgeuse is a red supergiant star in the equatorial constellation of Orion. It is usually the tenth-brightest star in the night sky and, after Rigel, the second brightest in its constell...
Astronomy: Binary Star Systems
Binary Star Systems A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars are among the most important objects in...
Astronomy: Black Holes
Black Holes A black hole is an astronomical body so compact that its gravity prevents anything, including light, from escaping. Albert Einstein's theory of general relativity, which describes gravita...
Astronomy: Brown Dwarfs
Brown Dwarfs Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their mass is approximately 13 to 80 time...
Astronomy: Canopus
Canopus Canopus is the brightest star in the southern constellation of Carina and the second-brightest star in the night sky. It is designated α Carinae, which is romanized (transliterated) to Alpha ...
Astronomy: Capella
Capella Capella is the brightest star in the northern constellation of Auriga. It has the Bayer designation α Aurigae, which is Latinised to Alpha Aurigae and abbreviated Alpha Aur or α Aur....
Astronomy: Carina Nebula
Carina Nebula The Carina Nebula or Eta Carinae Nebula (catalogued as NGC 3372; also known as the Great Carina Nebula) is a large, complex area of bright and dark nebulosity in the constellation Carin...
Astronomy: Cat's Eye Nebula
Cat's Eye Nebula The Cat's Eye Nebula (also known as NGC 6543 and Caldwell 6) is a planetary nebula in the northern constellation of Draco, discovered by William Herschel on February 15, 1786. It was...
Astronomy: Cepheid Variables
Cepheid Variables A Cepheid variable () is a type of variable star that pulsates radially, varying in both diameter and temperature. It changes in brightness, with a well-defined stable period (typic...
Astronomy: Crab Nebula
Crab Nebula The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus. The common name comes from a drawing that som...
Astronomy: Deneb
Deneb Deneb () is a blue supergiant star in the constellation of Cygnus. It is the brightest star in the constellation and the 19th brightest in the night sky, with an apparent magnitude slightly var...
Astronomy: Eagle Nebula
Eagle Nebula The Eagle Nebula (catalogued as Messier 16 or M16, and as NGC 6611, and also known as the Star Queen Nebula) is a young open cluster of stars in the constellation Serpens, discovered by ...
Astronomy: Helix Nebula
Helix Nebula The Helix Nebula (also known as NGC 7293 or Caldwell 63) is a planetary nebula (PN) located in the constellation Aquarius. Discovered by Karl Ludwig Harding, most likely before 1824, thi...
Astronomy: Horsehead Nebula
Horsehead Nebula The Horsehead Nebula (also known as Barnard 33 or B33) is a small dark nebula located about 1,375 light-years (422 pc) from Earth in the constellation of Orion. The nebula is located...
Astronomy: Lagoon Nebula
Lagoon Nebula The Lagoon Nebula (catalogued as Messier 8 or M8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is a giant emission nebula with an H II region located in the constellation Sagittarius. D...
Astronomy: Magnetars
Magnetars A magnetar is a type of neutron star with an extremely powerful magnetic field (~109 to 1011 T, ~1013 to 1015 G). The magnetic-field decay (or dissipation) powers the emission of high-energ...
Astronomy: Main Sequence Stars
Main Sequence Stars In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars spend the majorit...
Astronomy: Neutron Stars
Neutron Stars A neutron star is the gravitationally collapsed core of a massive supergiant star. It results from the supernova explosion of a massive star—combined with gravitational collapse—that co...
Astronomy: Orion Nebula
Orion Nebula The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula in the Milky Way situated south of Orion's Belt in the constellation of Orion, and is known as the middl...
Astronomy: Pillars of Creation
Pillars of Creation Pillars of Creation is a photograph taken by the Hubble Space Telescope that depicts elephant trunks of interstellar gas and dust in the Eagle Nebula of the Serpens constellation,...
Astronomy: Planetary Nebulae
Planetary Nebulae A planetary nebula is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula...
Astronomy: Polaris
Polaris Polaris is a yellow supergiant star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris (Latinized to Alpha Ursae Minoris) and is commonly called the Nor...
Astronomy: Protostars
Protostars A protostar is a very young star that is still gathering mass from its parent molecular cloud. It is the earliest phase in the process of stellar evolution....
Astronomy: Proxima Centauri
Proxima Centauri Proxima Centauri is the nearest star to Earth after the Sun, located 4.25 light-years (1.3 parsecs) away in the southern constellation of Centaurus. Discovered in 1915 by Robert Inne...
Astronomy: Pulsars
Pulsars A pulsar (pulsating star, on the model of quasar) is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be o...
Astronomy: Red Giant Stars
Red Giant Stars A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses (M☉)) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, ...
Astronomy: Rigel
Rigel Rigel is a blue supergiant star in the equatorial constellation of Orion. It has the Bayer designation β Orionis, which is Latinized to Beta Orionis and abbreviated Beta Ori or β Ori....
Astronomy: Ring Nebula
Ring Nebula The Ring Nebula is a planetary nebula in the northern constellation of Lyra, about mid-way between the prominent stars Beta and Gamma Lyrae. It is also catalogued as Messier 57, M57 and N...
Astronomy: Sirius
Sirius Sirius is the brightest star in the night sky, located in the southern constellation of Canis Major. Its name is derived from the Greek word Σείριος (Latin script: Seirios; lit....
Astronomy: Spica
Spica Spica is the brightest object in the constellation of Virgo and one of the 20 brightest stars in the night sky. It has the Bayer designation α Virginis, which is Latinised to Alpha Virginis and...
Astronomy: Stellar Black Holes
Stellar Black Holes A stellar black hole (or stellar-mass black hole) is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar ma...
Astronomy: Stellar Evolution
Stellar Evolution Stellar evolution is the process by which a star changes over the course of time. Depending on the mass of the star, its lifetime can range from a few million years for the most mas...
Astronomy: Stellar Nucleosynthesis
Stellar Nucleosynthesis In astrophysics, stellar nucleosynthesis is the creation of chemical elements by nuclear fusion reactions within stars. Stellar nucleosynthesis has occurred since the original...
Astronomy: Supernova 1987A
Supernova 1987A SN 1987A was a Type II supernova in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It occurred approximately 51.4 kiloparsecs (168,000 light-years) from Earth ...
Astronomy: Supernovae
Supernovae A supernova (pl.: supernovae) is a powerful and luminous explosion of a star. A supernova occurs during the last evolutionary stages of a massive star, or when a white dwarf is triggered i...
Astronomy: Tarantula Nebula
Tarantula Nebula The Tarantula Nebula (also known as 30 Doradus) is a large H II region in the Large Magellanic Cloud (LMC), forming its south-east corner (from Earth's perspective)....
Astronomy: The H-R Diagram
The H-R Diagram A Hertzsprung–Russell diagram (abbreviated as H–R diagram, HR diagram or HRD) is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminositie...
Astronomy: Variable Stars
Variable Stars A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes systematically with time. This variation may be caused by a change in emitted light or by...
Astronomy: Vega
Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr....
Astronomy: White Dwarf Stars
White Dwarf Stars A white dwarf is a very dense type of star: in an Earth-sized volume, it packs a mass that is comparable to the Sun. A white dwarf radiates light from residual heat, not from nuclea...