Stellar phenomena

type of stellar remnant composed mostly of electron-degenerate matter

high-speed, i.e. high-energy particle, mainly originating in outer space, outside the Solar system

thumb|right|223x223px|PSR B1509−58 – [[X-rays from Chandra are gold; infrared from WISE in red, green and blue/max.]] thumb|right|Animation of a rotating pulsar. The sphere in the middle represents the neutron star, the curves indicate the magnetic field lines and the protruding cones represent the emission zones. thumb|Illustration of the "lighthouse" effect produced by a pulsar

type of small and relatively-cool star

type of substellar object larger than a gas giant

frame|right|Artist's conception of a white dwarf, right, Accretion (astrophysics)|accreting hydrogen from the [[Roche lobe of its larger companion star]]

thumb|Artist's conception of a powerful magnetar in a star cluster

flashes of gamma rays from distant galaxies

Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram, with absolute visual magnitudes between about −3 and −8. The temperatures of supergiant stars range from about 3,400 K to over 20,000 K.

A hypergiant (luminosity class 0, Ia-0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classi

thumb|upright=1.4|European Southern Observatory|ESO image of hypernova [[SN 1998bw in a spiral arm of galaxy ESO 184-G82]] A hypernova is a very energetic supernova which is believed to result from an extreme core collapse scenario. In this case, a massive star (>30 solar masses) collapses to form a rotating black hole emitting twin astrophysical jets and surrounded by an accretion disk. It is a type of stellar explosion that ejects material with an unusually high kinetic energy, an order of magnitude higher than most supernovae, with a luminosity at least 10 times greater. Hypernovae release

stars with a supergiant luminosity class

stars of early spectral type

significant release of plasma and magnetic field from the solar corona

(of a star) layer which is unstable to convection. Energy is primarily or partially transported by convection in such a region

thumb|290px|Artist's impression of a micronovaA micronova is a putative type of thermonuclear explosion on the surface of a white dwarf much smaller than the strength of a nova; being about in strength, about a millionth that of a typical nova. The phenomenon was first described in April 2022.

Helioseismology is the study of the structure and dynamics of the Sun through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surface. It is similar to geoseismology, or asteroseismology, which are respectively the studies of the Earth or stars through their oscillations. While the Sun's oscillations were first detected in the early 1960s, it was only in the mid-1970s that it was realized that the oscillations propagated throughout the Sun and could allow scientists to study the Sun's deep interior. The term was

high-energy astrophysical phenomenon manifested as a transient radio pulse lasting only a few milliseconds

thumb|Different oscillation modes have different sensitivities to the structure of a star. By observing multiple modes, one can therefore partially infer a star's internal structure. Asteroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the local speed of sound, which in turn depends on local temperature and chemical composition. Because the resulting oscillation modes are sensitive to different parts of the star, they inform astronomers about the internal structure of the star, whic

thumb|upright=1.4|Artist's impression of neutron stars merging, producing gravitational waves and resulting in a kilonova

stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state

phenomenon of stars

massive star with an extended atmosphere

measure of sunspots

chromospheric signature of a large-scale solar coronal shock wave. generated by solar flares, discovered by Gail Moreton and Harry E. Ramsey in 1959

physical process in highly conducting plasmas in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy, and particle acceleration

type of cataclysmic variable binary star system

astronomical phenomenon

bright region in the chromosphere of the Sun

Class of X-ray binary stars

Starspots are stellar phenomena, so-named by analogy with sunspots. Spots as small as sunspots have not been detected on other stars, as they would cause undetectably small fluctuations in brightness. The commonly observed starspots are in general much larger than those on the Sun: up to about 30% of the stellar surface may be covered, corresponding to starspots 100 times larger than those on the Sun.

pulling apart of a star by tidal forces when it gets too close to a supermassive black hole

type of variable star

variation in period and amplitude in RR Lyrae type variable stars

unexplained circular astronomical object detected only by radio waves

violent reignition of thermonuclear fusion in a white dwarf star

thumb | right | alt=Illustration of a bright plume coming out of a star | Artist's impression of a superflare from EV Lacertae Superflares are very strong explosions observed on stars with energies up to ten thousand times that of typical solar flares. The stars in this class satisfy conditions which should make them solar analogues, and would be expected to be stable over very long time scales. The original nine candidates were detected by a variety of methods. No systematic study was possible until the launch of the Kepler space telescope, which monitored a very large number of solar-type st

mechanism explaining sunspot patterns

ionized plasma found in astrophysical environments

astronomical phenomenon where rapidly rotating star has brighter poles and darker equator

high-energy astrophysical process

Physical phenomenon

Type of x-ray binary

research project to observe air showers

supernova in the NGC 5253 galaxy, first observed in 1972.

thumb|right|upright=1.4|Light curve of eclipsing dwarf nova HT Cassiopeiae during outburst, showing [[eclipses and SU Ursae Majoris-type superhumps]] In astronomy, a superhump is a periodic brightness variation in a cataclysmic variable star system, with a period within a few percent of the orbital period of the system.

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