Slow irregular variable
Encyclopedia
A slow irregular variable (ascribed the GCVS types L, LB and LC) is a variable
star
that exhibit no or very poorly defined periodicity in their slowly changing light emissions. Most of them are late spectral types
K and M, S stars or carbon star
s. The LB:s are generally giant
s, while the LC:s are supergiant
s exhibiting a light variation interval of about 1 magnitude
.
Examples:
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
that exhibit no or very poorly defined periodicity in their slowly changing light emissions. Most of them are late spectral types
Stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
K and M, S stars or carbon star
Carbon star
A carbon star is a late-type star similar to a red giant whose atmosphere contains more carbon than oxygen; the two elements combine in the upper layers of the star, forming carbon monoxide, which consumes all the oxygen in the atmosphere, leaving carbon atoms free to form other carbon compounds,...
s. The LB:s are generally giant
Giant star
A giant star is a star with substantially larger radius and luminosity than a main sequence star of the same surface temperature. Typically, giant stars have radii between 10 and 100 solar radii and luminosities between 10 and 1,000 times that of the Sun. Stars still more luminous than giants are...
s, while the LC:s are supergiant
Supergiant
Supergiants are among the most massive stars. They occupy the top region of the Hertzsprung-Russell diagram. In the Yerkes spectral classification, supergiants are class Ia or Ib . They typically have bolometric absolute magnitudes between -5 and -12...
s exhibiting a light variation interval of about 1 magnitude
Magnitude (astronomy)
Magnitude is the logarithmic measure of the brightness of an object, in astronomy, measured in a specific wavelength or passband, usually in optical or near-infrared wavelengths.-Background:...
.
Examples:
- L-type: V0341 CarinaeCarina (constellation)Carina is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was formerly part of the larger constellation of Argo Navis until that constellation was divided in three.-Stars:...
, OX GeminorumGemini (constellation)Gemini is one of the constellations of the zodiac. It was one of the 48 constellations described by the 2nd century astronomer Ptolemy and it remains one of the 88 modern constellations today. Its name is Latin for "twins", and it is associated with the twins Castor and Pollux in Greek mythology... - LB-type: AldebaranAldebaranAldebaran is a red giant star located about 65 light years away in the zodiac constellation of Taurus. With an average apparent magnitude of 0.87 it is the brightest star in the constellation and is one of the brightest stars in the nighttime sky...
(Alpha Tauri), Beta PegasiBeta PegasiBeta Pegasi is a star in the constellation Pegasus. Its traditional name is Scheat, a name that has also been used for Delta Aquarii....
, V0569 PuppisPuppisPuppis is a constellation in the southern sky. Its name is the Latin word for the poop deck of a ship, and Puppis represents the deck of the ship and its deckhouses...
(of the clearly naked-eye magnitude 1.85 to 2.74) - LC-type: AntaresAntaresAntares is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky . Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic...
(Alpha Scorpii), Epsilon Pegasi, Beta GruisBeta GruisBeta Gruis is the second brighest star in the southern constellation of Grus. It was once considered the rear star in the tail of the constellation of the Fish: it, with α, δ, θ...