A variable star is a star whose brightess as seen from Earth (its apparent magnitude) fluctuates.
This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either:
- Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks.
- Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it.
Many, possibly most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11 year solar cycle.
Other articles related to "variable star, stars, star":
... Stars with planets may also show brightness variations if their planets pass between the earth and the star ...
... Peltier Award in 1981 for his variable star and lunar occultation observations and contributions to artificial satellite programs ... The American Association of Variable Star Observers honoured him with the Merit Award in 1988, for his record of more than 50,000 observations in the AAVSO ... Award of the Astronomical Society of the Pacific for his variable star and occultation observations in 1997 ...
... The novel Variable Star was written by Spider Robinson based on an outline created by Heinlein and found after his death ...
... The star system was discovered in 1948 by Willem Jacob Luyten in the course of compiling a catalog of stars of high proper motion he noted its exceptionally high proper motion of 3.37 arc seconds ... The two stars are of nearly equal brightness, with visual magnitudes of 12.57 and 11.99 as seen from Earth ... The distance between the two stars varies from 2.1 to 8.8 astronomical units (310 to 1,320 Gm) ...
... Despite its size, Hydra contains only one reasonably bright star, Alphard, designated Alpha Hydrae ... Beta Hydrae is a blue-white star of magnitude 4.3, 365 light-years from Earth ... Hydra has one bright binary star, Epsilon Hydrae, which is difficult to split in amateur telescopes it has a period of 1000 years and is 135 light-years from Earth ...
Famous quotes containing the words star and/or variable:
“Our star was brighter perhaps when it had water in it.
Now there is no question even of that, but only
Of holding on to the hard earth so as not to get thrown off,
With an occasional dream, a vision ...”
—John Ashbery (b. 1927)
“There is not so variable a thing in nature as a ladys head-dress.”
—Joseph Addison (16721719)