What is Variable: Definition and 1000 Discussions

A variable star is a star whose brightness 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.

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  1. B

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  2. M

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  4. W

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  5. F

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  6. F

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  7. E

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  9. A

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  11. A

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  13. R

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  14. G

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  15. R

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  17. E

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  18. F

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  19. nomadreid

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  22. S

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  24. M

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  27. X

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  30. N

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  33. I

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  35. A

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  36. Eucliwood

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  37. R

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  38. user366312

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  39. W

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  40. E

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  41. E

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  42. Ranku

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  43. DrClaude

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  44. CivilSigma

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  45. R

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  46. Ottodomus

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  47. jk22

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  48. N

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  49. A

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  50. R

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