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. M

    Dynamics help: variable acceleration and angular velocity

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  2. C

    Using Hubble parameter defn to change integration variable from t to a

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  3. P

    Evaluate the limit by change of variable

    Hey everyone :) Got stuckon a calc question and needed some help, my test is coming up :S Please & thankyouu! Here's the question: Evauate the limit by change of variable: lim (x-->4) [(x^1/2)-2] / [(x^1/3)-8] The answer in the back of the book is 1/12. It MAY be wrong though...
  4. A

    MHB Formula for a geometric series with variable common ratio

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  5. R

    MHB Evaluating a variable expression

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  6. R

    MHB Evaluating a variable expression 2

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  7. K

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  8. C

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  10. T

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  11. V

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  12. T

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  13. A

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  14. Jameson

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  15. W

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  16. Q

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  17. O

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  18. J

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  19. G

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  20. K

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  21. Z

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  22. F

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  23. I

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  24. C

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  25. I

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  26. G

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  27. J

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  29. E

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  30. W

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  31. PhizKid

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  32. L

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  33. M

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  34. A

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  35. U

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  36. S

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  37. O

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  38. N

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  39. B

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  40. B

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  41. K

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  42. A

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  43. A

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  44. A

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  45. A

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  46. T

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  47. F

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  48. A

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  49. C

    Q: How to compute P(X=200 and Y<150)?

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  50. B

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