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How to Find a Star's Diameter

There are few ways to accurately measure a star's diameter. The first, and more accurate way, is used by astronomers. It involves actually measuring a star's velocity at any point in time and measuring the amount of time it takes for a star to travel between two points on its orbit. The star's diameter then can be calculated by multiplying its velocity by the time. However, because most of us lack the equipment to measure a star's velocity, we must resort to simpler measures.

Instructions

- 1
  Look up, either in a textbook or online, the ratio of the luminosity of the star to the luminosity of the sun. Take the square root of this value. You can calculate star radius from the formula (star's radius)/(Sun's radius) = (Sun's temperature/star's temperature)^2 --- Sqrt[star's luminosity/Sun's luminosity].
- 2
  Look up the ratio of the sun's temperature to the star's temperature. Square this value.
- 3
  Calculate the ratio of the star's radius to the Sun's radius by multiplying your value from Step 2 by your value from Step 1.
- 4
  Multiply the value in Step 3 by the radius of the Sun, 695,000 kilometers. This will give you the radius of the star.
- 5
  Multiply the value in Step 4 by 2 to calculate the diameter of the star.

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