What measurements do scientist use to measure stars?

Answer 1

Hi. It is a pleasure to help. If you mean the distance from the earth to the stars, astronomers use a technique called parallax which is a way to infer the distance to a star based on triangulation. Astronomers use a unit called the light-year, which is the distance travelled by the light in one year. Since light travels at a speed of 300,000 km/s, in one year light leaves behind a distance of 9.4605284 × 1015 meters. Some stars are only a few light- years away. Others are very far away, in the limits of the observable universe. If the astronomer wants to measure the distance to a very far away star, then parallax is no longer useful. Other techniques and properties are employed such as the Cepheids, which are a very particular class of stars in which the period of variation in their brightness is related to their distances. So by measuring the period, astronomers are able to infer the distance.

Measuring distances to stars and to distant galaxies is one of the central problems in Astronomy. It is VERY important. Several research efforts are devoted to measuring distances. In fact, in the 1920's E. Hubble first measured the distance to other galaxies using cepheids. The Hubble Sapce Telescope still measures distances to distant galaxies using a variety of observational techniques.

If you mean the measurement of the radius of a star, astronomers do that by knowing the details of the cameras used to photograph the star and the known distance to it. Sometimes studying the properties of the light emitted by stars it is possible to infer its radius based on the theory of stellar evolution.

Prof. João Rodrigo Leão

Rio Grande Federal University - Brazil