Why are Cepheids called the beacons of the universe? Detailed answer

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Why are Cepheids called the beacons of the universe? Detailed answer

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Why are Cepheids called the beacons of the universe?

Cepheids are a special type of so-called regular variable stars. In the surface layers of Cepheids, the balance of gravitational and gas pressure forces is disturbed. As a result, their radii periodically change by 10-15 percent, and the temperature - by more than 1000 degrees. At the same time, the apparent brightness of stars also changes periodically.

The Cepheids take their name from the prototype star Delta Cephei, which varies in magnitude from 3,6 to 4,3 with a period of 5,4 days.

As was established in 1912, the periods of change in the brightness of Cepheids are closely related to their luminosity. This connection determined the exceptional importance of these stars for measuring extragalactic distances. By finding a Cepheid in another galaxy and measuring its period of pulsation, one can determine its luminosity (absolute magnitude).

By comparing this value with the apparent brightness (visual magnitude), one can estimate the distance to the Cepheid, and hence to the galaxy in which it is located. This is why the Cepheids are sometimes called the beacons of the universe.

Author: Kondrashov A.P.

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