Cepheid I（δ Cep/Cepheid variable ）YesCepheusInternal distanceearthAbout 891Light yearA pair ofConjoint starThe apparent magnitude varies from 3.48 to 4.37.It isCepheid variableThe prototype of this type of variable star is also the closestsunlightOne (the otherPolarisCloser).[3]He wasJohn Goodricke It was found to be a variable star, which was earlier in the same yearSky beam four(Aquila η) The second one found afterCepheid variable。[4]
Its dimming period is 5.37 days, and the brightness decreases from 3.5 to 4.4.Cepheid is a binary star, and the main star is a yellow supergiant or bright giant, 2200 times brighter and 41 times larger than the sun.The companion star is blue and white, its spectral type is B6, and its surface temperature reaches about 14000K, 3.5 times larger than the sun.Although the diameter and luminosity of the main star are far greater than that of the companion star, the difference in mass between the two stars is not significant. The main star has a mass of 5.4 times that of the sun, and the companion star has a mass of 4 to 4.5 times that of the sun.Their age and origin can be inferred from their mass.Cepheid I is about 70 million years old and belongs to the constellation Cepheus OB6.
Cepheid is a yellow supergiant with low luminosity, which can be said to be between a giant star and a supergiant, so its mass is not enough to make it explode as a supernova, and it should eventually shrink into a white dwarf with high mass.
The changes of Cepheid I's luminosity and spectral type are caused by the pulsation of stars.The spectral type of this star varies from F5 to G3 in 5.36634 days (5 days, 8 hours, 47 minutes and 32 seconds).The brighter main star in the binary star is yellowish whiteF-type supergiant；Its companion star is a B-type star, located at 41secondIn addition, the apparent magnitude is 7.5.
Cepheid I has an average magnitude of 4.07.[3]
Cepheid variable
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usuallyCepheid variableWhen the star first formed, its mass was 3-30 times that of the sun, and then passed as a B-type starMain order bandOnce they burn out the hydrogen in their core, their helium core loses its stability, starts to shrink and expand regularly, and goes through the helium combustion phase.Cepheid variable stars are massive stars in the late life stage. They are bright enough to be seen with the naked eye, and are easily located in the adjacentGalaxyFound in.Since the brightness of a star is directly related to its pulsation period, astronomers only need to measure theApparent magnitude, we can determine their distance and the distance of the star's galaxy.[3]
