What Are Cepheid Variables?
Cepheid variable stars are a type of variable star. Its light-changing period (that is, the time for one week of brightness change) is directly proportional to its luminosity, so it can be used to measure the distance between interstellar and intergalactic systems. Most of these variable stars are type F stars (hot stars of moderate temperature) when the luminosity is extremely high; type G stars (cold stars like the sun) when the luminosity is extremely small. A typical star is Cepheus. In 1784, John Goodley discovered the phenomenon of light variation, and in 1912, Levitt of the Harvard Observatory discovered the period-photometric relationship of the Cepheid variable star.
Cepheid Variable Star
- On September 10, 1784, Edward Piggott detected a photometric change in in Aquila
- 1908-1912, American astronomer
- Cepheid variable stars actually include two types with different properties: Star family I Cepheid variable stars (or called
- in
- The accepted explanation of the pulsation of Cepheid variable stars today is called the Eddington valve , or -mechanism , where the Greek letter (kappa) stands for gas opacity.
- Because Cepheid variable stars have a definite peripheral light relationship, when measuring the distances of star clusters and galaxies, as long as the Cepheid variable stars are observed, they can be used to determine their distance. As a result, Cepheid variable stars are called "meter scales". The famous American astronomer Hubble used the Cepheid variable star in the Andromeda galaxy to determine the distance of the Andromeda galaxy, and then Bud corrected it, confirming that it is an extragalactic galaxy.
- There are Cepheid variable stars in both star families, but their Zhou Guang relationship is different. Therefore, the ranging formula should be selected according to the type of the Cepheid variable star.
- Star group I Cepheid variable star: Mp = -1.43-2.81lgP
- Star group II Cepheid variable star: Mp = -0.35-1.75lgP
- Where Mp is the absolute magnitude of the photo and P is the period in days.
- Cepheid Variable Star-Reference 1, "World of Galaxy"
- Zhou Guang relationship
- 3. Lyra variable star
- 4, pulsating variable stars