Delta Cephei
Delta Cephei is a star in the constellation Cepheus, notable for being the prototype of the Cepheid variable stars, a class of stars whose luminosity varies periodically. Here are some key details about Delta Cephei:
- Location: Delta Cephei is located at right ascension 22h 29m 10.26s and declination +58° 24' 54.7". It is approximately 887 light-years from Earth.
- Discovery: The variability of Delta Cephei was discovered by John Goodricke in 1784. Goodricke, an English astronomer, observed that the star's brightness varied with a period of 5.36634 days.
- Variability: Delta Cephei is the archetype of Cepheid variables, stars that pulsate radially, causing their brightness to change over time. Its apparent magnitude oscillates between +3.5 and +4.4, making it visible to the naked eye.
- Physical Characteristics:
- Spectral Type: Delta Cephei has a spectral type of F5Ib-G2Ib, which means it changes its spectral type over the course of its pulsation cycle.
- Radius: Its radius varies from 44 to 46 times that of the Sun.
- Luminosity: It is about 1,900 times brighter than the Sun.
- Temperature: The surface temperature of Delta Cephei changes from about 6,000 K to 5,500 K during its pulsation.
- Importance: The study of Delta Cephei and other Cepheid variables has been crucial in understanding stellar evolution and in measuring distances within our galaxy and beyond. The Period-Luminosity Relationship, first discovered by Henrietta Swan Leavitt, allows astronomers to use Cepheids as "standard candles" for distance determination.
- Historical Context: The discovery of Delta Cephei's variability marked a significant advancement in astronomy. It provided the first example of a star with a predictable change in brightness, which later helped in understanding stellar pulsations and contributed to the development of modern astrophysics.
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