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The term Star HR264 27GAM CAS refers to Gamma Cassiopeiae, a prominent star in the constellation Cassiopeia, also known by its Bayer designation γ Cassiopeiae. The designations HR264 and 27GAM CAS are catalog identifiers used in various star catalogs to reference this specific star.
Understanding the Designations
- HR264: This is the star’s listing in the Bright Star Catalogue, also known as the Harvard Revised (HR) Catalog. The catalog assigns a unique HR number to each star, with HR264 corresponding to Gamma Cassiopeiae.
- 27GAM CAS: This designation combines the Flamsteed number 27 and the Bayer designation γ (Gamma) for Cassiopeiae, indicating that it is the 27th star in the constellation Cassiopeia.
Characteristics of Gamma Cassiopeiae
Gamma Cassiopeiae is a notable star with several distinguishing features:
- Type: It is classified as a Be star, a type of B-class star known for exhibiting prominent hydrogen emission lines in its spectrum.
- Brightness: Gamma Cassiopeiae is a variable star, meaning its brightness changes over time. Its apparent magnitude varies between 2.2 and 3.4, making it sometimes the brightest star in Cassiopeia.
- Distance: The star is located approximately 550 light-years from Earth.
- Rotation: Gamma Cassiopeiae has an exceptionally high rotational velocity, estimated at around 432 kilometers per second. This rapid rotation is believed to contribute to the ejection of material, forming a surrounding disk that causes its emission lines.
Significance in Astronomy
Gamma Cassiopeiae has been extensively studied due to its unique properties:
- Variable Brightness: The variability in its brightness has made it a subject of interest for understanding stellar evolution and behavior.
- X-ray Emissions: It was one of the first stars discovered to emit X-rays, leading to insights into the mechanisms of X-ray production in massive stars.
- Prototype of Shell Stars: Gamma Cassiopeiae is considered the prototype of shell stars, which are characterized by the presence of a circumstellar disk of gas.
Observing Gamma Cassiopeiae
Located in the northern sky, Gamma Cassiopeiae is part of the distinctive “W” asterism formed by the five brightest stars in Cassiopeia. Its position and brightness make it relatively easy to observe with the naked eye, particularly in the Northern Hemisphere during autumn and winter months.
In summary, Star HR264 27GAM CAS refers to Gamma Cassiopeiae, a significant and intriguing star in the constellation Cassiopeia, known for its variable brightness, rapid rotation, and contribution to the study of stellar phenomena.