Epoch J2000.0 Equinox J2000.0
|Apparent magnitude (V)||+4.6 - +5.2|
|U−B color index||+1.16|
|B−V color index||+1.0 - +1.7|
|Radial velocity (Rv)||−58 km/s|
|Proper motion (μ)||RA: −2.94 mas/yr
Dec.: −3.09 mas/yr
|Parallax (π)||0.73 ± 0.25 mas|
|Absolute magnitude (MV)||−8.6 (variable)|
|Mass||11 (decreasing) M☉|
|Radius||400 -900 R☉|
|Luminosity||200.000 - 400,000 L☉|
|Temperature||4,000-8,000 (increasing) K|
V509 Cassiopeiae is yellow hypergiant with a G-type and an apparent magnitude that has varied from below +6 in historical times to a peak of +4.3 and now around +5.2. It is around 4,500 light years from Earth. It is classified as a semiregular variable star of type SRd. Characteristic periods around a year are reported imposed on the slower secular variations. It is undergoing strong mass loss as part of its rapid evolution. It has recently passed through the yellow evolutionary void by ejecting around a solar mass of material in less than 50 years.
A hot main sequence companion (B1V) was described in 1978 on the basis of a colour excess in the ultraviolet but has not been reported since.
This type of star has evolved from an initial mass of 25-40 times the sun to a red hypergiant and is now shedding its remaining outer layers in a series of dramatic explosions, progressively increasing in temperature. It may become a blue supergiant or luminous blue variable before declining in luminosity as a late type Wolf–Rayet star, but is expected to explode as a supernova before that point.
- h. Nieuwenhuijzen, H.; c. De Jager, C.; i. Kolka, I.; g. Israelian, G.; a. Lobel, A.; e. Zsoldos, E.; a. Maeder, A.; g. Meynet, G. (2012). "The hypergiant HR 8752 evolving through the yellow evolutionary void". Astronomy & Astrophysics 546: A105. Bibcode:2012A&A...546A.105N. doi:10.1051/0004-6361/201117166.
- Bibcode: 1992A&A...263..123P
- Bibcode: 1978A&A....70L..53S