Chi Cygni
 Location of χ Cygni (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 50m 33.922s |
| Declination | +32° 54′ 50.61″ |
| Apparent magnitude (V) | 3.3 - 14.2 |
| Characteristics | |
| Spectral type | S6III |
| B−V color index | 1.55 |
| Variable type | Mira[1] |
| Astrometry | |
| Radial velocity (Rv) | -1.9 km/s |
| Proper motion (μ) | RA: -20.16 mas/yr Dec.: -38.34 mas/yr |
| Parallax (π) | 5.53 ± 1.10 mas |
| Distance | approx. 600 ly (approx. 180 pc) |
| Absolute magnitude (MV) | −3 - 7.9 |
| Details | |
| Radius | 316[2] R☉ |
| Luminosity | 7250[2] L☉ |
| Temperature | 3000[2] K |
| Rotation | 470 days |
| Other designations | |
| Database references | |
| SIMBAD | data |
Chi Cygni (χ Cyg, χ Cygni) is a variable star of the Mira type in the constellation Cygnus.
Chi Cygni shows one of the largest variations in apparent magnitude known. Typically it brightens and fades from 5th to 13th magnitude. The average period of this brightness fluctuation is 407 days. Observed extremes were 3.3 and 14.3 respectively. Thus Chi Cygni is visible at its minimum only with telescopes larger than 30 centimeters, while at maximum brightness is easily visible to the naked eye. Its distance is approximately 600 light years. The astronomer Gottfried Kirch discovered its variability in 1686.
Thomas Dick, LL.D, writes:
"The period of this star has been settled by Maraldi and Cassini at 405 days; but from a mean of the observations of Mr. Pigot, it appears to be only 392, or at most 396-7/8 days.
"The particulars relating to it are,
- When at its full brightness, it undergoes no perceptible change for a fortnight.
- It is about three and a half months in increasing from the eleventh magnitude to its full brightness, and the same in decreasing; for which reason it may be considered as invisible during six months.
- It does not always attain the same degree of lustre, being sometimes of the 5th and sometimes of the seventh magnitude.
"It is situated in the neck [of the Swan constellation], and nearly equi-distant from Beta and Gamma, and south by west from Deneb, at the distance of about twelve degrees, and is marked Chi."
References
Sources
- Robert Burnham Jr.: Burnham's Celestial Handbook, Volume Two, p. 762
