Chi Cygni

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Chi Cygni
Red Giant Chi Cygni.png
Chi Cygni. How the star would appear at nearly 48 astronomical units.
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 Variable Star of Mira Cet type
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[1] R
Luminosity 7250[1] L
Temperature 3000[1] K
Rotation 470 days
Other designations
V* chi Cyg, chi Cyg, HD 187796, BD+32° 3593, HIP 97629, HR 7564, SAO 68943.
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 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 345 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,

  1. When at its full brightness, it undergoes no perceptible change for a fortnight.
  2. 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.
  3. 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[edit]

  1. ^ a b c Hinkle et al.; Hall, D. N. B.; Ridgway, S. T. (1982). "Time series infrared spectroscopy of the mira variable Chi Cygni". The Astrophysical Journal, Part 1 252: 697–714. Bibcode:1982ApJ...252..697H. doi:10.1086/159596. 

Sources[edit]

  • Robert Burnham Jr.: Burnham's Celestial Handbook, Volume Two, p. 762

External links[edit]