VV Cephei

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Double star
VV Cephei
Sonne and VV Cephei A.svg
Size comparison between the sun and VV Cephei A
Observation
dates equinox :  J2000.0 , epoch : J2000.0
AladinLite
Constellation Cepheus
Right ascension 21 h 56 m 39.1 s
declination + 63 ° 37 ′ 32.0 ″
Apparent brightness  4.91 mag
Astrometry
parallax 1.33 ± 0.20 mas
distance  4900 ly
(1500 pc )
orbit 
period 7430 days
Major semi-axis 0 ", 0120 ± 0", 0011
Individual data
Names A ; B.
Observation data:
Apparent brightness A. 5.18 likes
B. 6.66 likes
Typing:
Spectral class A. M2 Iaep
B. B6 IIe
Physical Properties:
Absolute vis.
Brightness M vis 		A. −8.0 mag
B. −6.2 mag
Absolute bol.
Brightness M bol 		A. −9.5 mag
B. −7.8 mag
Dimensions A. 25–40 or 100 M ☉
B. 20 M ☉
radius A. 1600–1900 R ☉
B. 10 R ☉
Luminosity A. 275000-575000 L ☉
B. 100,000 L ☉
Effective temperature A. 3300-3650 K
B. 10000-28000 K
Other names
and catalog entries
Bonn survey BD + 62 ° 2007
Bright Star Catalog HR 8383 [1]
Henry Draper Catalog HD 208816 [2]
SAO catalog SAO 19753 [3]
Tycho catalog TYC 4266-3252-1 [4]
Hipparcos catalog HIP 108317 [5]
Further designations: VV Cephei, IDS 21538 + 6309

VV Cephei is a binary star system located in the constellation Cepheus . The double system is about 4900 light years away from our earth. It consists of a red supergiant , VV Cephei A, who crosses the Roche line when it comes closest to its partner - VV Cephei B, a blue giant . Then matter flows from him to his blue partner. The Blue Star seems to belong to the main sequence , but it has probably already torn a lot of mass from VV Cephei A.

Surname

The first part of the name “VV” follows the rules for naming variable stars and states that VV Cephei is the fortieth variable star discovered in the constellation Cepheus. The second part of the name "Cephei" corresponds to the genitive of the Latin name of the constellation Cepheus.

Physical Properties

VV Cephei A

The supergiant VV Cephei A is one of the largest known stars in the Milky Way . It belongs to the M2 spectral class and is approximately 1,600 to 1,900 times the diameter of the sun . If it were at the position of the sun, then its greatest extent would even include the orbit of Saturn . In terms of volume, the sun would fit about 5.3 billion times into VV Cephei A. Its brightness is approximately 275,000 to 575,000 times the luminosity of the sun. The mass of the star is estimated by astronomers on the basis of the movement of bodies in its orbit at a mass of ~ 5 * 10 31 to ~ 2 * 10 32 kg, which would be 25 to 100 times that of the sun. On the other hand, a calculation based on its brightness results in between 25 and 40 solar masses.

VV Cephei B

VV Cephei B is a main series blue giant . It is a B-star with ten times the solar diameter and 100,000 times the solar brightness. One revolution of the system takes 7430 days (20.3 years). Its eclipse lasts about 650 days; his last occultation by VV Cephei A took place from August 4, 2017 to May 16, 2019. The apparent brightness of the system fell from 4.8 to 5.4 mag.

Eclipsing star

The light curve shows almost no change, while VV Cephei B (blue) passes the supergiant VV Cephei A:
VV Cephei eclipsing binary B front (german) .png

The light curve, however, drops suddenly as soon as VV Cephei B passes behind VV Cephei A:
VV Cephei eclipsing binary B behind (german) .png

See also

Web links

Commons : VV Cephei  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c SIMBAD Query Result: V * VV Cep - Eclipsing binary of Algol type. Center de Données astronomiques de Strasbourg, accessed on November 10, 2008 (English).
  2. ↑ Dr. Thomas G. Franke, William B. Albrecht, Terri Osland: The Brightest Stars. Retrieved September 29, 2008 .
  3. ↑ Heaven's Almanac 2017 . In: Ronald Stoyan (Ed.): Adventure Astronomy . Special issue 2 / 2017. Oculum-Verlag, October 2016, ISSN  2366-3944 , p. 31 .