Caph

from Wikipedia, the free encyclopedia
Star
caph
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Cassiopeia
Right ascension 00 h 09 m 10.69 s
declination + 59 ° 08 ′ 59.2 ″
Apparent brightness 2.27var mag
Typing
B − V color index 0.34 
U − B color index 0.11 
R − I index 0.20 
Spectral class F2 III-IV
Variable star type δ Scuti star 
Astrometry
Radial velocity 4.3 ± 0.8 km / s
parallax 59.58 ± 0.38  mas
distance 54.7 ± 0.4  ly
16.8 ± 0.1  pc  
Visual absolute brightness M vis 1.14 mag
Proper movement 
Rec. Share: 523.50 ± 0.32  mas / a
Dec. portion: −179.77 ± 0.31  mas / a
Physical Properties
Dimensions 1.9  M ☉
radius 3.1 - 3.8  R ☉
Luminosity

≈ 21  L ☉

Effective temperature 6,200 - 7,200  K
Metallicity [Fe / H] 0.03
Rotation time 0.9 d
Age ≈ 1.2 billion  a
Other names
and catalog entries
Bayer name β Cassiopeiae
Flamsteed name 11 Cassiopeiae
Bonn survey BD + 58 ° 3
Bright Star Catalog HR 21 [1]
Henry Draper Catalog HD 432 [2]
Gliese catalog FY 8 [3]
Hipparcos catalog HIP 746 [4]
SAO catalog SAO 21133 [5]
Tycho catalog TYC 3664-1985-1 [6]
2MASS catalog 2MASS J00091071 + 5908591 [7]
Other names FK5 2; ADS 107; CCDM 00092 + 5909; GJ 8; IRAS 00065 + 5852; LFT 15; LHS 1027; LTT 10046

Caph ( Arabic كف, DMG Kaf  'palm') or β Cassiopeiae ( Beta Cassiopeiae , β Cas for short ) is a star in the constellation Cassiopeia . Caph has an apparent magnitude of 2.27 mag, belongs to the spectral class F2 III – IV and is 55 light years away from us.

properties

Caph has a mass of around 2 M ⊙ . The axis of rotation is inclined by about 20 ° in relation to our line of sight, which means that we are mainly looking at the star's pole. The star rotates very quickly and has a flattening of 1: 4.2, ie the radius at the equator is approx. 24% larger than at the poles (equatorial radius ≈ 3.8 R ⊙ , pole radius ≈ 3.1 R ⊙ ). Due to the gravity darkening , the effective temperature at the equator is approx. 6,200 K and at the poles approx. 7,200 K. The projected equatorial rotation speed is v sin i ≈ 72 km / s, which corresponds to an inclination of the axis of rotation of i = 19, 9 ° corresponds to a true rotational speed at the equator of v ≈ 213 km / s. This is 92% of the critical speed at which the star at the equator would hurl matter into space. The equator radius mentioned above results in 1.1 revolutions / day, or in other words, a rotation period of 0.9 days.

Caph is also a variable star from the δ-Scuti type . The light change is monoperiodic, the period is 0.101 036 676 days. The pulsation mode is not known, but there is some evidence that the star pulsates nonradially and in the second overtone. The V brightness fluctuates around 0.04 mag (2.25 - 2.29 mag); Caph is thus a low-amplitude δ Scuti star ( LADS for short ).

Previously, Caph was classified as a spectroscopic binary star with an orbital period of 27 days. Later investigations did not confirm a spectroscopic companion; Caph is now considered a single star.

Timing

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

Since Caph is very close to the Kolur with 0 ° right ascension - the "prime meridian" of the sky - it is well suited as a "clock hand" to determine sidereal time . He stands:

  • over the North Star , it is midnight
  • west (left) of the North Star, it is 6 o'clock,
  • under the North Star , it is 12 o'clock
  • east (right) of the North Star, it is 6 p.m.

The sidereal time can then be converted into solar time (time) with the help of the date:

,

where M is the month and T is the day of the current date. During summer time you have to add an hour and - in Germany - up to 30 minutes, depending on how far west of the 15th meridian you are.

See also

Web links

Individual evidence

  1. ^ A b c Floor van Leeuwen: Hipparcos, the New Reduction . VizieR data catalog I / 311 (published electronically). 2008, bibcode : 2008yCat.1311 .... 0V . VizieR catalog entry .
  2. ↑ a b c d Dorrit Hoffleit, Wayne H. Warren Jr .: Bright Star Catalog, 5th Revised Ed. VizieR data catalog V / 50 (published electronically). 1995, bibcode : 1995yCat.5050 .... 0H . VizieR catalog entry .
  3. ^ William W. Morgan , Philip C. Keenan : Spectral classification . In: Annual Review of Astronomy and Astrophysics . Vol. 11, 1973, p. 33, bibcode : 1973ARA & A..11 ... 29M , doi: 10.1146 / annurev.aa.11.090173.000333 .
  4. ↑ George A. Gontcharov: Pulkovo radial velocities for 35493 HIP stars . VizieR data catalog III / 252 (published electronically). 2007, bibcode : 2007yCat.3252 .... 0G . VizieR catalog entry .
  5. ↑ Derived from parallax ( π = 59.58 ± 0.38 mas, van Leeuwen 2007).
  6. ↑ Calculated from the apparent brightness m V and parallax π (in arc seconds) according to m V - 5 ∙ lg (1 / π) + 5 .
  7. ↑ a b c d e f g Xiao Che et al. : Colder and Hotter: Interferometric Imaging of β Cassiopeiae and α Leonis . In: The Astrophysical Journal . Vol. 732, Ausg. 2, 2011, Art.-ID 68, pp. 4–5, bibcode : 2011ApJ ... 732 ... 68C , doi: 10.1088 / 0004-637X / 732/2/68 , arxiv : 1105.0740 .
  8. ↑ Birgitta Nordström et al. : Geneva-Copenhagen Survey of Solar neighborhood . VizieR data catalog V / 117A (published electronically). 2004–2008, bibcode : 2008yCat.5117 .... 0N . VizieR catalog entry .
  9. ↑ a b Guillaume Guiglion et al. : Understanding the dynamical structure of pulsating stars: The Baade-Wesselink projection factor of the δ Scuti stars AI Velorum and β Cassiopeiae . In: Astronomy & Astrophysics . Vol. 550, 2013, Art.-ID L10, bibcode : 2013A & A ... 550L..10G , doi: 10.1051 / 0004-6361 / 201220780 , arxiv : 1301.2475 .
  10. ↑ a b E. Riboni, E. Poretti, G. Galli: The long-term behavior of the photometric variability of β Cassiopeiae . In: Astronomy and Astrophysics Supplement Series . Vol. 108, 1994, pp. 57-60, bibcode : 1994A & AS..108 ... 55R . Information on the brightness is taken from FIGS. 2 and 3.
  11. ↑ Eloy Rodriguez et al. : Stromgren photometry of the low amplitude delta Scuti star beta Cassiopeiae . In: Astronomy and Astrophysics Supplement Series , Vol. 96, 1992, p. 432, bibcode : 1992A & AS ... 96..429R .
  12. ↑ Helmut A. Abt: The Frequency of Binaries among Normal A-Type Stars . In: Astrophysical Journal Supplement . Vol. 11, 1965, p. 440, bibcode : 1965ApJS ... 11..429A , doi: 10.1086 / 190120 .
  13. ↑ Stephenson Yang et al. : Radial velocity variations of the δ Scuti variable β Cassiopeiae . In: Publications of the Astronomical Society of the Pacific . Vol. 94, 1982, p. 320, bibcode : 1982PASP ... 94..317Y , doi: 10.1086 / 130982 .