Sigma Ceti

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Sigma Ceti
Observation data
ICRS
)
Constellation Cetus
σ Cet A
Right ascension 02h 32m 05.22884s[1]
Declination −15° 14′ 40.8278″[1]
Apparent magnitude (V) 4.75[2]
σ Cet B
Right ascension 02h 31m 42.47292s[3]
Declination −15° 16′ 24.4275″[3]
Apparent magnitude (V) 8.74[2]
Characteristics
σ Cet A
Spectral type F5 V[4] or F4 IV[5]
U−B color index −0.03[6]
B−V color index +0.45[6]
σ Cet B
Spectral type K2.5V[2]
Distance
87.70 ± 0.04 ly
(26.89 ± 0.01 pc)
Absolute magnitude (MV)+6.48[7]
Semi-amplitude
(K1)
(primary)		7.56±0.25 km/s
Position (relative to σ Cet A)[2]
Componentσ Cet B
Projected separation
9,800[b] AU
Details
σ Cet Aa
Gyr
σ Cet Ab
Mass0.70[2] M☉
σ Cet B
Mass0.77[2] M☉
Radius0.698±0.048[11] R☉
Luminosity0.262±0.008[11] L☉
Temperature4,935±145[11] K
HR 740, SAO 148445[12]
B: HIP 11759, HD 15767, BD−15°447, TIC 66574369, SAO 148443[13]
Database references
SIMBADσ Cet A
σ Cet B

Sigma Ceti (σ Ceti) is a

light years from the Sun
.

Characteristics

This is a hierarchical triple system. The inner pair contains the primary, component Aa, and the secondary, component Ab. They form a

periastron (closest distance between stars) was in 2015.[2]

The primary, component Aa, appears to be a normal

subgiant star. It is estimated to have 145% of the Sun's mass[2] and around 211% of the radius of the Sun.[8] With an age of about 2.1 billion years,[10] it is radiating seven times the solar luminosity from its outer atmosphere[8] at an effective temperature of 6,527 K.[9]

The secondary, Sigma Ceti Ab, is 3.89 magnitudes fainter than the primary in the I-band. Little is known about it. Its mass is estimated at 70% the mass of the Sun.[2]

The outer component is the

K-dwarf star, with a faint apparent magnitude of 8.74. It has 77% the mass of the Sun[2] and 70% of the Sun's radius. It radiates 0.26 solar luminosities from its photosphere at an effective temperature of about 5,000 K.[11]

Name

This star, along with π Cet, ε Cet and ρ Cet, was Al Sufi's Al Sadr al Ḳaiṭos, the Whale's Breast.[14]

According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al Sadr al Ḳaiṭos were the title for four stars :ρ Cet as Al Sadr al Ḳaiṭos I, this star (σ Cet) as Al Sadr al Ḳaiṭos II, ε Cet as Al Sadr al Ḳaiṭos III and π Cet as Al Sadr al Ḳaiṭos IV[15]

Notes

  1. arcseconds and the separation of 0.3616 arcseconds. 0.3616" / 0.03719" = 9.65 AU
    .
  2. arcseconds and the separation of 345 arcseconds. 345" / 0.03719" = 9,300 AU
    .

References

  1. ^
    S2CID 18759600
    .
  2. ^
    doi:10.3847/1538-3881/ada3c6
    .
  3. ^
    S2CID 244398875
    . Gaia DR3 record for this source at VizieR.
  4. ^
    doi:10.1093/pasj/57.1.13
    .
  5. ^
    doi:10.1086/111786
    .
  6. ^
    Bibcode:1986EgUBV........0M
    .
  7. doi:10.3847/1538-3881/ac082a
    .
  8. ^
    ISSN 0067-0049. Sigma Ceti Aa's database entry at VizieR
    .
  9. ^
    S2CID 54940439
    .
  10. ^
    S2CID 33401607
    .
  11. ^
    ISSN 0004-6256
    .
  12. ^ "* sig Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-02-09.
  13. ^ "HD 15767". SIMBAD. Centre de données astronomiques de Strasbourg.
  14. ISBN 978-0-486-21079-7
    . Retrieved 2010-12-12.
  15. ^ Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
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