Eta Apodis

  1. Home
  2. Wiki
η Apodis
Location of η Apodis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Apus[1]
Right ascension 14h 18m 13.89590s[2]
Declination −81° 00′ 27.9306″[2]
Apparent magnitude (V) +4.89[3]
Characteristics
Spectral type A2MA7-F2[4] or A2(m) CrEu[5]
U−B color index +0.11[6]
B−V color index +0.25[6]
Variable type α2 CVn[7]
Astrometry
Radial velocity (Rv)−9.4[3] km/s
Proper motion (μ) RA: −19.981 mas/yr[2]
Dec.: −65.222 mas/yr[2]
Parallax (π)22.9229±0.1180 mas[2]
Distance142.3 ± 0.7 ly
(43.6 ± 0.2 pc)
Absolute magnitude (MV)+1.76[1]
Details
Mass1.77[8] M☉
Radius2.13[8] R☉
Luminosity15.5[8] L☉
Temperature7,860±20[8] K
Rotational velocity (v sin i)17.2±0.3[9] km/s
Age250±200[8] Myr
Other designations
CD−80 706, FK5 3129, HD 123998, HIP 69896, HR 5303, SAO 258693[10]
Database references
SIMBADdata

Eta Apodis is a star in the southern circumpolar constellation Apus. Its identifier is a Bayer designation that is Latinized from η Apodis, and abbreviated Eta Aps or η Aps, respectively. Based upon parallax measurements from Gaia Data Release 3, it is 142 light-years (44 parsecs) from Earth. It is drifting closer with a heliocentric radial velocity of −9 km/s.[3] With an apparent visual magnitude of +4.9, it can be viewed with the naked eye from the southern hemisphere.

Properties

[edit]

This star has about 1.77 times the mass of the Sun and 2.13 times the Sun's radius. It is radiating 15.5 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 7,860 K.[8] Eta Apodis is a young star with an age of about 250 million years,[8] and is spinning with a projected rotational velocity of 17 km/s.[9]

The stellar classification of Eta Apodis shows this to be an Am star, which means the spectrum shows chemically peculiarities. In particular, it is an A2-type star showing an excess of the elements chromium and europium. The spectrum displays magnetically-induced features indicating an estimated surface field strength of roughly 360 G.[5] Data from the TESS satellite found it to be an Alpha2 Canum Venaticorum-type variable star,[7] consistent with its magnetic and chemical properties.[11] The variability range is only a thousandth of a magnitude.[7]

Based upon observations with the Spitzer Space Telescope, this system is emitting an excess of 24 μm infrared radiation. This may be caused by a debris disk of dust orbiting at a distance of more than 31 astronomical units from the star.[8]

Naming

[edit]

In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, 異雀 (Yì Què), meaning Exotic Bird, refers to an asterism consisting of η Apodis, ζ Apodis, ι Apodis, β Apodis, γ Apodis, δ1 Apodis, α Apodis and ε Apodis. Consequently, η Apodis itself is known as 異雀七 (Yì Què qī, English: the Seventh Star of Exotic Bird.)[12]

References

[edit]
  1. ^ a b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
  2. ^ a b c d Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b c Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
  4. ^ Houk, Nancy (1979), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 1, Ann Arbor, Michigan: Dept. of Astronomy, University of Michigan, Bibcode:1978mcts.book.....H
  5. ^ a b Bychkov, V. D.; Bychkova, L. V.; Madej, J. (August 2003), "Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars", Astronomy and Astrophysics, 407 (2): 631–642, arXiv:astro-ph/0307356, Bibcode:2003A&A...407..631B, doi:10.1051/0004-6361:20030741, S2CID 14184105
  6. ^ a b Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
  7. ^ a b c "VSX : Detail for eta Aps". AAVSO. Retrieved 2023-10-16.
  8. ^ a b c d e f g h Plavchan, Peter; et al. (June 2009), "New Debris Disks Around Young, Low-Mass Stars Discovered with the Spitzer Space Telescope", The Astrophysical Journal, 698 (2): 1068–1094, arXiv:0904.0819, Bibcode:2009ApJ...698.1068P, doi:10.1088/0004-637X/698/2/1068, S2CID 51417657
  9. ^ a b Díaz, C. G.; et al. (July 2011), "Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum", Astronomy & Astrophysics, 531: A143, arXiv:1012.4858, Bibcode:2011A&A...531A.143D, doi:10.1051/0004-6361/201016386, S2CID 119286673
  10. ^ "eta Aps -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-07-08.
  11. ^ "VSX Variability Types. ACV". AAVSO. Retrieved 2025-03-11.
  12. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 29 日 Archived 2011-05-22 at the Wayback Machine