Delta Doradus

Delta Doradus
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Dorado
Right ascension 05h 44m 46.37811s[1]
Declination −65° 44′ 07.9011″[1]
Apparent magnitude (V) +4.34[2]
Characteristics
Spectral type A7 V[3]
U−B color index +0.11[2]
B−V color index +0.22[2]
Astrometry
Radial velocity (Rv)−8.3±0.8[4] km/s
Proper motion (μ) RA: −28.91[1] mas/yr
Dec.: +5.17[1] mas/yr
Parallax (π)21.80 ± 0.14 mas[1]
Distance149.6 ± 1.0 ly
(45.9 ± 0.3 pc)
Absolute magnitude (MV)+1.03[5]
Details
Mass1.85[6] M☉
Radius2.1[7] R☉
Luminosity29[8] L☉
Surface gravity (log g)3.89[6] cgs
Temperature7,828±266[6] K
Metallicity [Fe/H]−0.40[9] dex
Rotational velocity (v sin i)172[3] km/s
Age940[6] Myr
Other designations
δ Dor, CPD−65° 496, FK5 1154, HD 39014, HIP 27100, HR 2015, SAO 249346[10]
Database references
SIMBADdata

δ Doradus (often Latinised to Delta Doradus, abbreviated to δ Dor or delta Dor) is a star in the southern constellation of Dorado. Based upon an annual parallax shift of 21.80 mas as seen from Earth, it is located around 150 light years from the Sun. The star is visible to the naked eye with an apparent visual magnitude of +4.34.[2]

This is an A-type main sequence star with a stellar classification of A7 V.[3] The star is spinning rapidly with a projected rotational velocity of 172 km/s.[3] This is giving the star an oblate shape with an equatorial bulge that is 12% larger than the polar radius.[11] Although A-type stars are not expected to harbor a magnetic dynamo needed to power X-ray emission, an X-ray flux of 3.6×1027 erg/s has been detected at these coordinates. This may indicate that the star has an unseen companion.[12] δ Doradus displays an infrared excess suggesting it may be a Vega-like star with an orbiting debris disk.[9]

Currently this star is the Moon's south pole star, which occurs once every 18.6 years.[13] The pole star status changes periodically, because of the precession of the Moon's rotational axis. When δ Doradus is the pole star, it is better aligned than Earth's Polaris (α Ursae Minoris), but much fainter. It is also the south pole star of Jupiter.[citation needed]

  1. ^ a b c d e Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Mermilliod1986 was invoked but never defined (see the help page).
  3. ^ a b c d Cite error: The named reference Royer2007 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference deBruijne2012 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference David2015 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference PasinettiFracassini2001 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Mcdonald2012 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Saffe2008 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference vanBelle2012 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Schroeder2007 was invoked but never defined (see the help page).
  13. ^ Patrick Moore (1983), The Guinness Book of Astronomy Facts & Feats, p. 29, In 1968 the north pole star of the Moon was Omega Draconis; by 1977 it was 36 Draconis. The south pole star is Delta Doradus.