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Gamma Draconis

"Eltanin" and "Etamin" redirect here. For other uses, see Eltanin (disambiguation) and Etamin (disambiguation).
Gamma Draconis
Location of γ Draconis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 17h 56m 36.36988s[1]
Declination +51° 29′ 20.0242″[1]
Apparent magnitude (V) 2.23[2]
Characteristics
Spectral type K5 III[3]
U−B color index +1.87[2]
B−V color index +1.52[4]
Astrometry
Radial velocity (Rv)–28.19 ± 0.36[5] km/s
Proper motion (μ) RA: –8.48[1] mas/yr
Dec.: –22.79[1] mas/yr
Parallax (π)21.14 ± 0.10 mas[1]
Distance154.3 ± 0.7 ly
(47.3 ± 0.2 pc)
Absolute magnitude (MV)−1.93 ± 0.07[6]
Details[4]
Mass2.14±0.16 M☉
Radius51.8±0.26[7] R☉
Luminosity590±12[8] L☉
Surface gravity (log g)1.33±0.04[8] cgs
Temperature3,990±42 K
Metallicity [Fe/H]+0.11±0.05 dex
Rotational velocity (v sin i)4.5±0.05 km/s
Age1.3±0.25 Gyr
Other designations
Eltanin, 33 Draconis, BD +51°2282, FK5 676, HD 164058, HIP 87833, HR 6705, SAO 30653
Database references
SIMBADdata

Gamma Draconis (γ Draconis, abbreviated Gamma Dra, γ Dra), formally named Eltanin /ɛlˈteɪnɪn/,[9][10] is a star in the northern constellation of Draco. Contrary to its gamma-designation (historically third-ranked), it is the brightest object in Draco at magnitude 2.2,[1] outshining Beta Draconis by nearly half a magnitude and Alpha Draconis by over a magnitude.

Gamma Draconis is at a distance of 154.3 light-years (47.3 parsecs) from the Sun,[1] as determined by parallax measurements from the Hipparcos astrometry satellite.[11][12] In 1728, while unsuccessfully attempting to measure the parallax of this star, the English astronomer James Bradley discovered the aberration of light resulting from the relative movement of the Earth. Bradley's discovery apparently confirmed Copernicus' theory that the Earth revolved around the Sun.[13] It is drifting closer to the Solar System with a radial velocity of about –28 km/s.

In 1.5 million years, Gamma Draconis will pass within 28 light-years of Earth. For a period, if its current absolute magnitude does not change, it will be the brightest star in the night sky, nearly as bright as Sirius is at present.[13][14] It is by far the brightest star having a zenith above a point near London which led to its vaunting in these places as the "zenith star".[15] Nearby this red star to the south-southeast is Vega, a bright, well-known star in Lyra.

  1. ^ a b c d e f g Cite error: The named reference LEEUWEN was invoked but never defined (see the help page).
  2. ^ a b Oja, T. (August 1991). "UBV photometry of stars whose positions are accurately known. VI". Astronomy and Astrophysics Supplement Series. 89 (2): 415–419. Bibcode:1991A&AS...89..415O.
  3. ^ Cite error: The named reference araa11_29 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference hatzes was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference aj135_1_209 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference aaa526_A100 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference baines2021 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Soubiran2024 was invoked but never defined (see the help page).
  9. ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  10. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  11. ^ Cite error: The named reference aaa323_L49 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference GSM was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference KALER was invoked but never defined (see the help page).
  14. ^ Tomkin, Jocelyn (April 1998). "Once and Future Celestial Kings". Sky and Telescope. 95 (4): 59–63. Bibcode:1998S&T....95d..59T. – based on computations from HIPPARCOS data. (The calculations exclude stars whose distance or proper motion is uncertain.) PDF[permanent dead link]
  15. ^ Cite error: The named reference allen1963 was invoked but never defined (see the help page).

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