Omicron Draconis

Short description: Variable star in the constellation Draco

Omicron Draconis

Location of ο Dra (circled)

Observation data
Equinox J2000.0]] (ICRS)
Constellation | Draco
Right ascension |  18h 51m 12.09530s[1]
Declination | +59° 23′ 18.0627″[1]
Apparent magnitude (V) | 4.65[2]
Characteristics
Spectral type | G9III[3]
U−B color index | +1.19[2]
Variable type | RS CVn \+ eclipsing[4]
Astrometry
Radial velocity (Rv)| −19.52[5] km/s
Proper motion (μ)|  RA: 77.47[1] mas/yr
Dec.: 25.37[1] mas/yr
Parallax (π)| 9.54 ± 0.21[1] mas
Distance| 106.8[4] pc
Absolute magnitude (MV)| −0.344[6]
Orbit[4]
Period (P)| 138.444 ± 0.003 days
Semi-major axis (a)| 6.51 ± 0.03″
Eccentricity (e)| 0.158 ± 0.003
Inclination (i)| 89.6 ± 0.3°
Longitude of the node (Ω)| 22.9 ± 0.2°
Periastron epoch (T)| 2454983.0 ± 0.2
Argument of periastron (ω)
(secondary)| 293.0 ± 0.6°
Semi-amplitude (K1)
(primary)| 23.42 ± 0.05 km/s
Semi-amplitude (K2)
(secondary)| 32.0 ± 0.4 km/s
Details
ο Dra A
Mass| 1.35[4] M☉
Radius| 25.1[4] R☉
Luminosity| 220[4] L☉
Surface gravity (log g)| 1.769[4] cgs
Temperature| 4400[7] K
Metallicity [Fe/H]| −0.5[3] dex
Rotation| 79[4]
Rotational velocity (v sin i)| 20.0[6] km/s
Age| 3.0[4] Gyr
ο Dra B
Mass| 0.99[4] M☉
Radius| 1.0[4] R☉
Luminosity| 1.3[4] L☉
Surface gravity (log g)| 4.43[4] cgs
Temperature| 6,000[4] K
Other designations

Omicron Draconis, 47 Draconis, HR 7125, HD 175306, HIP 92512, BD+59°1925

Database references
SIMBAD| data

Omicron Draconis (Latinised as ο Draconis, abbreviated to ο Dra) is a giant star in the constellation Draco located 322.93 light years from the Earth. Its path in the night sky is circumpolar for latitudes greater than 31o north, meaning the star never rises or sets when viewed in the night sky.

A visual band light curve for Omicron Draconis, adapted from Roettenbacher et al. (2015)[4]

This is a single-lined spectroscopic binary system,[7] but the secondary has been detected using interferometry. It is an RS Canum Venaticorum variable system with eclipses. The total amplitude of variation is only a few hundredths of a magnitude.[8][4] The secondary star is similar to the Sun, presumably a main sequence star, while the primary is a giant star 25 times larger than the Sun and two hundred times more luminous.

## Identities as pole star

Omicron Draconis can be considered the north pole star of Mercury, as it is the closest star to Mercury's north celestial pole.[9] In addition to that, this star is currently the Moon's north pole star, which occurs once every 18.6 years.[10] The pole star status changes periodically, because of the precession of the Moon's rotational axis.

## References

1. ↑ 1.0 1.1 1.2 1.3 1.4 Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V.
2. ↑ 2.0 2.1 Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven. Bibcode: 1991bsc..book.....H.
3. ↑ 3.0 3.1 Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series 71: 245. doi:10.1086/191373. Bibcode: 1989ApJS...71..245K.
4. ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 Roettenbacher, Rachael M.; Monnier, John D.; Fekel, Francis C.; Henry, Gregory W.; Korhonen, Heidi; Latham, David W.; Muterspaugh, Matthew W.; Williamson, Michael H. et al. (2015). "Detecting the Companions and Ellipsoidal Variations of RS CVn Primaries. II. O Draconis, a Candidate for Recent Low-mass Companion Ingestion". The Astrophysical Journal 809 (2): 159. doi:10.1088/0004-637X/809/2/159. Bibcode: 2015ApJ...809..159R.
5. ↑ Karataș, Yüksel; Bilir, Selçuk; Eker, Zeki; Demircan, Osman; Liebert, James; Hawley, Suzanne L.; Fraser, Oliver J.; Covey, Kevin R. et al. (2004). "Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution". Monthly Notices of the Royal Astronomical Society 349 (3): 1069–1092. doi:10.1111/j.1365-2966.2004.07588.x. Bibcode: 2004MNRAS.349.1069K.
6. ↑ 6.0 6.1 Böhm-Vitense, Erika et al. (December 2000), "Ultraviolet Emission Lines in BA and Non-BA Giants", The Astrophysical Journal 545 (2): 992–999, doi:10.1086/317850, Bibcode: 2000ApJ...545..992B.
7. ↑ 7.0 7.1 Pourbaix, D.; Boffin, H. M. J. (February 2003), "Reprocessing the Hipparcos Intermediate Astrometric Data of spectroscopic binaries. II. Systems with a giant component", Astronomy and Astrophysics 398 (3): 1163–1177, doi:10.1051/0004-6361:20021736, Bibcode: 2003A&A...398.1163P
8. ↑ "omi Dra". AAVSO. https://www.aavso.org/vsx/index.php?view=detail.top&oid=13951.
9. ↑ Sharrah, Paul C. (1975). "Pole Stars of Other Planets" (pdf). Arkansas Academy of Sciences Proceedings XXIX: 62–63. https://scholarworks.uark.edu/cgi/viewcontent.cgi?article=2873&context=jaas.
10. ↑ 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."

## External links

* 2004\. Starry Night Pro, Version 5.8.4. Imaginova. ISBN 978-0-07-333666-4. www.starrynight.com

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Draco constellation

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Other|

* 3C 249.1
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