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Omicron Draconis

Omicron Draconis
Draco constellation map.svg
Red circle.svg

Location of ο Dra (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 18h 51m 12.09530s
Declination +59° 23′ 18.0627″
Apparent magnitude (V) 4.65
Characteristics
Spectral type G9III
U−B color index +1.19
Variable type RS CVn
Astrometry
Radial velocity (Rv) −19.52 km/s
Proper motion (μ) RA: 77.47 mas/yr
Dec.: 25.37 mas/yr
Parallax (π) 9.54 ± 0.21mas
Distance 106.8pc
Absolute magnitude (MV) −0.344
Orbit
Primary ο Dra A
Companion ο Dra B
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 M
Radius 25.1 R
Luminosity 220 L
Surface gravity (log g) 1.769 cgs
Temperature 4400 K
Metallicity [Fe/H] −0.5 dex
Rotation 79
Rotational velocity (v sin i) 20.0 km/s
Age 3.0 Gyr
ο Dra B
Mass 0.99 M
Radius 1.0 R
Luminosity 1.3 L
Surface gravity (log g) 4.43 cgs
Temperature 6,000 K
Other designations
Omicron Draconis, 47 Draconis, HR 7125, HD 175306, HIP 92512, BD+59°1925
Database references
SIMBAD data

Omicron Draconis (ο Dra, ο Draconis) is a giant star in the constellation Draco located 322.93 light years from the Earth. It has a radius of 30 solar radii, and a luminosity of 269 suns. Its path in the night sky is circumpolar above the ecliptic, meaning the star never rises or sets when viewed in the night sky from certain positions in the northern hemisphere.

Omicron Draconis can be considered the north pole star of Mercury, as it is the closest star to Mercury's north celestial pole.

This is a single-lined spectroscopic binary system, but the secondary has been detected using interferometry. It is a RS Canum Venaticorum variable system with eclipses. The total amplitude of variation is only about a thousandth of a magnitude. 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.


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Wikipedia

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