18 Draconis

18 Draconis

18 Draconis in optical light
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 16h 40m 55.11952s[1]
Declination +64° 35′ 20.5824″[1]
Apparent magnitude (V) 4.84[2]
Characteristics
Spectral type K0 III CN−0.5 CH−2 Ca1[3]
B−V color index 1.212±0.003[2]
Astrometry
Radial velocity (Rv)−1.37±0.09[4] km/s
Proper motion (μ) RA: −0.599[1] mas/yr
Dec.: −17.436[1] mas/yr
Parallax (π)4.5045 ± 0.1730 mas[1]
Distance720 ± 30 ly
(222 ± 9 pc)
Absolute magnitude (MV)−1.92[2]
Details[5]
Mass3.81±0.38 M☉
Radius46.83±1.74 R☉
Luminosity786.7±56.3 L☉
Surface gravity (log g)1.69±0.06 cgs
Temperature4,471±23 K
Metallicity [Fe/H]−0.13±0.10 dex
Age280±80 Myr
Other designations
g Dra, 18 Dra, BD+64° 1145, FK5 3326, HD 151101, HIP 81660, HR 6223, SAO 17188[6]
Database references
SIMBADdata

18 Draconis is a likely binary star[7] system in the northern circumpolar constellation of Draco. With an apparent visual magnitude of 4.84,[2] it is just bright enough to be faintly visible to the naked eye. The distance to this system, as estimated from an annual parallax shift of 4.5 mas,[1] is roughly 720 light years. It is moving closer to the Sun with a heliocentric radial velocity of −1.4 km/s,[4] and is a probable member of the Sirius stream of co-moving stars.[8]

The visible component has a stellar classification of K0 III CN−0.5 CH−2 Ca1,[3] indicating it is an evolved K-type giant star with some abundance peculiarities in its atmosphere. At the age of around 280 million years, it is most likely (99% chance) on the horizontal branch.[5] It is a barium star, which suggests it may have a degenerate white dwarf companion from which it accreted materials during an earlier stage of its evolution.[9][7] 18 Dra has an estimated 3.8 times the mass of the Sun and has expanded to 47 times the Sun's radius. The star is radiating 787 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,471 K.[5]

  1. ^ a b c d e f Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference perkins1989 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference deBruijne2012 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference reffert2015 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Famaey2005 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference gomez was invoked but never defined (see the help page).