42 Draconis (abbreviated 42 Dra), formally named Fafnir (/ˈfɑːvnər/ or /ˈfɑːfnɪər/),[3][4] is a 5th magnitude K-type giant star located approximately 315 light years away in the constellation of Draco. As of 2009, an extrasolar planet (designated 42 Draconis b, later named Orbitar) is thought to be orbiting the star.

42 Draconis

42 Draconis in optical light
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Draco
Right ascension	18h 25m 59.13734s[1]
Declination	+65° 33′ 48.5288″[1]
Apparent magnitude (V)	4.82[2]
Characteristics
Spectral type	K1.5 III[2]
B−V color index	1.187
Astrometry
Radial velocity (Rv)	32.17 ± 0.20 km/s
Proper motion (μ)	RA: 105.83 ± 0.21[1] mas/yr Dec.: -27.24 ± 0.28[1] mas/yr
Parallax (π)	10.36 ± 0.20 mas[1]
Distance	315 ± 6 ly (97 ± 2 pc)
Absolute magnitude (MV)	–0.108
Details[2]
Mass	0.879±0.050 M☉
Radius	21.76±0.43 R☉
Luminosity	142.55±5.77 L☉
Surface gravity (log g)	2.1±0.54 cgs
Temperature	4,280±16 K
Metallicity [Fe/H]	−0.5 dex
Age	13.19±1.92 Gyr
Other designations
Fafnir, BD+65° 1271, GC 25212, HD 170693, HIP 90344, HR 6945, SAO 17888, PPM 20916, GCRV 10941
Database references
SIMBAD	data
Exoplanet Archive	data
Extrasolar Planets Encyclopaedia	data

Of spectral type K1.5III, the star has a mass similar to the Sun but with a radius 22 times greater. It is a metal-poor star with metallicity as low as 35% that of the Sun and its age is 9.49 billion years. It is the northern pole star of Venus.[5]

Nomenclature

42 Draconis is the star's Flamsteed designation. Following its discovery the planet was designated 42 Draconis b. In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.[6] The process involved public nomination and voting for the new names.[7] In December 2015, the IAU announced the winning names were Fafnir for this star and Orbitar for its planet.[8]

The winning names were submitted by the Brevard Astronomical Society of Brevard County, Florida, United States.[9] Fafnir was a Norse mythological dwarf who turned into a dragon, it is also the name of a fictional planet in Larry Niven's known space universe of similar description, ('Draco' is Latin for 'dragon'); Orbitar is a contrived word paying homage to the space launch and orbital operations of NASA.[10]

In 2016, the IAU organized a Working Group on Star Names (WGSN)[11] to catalog and standardize proper names for stars. In its first bulletin of July 2016,[12] the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.[4]

Planetary system

42 Draconis b was discovered in 2009. It is an example of a super-Jupiter.

See also

• HD 139357
• Iota Draconis
• Lists of exoplanets

References

External links

• Jean Schneider (2011). "Notes for star 42 Dra". Extrasolar Planets Encyclopaedia. Retrieved 3 October 2011.

This giant-star-related article is a stub. You can help Wikipedia by expanding it.

• v
• t
• e

This extrasolar-planet-related article is a stub. You can help Wikipedia by expanding it.

• v
• t
• e

На других языках

[de] 42 Draconis

[es] 42 Draconis

[ru] 42 Дракона