Epoch J2000.0 Equinox J2000.0
|Right ascension||18h 25m 59.14s|
|Declination||+65° 33′ 48.5″|
|Apparent magnitude (V)||4.833|
|B−V color index||1.187|
|Radial velocity (Rv)||32.17 ± 0.20 km/s|
|Proper motion (μ)||RA: 105.83 ± 0.21 mas/yr
Dec.: -27.24 ± 0.28 mas/yr
|Parallax (π)||10.36 ± 0.20 mas|
|Distance||315 ± 6 ly
(97 ± 2 pc)
|Absolute magnitude (MV)||–0.108|
|Mass||0.98 ± 0.05 M☉|
|Radius||22.03 ± 1 R☉|
|Surface gravity (log g)||0.929 cgs|
|Temperature||4200 ± 70 K|
|Age||9.49 × 109 years|
42 Draconis (abbreviated 42 Dra), also named Fafnir, 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.
Of spectral type K1.5III, the star has 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.
42 Draconis is the Flamsteed designation. Following its discovery the planet was designated 42 Draconis b. In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning names were Fafnir for this star and Orbitar for its planet.
The winning names were submitted by the Brevard Astronomical Society of Brevard County, Florida, United States. Fafnir was a Norse mythological dwarf who turned into a dragon ('Draco' is Latin for 'dragon'); Orbitar is a contrived word paying homage to the space launch and orbital operations of NASA.
42 Draconis b was discovered in 2009. It is an example of a super-Jupiter.
(in order from star)
|b (Orbitar)||≥3.88 ± 0.85 MJ||1.19 ± 0.01||479.1 ± 6.2||0.38 ± 0.06||—||—|
- van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. Vizier catalog entry
- NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
- NameExoWorlds The Process
- Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
- NameExoWorlds The Approved Names
- Döllinger, M. P.; et al. (2009). "Planetary companion candidates around the K giant stars 42 Draconis and HD 139 357". Astronomy and Astrophysics 499 (3): 935–942. arXiv:0903.3593. Bibcode:2009A&A...499..935D. doi:10.1051/0004-6361/200810837.
- Jean Schneider (2011). "Notes for star 42 Dra". Extrasolar Planets Encyclopaedia. Retrieved 3 October 2011.
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