70 Ophiuchi
| 70 Ophiuchi | |
|---|---|
| Observational Data | |
| Designation | 70 Oph P Oph HIP 88601 |
| Right ascension | 18h 05m 27.2851s[1][2] |
| Declination | +02° 30′ 00.3558″[1][2] |
| Constellation | Ophiuchus |
| Type of object | Main sequence star |
| Magnitude | Apparent Mag: +4.03[3] Absolute Mag: +5.50[3] |
| Astrometry | |
| Distance from Earth | 16.58 ly[3] |
| Radial velocity | -5.800 ± 0.0002 km/s[1][4] |
| Proper motion | RA: 124.16 mas/yr[1][2] Dec: -962.82 mas/yr[1][2] |
| Parallax | 196.72 ± 0.83 mas[1][2] |
70 Ophiuchi (70 Oph, P Oph, HIP 88601) is a binary star in the constellation of Ophiuchus.[5] William Herschel is known to have observed the pair in August 1779 but credited Christian Mayer as having discovered this earlier.[6] At a distance of roughly 16 light years, it is the 51st closest star to Earth. In fact it is so close, that the two stars can easily be resolved with a telescope or magnification larger than x75 and can be observed to complete one orbit every 90 years, one of the few star systems where this can be observed in a human lifetime.[7] The brighter primary star can be observed to have a yellow-golden color whereas the fainter secondary has a orange-red appearance.
Properties and structure
The 70 Ophiuchi system is located 16.58 light years from Earth.[3] The two stars are both K class yellow-orange dwarf stars and orbit each other with a period of 88.05 years and a mean separation of 23.3 Astronomical units (or 2 to 7 seconds of arc as seen from Earth).[8][9] The orbit is highly eccentric with an eccentricity of e=0.495, meaning the distance between the stars varies from 11.7 AU up to 34.8 AU.[6] The stars made their most recent close approach in 1989 and will next be at their maximum distance in 2028.[7] The plane of the orbit is inclined at an angle of 121.2° from Earth's perspective.[6]
It was thought from observations made between 1914 and 1943 that there may be another companion star or object present, but not seen, when an apparent 17 year cycle was discovered.[6] Such an object was thought to have a mass 10 times that of Jupiter and possibly be an exoplanet.[10] However, more recent studies suggest this was in error and that there are no masses larger than four Jupiter masses within 5.2 AU of either star.[6][11]
The larger primary star (designated 70 Ophiuchi A) has an apparent magnitude of +4.22.[5] It has a similar temperature to the Sun at 5290 Kelvin but is a little smaller with 85% the radius and 92% of the mass.[12] This leads it to emit only 0.51 times the radiation the Sun does. It is also known the rotate, with each rotation taking 19.7 days.[5] The other star, 70 Ophiuchi B, is smaller with a mass of 0.70 solar masses and radius 0.73 times that of Sol.[12][6] The secondary is thought to be a bit cooler than 70 Ophiuchi A at 4250 Kelvin and emit only 0.17 solar luminosites of radiation.[5]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 70 Ophiuchi. Simbad Astronomical Database. simbad.u-strasbg.fr. Retrieved on July 16, 2020.
- ↑ 2.0 2.1 2.2 2.3 2.4 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy & Astrophysics 474 (2): 653-664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V. arXiv:0708.1752
- ↑ 3.0 3.1 3.2 3.3 70 Ophiuchi. universeguide.com. Retrieved on July 16, 2020.
- ↑ Soubiran, C.; Jasniewicz, G.; Chemin, L. et al. (2018). "Gaia Data Release 2. The catalogue of radial velocity standard stars.". Astronomy and Astrophysics 616A (8). doi:10.1051/0004-6361/201832795. Bibcode: 2018A&A...616A...7S. arXiv:1804.09370
- ↑ 5.0 5.1 5.2 5.3 Jim Kaler (September 13, 2003). 70 Ophiuchi. Stars. stars.astro.illinois.edu. Retrieved on July 16, 2020.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 70 Ophiuchi 2?. solstation.com. Retrieved on July 16, 2020.
- ↑ 7.0 7.1 Nicole Aniston (September 06, 2018). A Speedy Little Double Star. cosmicpursuits.com. Retrieved on July 16, 2020.
- ↑ Bulk stellar properties Stellar temperatures. britannica.com. Retrieved on July 16, 2020.
- ↑ Batten, A. H.; Fletcher, J. M. (1991). "On The Orbital Period Of 70 Ophiuchi". The Astronomical Society of the Pacific 103 (664): 546. doi:10.1086/132851. Bibcode: 1991PASP..103..546B.
- ↑ Reuyl, Dirk; Holmberg, Erik (1943). "On the Existence of a Third Component in the System 70 Ophiuchi.". Astrophysical Journal 97: 41. doi:10.1086/144489. Bibcode: 1943ApJ....97...41R.
- ↑ Wittenmyer, Robert A.; Endl, Michael; Cochran, William D. et al. (2006). "Detection Limits from the McDonald Observatory Planet Search Program". The Astronomical Journal 132 (1): 177-188. doi:10.1086/504942. Bibcode: 2006AJ....132..177W. arXiv:astro-ph/0604171
- ↑ 12.0 12.1 The One Hundred Nearest Star Systems. recons.org. Retrieved on July 16, 2020.
