Hamal

Hamal^[1] (also known as Alpha Arietis), is the brightest star in the zodiac constellation of Aries.^[2][3]

The star has an apparent magnitude of 2.0,^[4] it is the 50th brightest star in the night sky. Using the parallax measurements made with the Hipparcos astrometry satellite,^[5][6] Hamal is about 65.8 light years away from the Earth.^[7] It is a giant star that may have an planet with a mass greater than Jupiter orbiting around it.^[8]

Planetary system

In 2011, Byeong-Cheol Lee and others discovered a likely planet that might be in orbit around the star known as Hamal b (Alpha Arietis b). The planet was detected using the radial velocity method, using measurements that were made between 2003 and 2010 at the Bohyunsan Optical Astronomy Observatory in Korea. The planet has an orbital period of 381 days and an eccentricity of 0.25. The minimum value of this planet's mass is about 1.8 times the mass of Jupiter. The estimated semi-major axis of the orbit of the planet is 1.2 AU,^[9] which would give it a periapsis (closest) distance of 0.9 AU and an apoapsis (farthest) distance of 1.5 AU. By comparison, the star has a radius of 0.07 AU or about 10,471,850.9 km.

References

1. Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
2. HR 617, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line December 16, 2008.
3. Hamal Archived 2008-12-08 at the Wayback Machine, Stars, Jim Kaler. Accessed on line December 16, 2008.
4. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
5. Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; et al. (July 1997), "The Hipparcos Catalogue", Astronomy and Astrophysics, 323: L49–L52, Bibcode:1997A&A...323L..49P
6. Perryman, Michael (2010), "The Making of History's Greatest Star Map", Astronomers' Universe, Heidelberg: Springer-Verlag, Bibcode:2010mhgs.book.....P, doi:10.1007/978-3-642-11602-5, ISBN 978-3-642-11601-8
7. van Leeuwen, F. (November 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, S2CID 18759600
8. Lee, B.-C.; et al. (May 2011), "A likely exoplanet orbiting the oscillating K-giant α Arietis", Astronomy & Astrophysics, 529: A134, arXiv:1104.4431, Bibcode:2011A&A...529A.134L, doi:10.1051/0004-6361/201016293, S2CID 58906630
9. Lee, B.-C.; et al. (May 2011), "A likely exoplanet orbiting the oscillating K-giant α Arietis", Astronomy & Astrophysics, 529: A134, arXiv:1104.4431, Bibcode:2011A&A...529A.134L, doi:10.1051/0004-6361/201016293, S2CID 58906630