Orion OB1 Association
The Orion OB1 stellar association is the group of hot giant stars in a large cluster. They are spectral types O and B. There are thousands of lower-mass stars also in this group, and some protostars.
The association is part of the larger Orion Molecular Cloud Complex. It is the most closely studied OB association.[1]
The Orion OB1 association has these subgroups:[1][2]
- Orion OB1a - the group of stars northwest of the Orion Belt stars with an average age of about 12 million years. Within this group is a subgroup known as the 25 Orionis group.[3][4] They are near the star Bellatrix.
- Orion OB1b - the three bright stars ζ Ori (Alnitak), ε Ori (Alnilam), and δ Ori (Mintaka) which make up the asterism known as "Orion's Belt", and minor stars. This group has an average age of about eight million years and has three subgroups.[5][6]
- Orion OB1c - the stars in Orion's Sword: 42 Orionis, θ Orionis, and ι Orionis. These stars are about 3-6 million years old.
- Orion OB1d - the stars of the Orion Nebula and M43 (the youngest stars)
Signs of stellar debris disk have been found in the 1a and 1b subgroups. That is a circumstellar disk of dust and debris in orbit around a star.[7][8]
References
- ↑ 1.0 1.1 Brown A.G.A.. The Orion OB1 association. 1: Stellar content. Astronomy and Astrophysics 289 (1) (1994). p. 101–120.
- ↑ Blaauw, Adriaan. The O Associations in the Solar neighborhood. Annual Review of Astronomy and Astrophysics 2 (1) (1964). p. 213–246. doi:10.1146/annurev.aa.02.090164.001241.
- ↑ Briceño, César. 25 Orionis: A kinematically distinct 10 mya-old group in Orion OB1a. The Astronomical Journal 661 (2) (2007). p. 1119–1128. doi:10.1086/513087.
- ↑ Harper, Graham M.. A New VLA-Hipparcos distance to Betelgeuse and its implications. The Astronomical Journal 135 (4) (2008). p. 1430–40. doi:10.1088/0004-6256/135/4/1430.
- ↑ Warren W.H., Jr.. A photometric study of the Orion OB 1 association. I - Observational data. Astrophysical Journal Supplement Series 34 (1977). p. 115–206. doi:10.1086/190446.
- ↑ Warren W.H., Jr.. A photometric study of the Orion OB 1 association. III - Subgroup analyses. Astrophysical Journal Supplement Series 36 (1978). p. 497–572. doi:10.1086/190510.
- ↑ N. Calvet et al; The Astronomical Journal 129:935–946 (2005)
- ↑ J. Hernandez et al., Astrophys. J. 652:472-481 (2006)