Lesson plan
Orion OB1
Orion OB1 (Ori OB1) is a contingent group of several dozen hot giant stars of spectral types O and B in Orion. Associated are thousands of lower-mass stars, and a (smaller but significant) number of protostars. It is part of the larger Orion molecular cloud complex. Owing to its relative closeness and complexity it is the most closely studied OB association. The Orion OB1 consists of the following subgroups: *Orion OB1a – the group of stars northwest of the Orion Belt stars with an average age of about 12 million years. Within this grouping is another subgroup known as the 25 Orionis group. They are located near the star of 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 approximately 8 million years and is further subdivided into three subgroups. *Orion OB1c – the stars in Orion's Sword that are created by 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) Signatures of stellar debris disk evolution have been detected in the 1a and 1b subgroups.
Article summary
Orion OB1 (Ori OB1) is a contingent group of several dozen hot giant stars of spectral types O and B in Orion. Associated are thousands of lower-mass stars, and a (smaller but significant) number of protostars. It is part of the larger Orion molecular cloud complex. Owing to its relative closeness and complexity it is the most closely studied OB association. The Orion OB1 consists of the following subgroups: *Orion OB1a – the group of stars northwest of the Orion Belt stars with an average age of about 12 million years. Within this grouping is another subgroup known as the 25 Orionis group. They are located near the star of 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 approximately 8 million years and is further subdivided into three subgroups. *Orion OB1c – the stars in Orion's Sword that are created by 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) Signatures of stellar debris disk evolution have been detected in the 1a and 1b subgroups.
Key claims
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.