lec19 - Lecture 19 Classification of Stars Lecture 19...

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Lecture 19 Classification of Stars Purdue University, Astronomy 364 1 Lecture 19
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Reminder • HW05 has been posted. • Exam #1 has been graded and can be picked up in Rm 144. • Exam statistics: – Mean: 73.3 – Median: 75 – Standard deviation: 19.3 – Range: 39-97 – Distribution: 90-100: 7; 80-90: 11; 70-80: 9; 60-70: 7; 50-60: 3; 40-50: 3; 30-40: 1; 0-30: 1 Lecture 19 Purdue University, Astronomy 364 2
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Spectral Classification of Stars • O stars: T ~ 40000 K • B stars: T ~ 20000 K • A stars: T ~ 9000 K – Strong H Balmer line • F stars: T ~ 7000 K • G stars: T ~ 5500 K – The Sun is a G2 star. • K stars: T ~ 4500 K • M stars: T ~ 3000 K – The coolest M9 stars have a temperature of 2400 K. Lecture 18 Purdue University, Astronomy 364 3
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Brown Dwarfs • L dwarfs: T ~ 2000 K – Disappearance of TiO (and other oxide) absorption bands, which peaks at T ~ 3000 K . – Appearance of metal hydride absorption bands (FeH, CrH, etc). – The spectrum peaks in the infrared rather than in the visible band.
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lec19 - Lecture 19 Classification of Stars Lecture 19...

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