ASTR-1020 Astronomy II Homework 2 - Prof. Donald G. Luttermoser, Assignments of Astronomy

Download ASTR-1020 Astronomy II Homework 2 - Prof. Donald G. Luttermoser and more Assignments Astronomy in PDF only on Docsity! Astronomy II (ASTR-1020) — Homework 2 Due: 10 February 2009 The answers of this multiple choice homework are to be indicated on a Scantron sheet (either Form # 822 N-E or Ref # ABF-882) which you are to buy at the bookstore. Remember to use a No. 2 pencil on these Scantron sheets. Don’t forget to write your name and the Homework No. (e.g., 2) on the Scantron sheet. You are to turn in this Scantron at the beginning of class on the date indicated above. There are 20 questions on this homework assignment. Useful Constants G = 6.673 × 10−11 m3/s2/kg g = 9.80 m/s2 c = 3.00 × 105 km/s h = 6.626 × 10−34 J s k = 1.38 × 10−23 J/K H◦ = 50 km/sec/Mpc Mmoon = 7.35 × 1022 kg M = 1.99 × 1030 kg M⊕ = 5.98 × 1024 kg R⊕ = 6.38 × 106 m R = 6.96 × 108 m T = 5800 K 1 AU = 1.50 × 1011 m L = 3.90 × 1026 W e = 1.60 × 10−19 C σ = 5.67 × 10−8 W/m2/K4 me = 9.11 × 1031 kg mp = 1.67 × 10−27 kg 1 ly = 9.46 × 1015 m 1 pc = 3.09 × 1016 m 1 km = 103 m 1 hr = 3600 s 1 mi = 5280 ft 1 mi = 1.609 km 1 day = 24 hrs 1 yr = 365.24 days 1 Å = 10−10 m 1 nm = 10−9 m 1. Luminous stars can ionized the ISM which we see as a(n) a) reflection nebula b) dark nebula c) H I region d) H II region e) stellar nebula 2. As cloudlets shrink in size they spin faster. Which of the following results from this? a) a spherical shell b) a rectangular slab c) a flattened disk d) leptons e) baryons 3. Besides seeing nebula, the existence of the ISM can be seen by what in a stellar spectrum? a) wide absorption lines b) hydrogen lines c) helium lines d) narrow absorption lines e) resonance lines 4. A star has a (B − V ) color index of –0.4 and a (U − B) color index of 0.2. If this star has a visual magnitude of 2.6, what is its ultraviolet magnitude? a) –0.6 b) 0.2 c) 2.0 d) 2.4 e) 3.2 5. Why do H II regions take on a reddish appearance in photographs? a) From emission of hydrogen’s Lyman-alpha line. b) From emission of hydrogen’s Balmer-alpha line. c) From emission of the doubly-ionized oxygen line at 5007 Å. d) Because the temperature of the gas is such that most of its light is emitted in the red part of the spectrum. e) Because dust in the H II region scatters out blue light emitted from the nebula. 1