Midterm Solutions

2 nm a 5 pts what is the distance to vega in pc

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Unformatted text preview: Long ­Answer Questions Answer as many of the following questions as you can. Full credit for this part is 90 points; any additional points you earn above this will be added as 30% bonus points (for a maximum of 120 points). (1) [Total: 40 pt] Let’s meet Vega Vega (α Lyr) is the brightest star in the constellation Lyra, an A0 V star which by definition has an apparent visual magnitude V = 0. It also has a parallax π = 0.130 arcseconds, a proper motion of µ = 0.35 arcseconds/year and a surface temperature of 9600 K. Its Balmer Hα line (n = 2 ­>3) is observed to be at 656.2 nm. (a) [5 pts] What is the distance to Vega in pc? Distance (pc) = 1/π (arcseconds) = 1/0.130 = 7.7 pc (b) [5 pts] What is the absolute visual magnitude of Vega? M – m =  ­5log10(d/10 pc) => MV = V  ­ 5log10(d/10 pc) = 0 – 5log10(7.7 pc/10 pc) = 0.57 mag Page 4 of 16 Physics 160 Fall 2013 Midterm Exam (c) [5 pts]...
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