Midterm Solutions

2 au from the sun in wm2 flux luminosityarea l4d2

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: is 4.74, and using the standard definition of magnitude: Mbol(Vega) – Mbol(Sun) =  ­2.5log10(LVega/LSun) => LVega = LSun x 10 ­0.4(0.72 ­4.74) = 41 LSun L = 4πR2σT4 => R = (L/4πσT4)1/2 Or in solar units: (R/R¤) = (L/L¤)1/2(T/T¤) ­2 = (41)1/2(9600/5800) ­2 R = 2.3 R¤ This is a dwarf star. (f) [10 pts] What is the apparent angular size (diameter) of Vega in arcseconds as viewed from Earth? Can this be resolved with the Keck telescopes (resolution ≈ 0.05 arcseconds) θ (“) = diameter (AU) / distance (pc) = 2 x radius (AU) / distance (pc) = 2 x (2.3 R¤) x (6.96x108 m/R¤) x (AU/1.50x1011 m) / 7.7 pc = 2.8x10 ­3 arcseconds or 2.8 milliarcseconds This could not be resolved with Keck. Page 6 of 16 Physics 160 Fall 2013 Midterm Exam (2) [Total: 50 pt] Taking Jupiter’s Temperature. (a) [5 pts] What is the radiant flux received at Jupiter (orbital rad...
View Full Document

Ask a homework question - tutors are online