University:
University of Toronto
Course:
AST201 | Exploring the Universe
Academic year:

2023
Views:

427

Pages:

4
Author:

Arlene R.

1. We find a binary system consisting of a 1 Solar mass star, still in its main sequence phase, and a white dwarf. Assume both stars formed at the same time and that they did not significantly influence each others’ evolution. Of the following, which could be possible ages for the system? Select all that apply and explain your answer in a few sentences. A. 107 yr B. 108 yr C. 109 yr D. 3x1010 yr E. 1011 yr Page 1 of 4 2. The red supergiant star Betelgeuse is the bright red star in the left shoulder of the constellation Orion. Its distance from Earth is approximately 640 light-years. If Betelgeuse were to explode as a supernova, its luminosity would be approximately 1010 LSun (hint only 1 sig fig here since the predictions for the luminosity of a supernova are uncertain) at its peak. Calculate the apparent brightness of supernova Betelgeuse in Watts/m2. Show all your work. Note that the Sun's luminosity 1 LSun = 3.8x1026 W. For comparison with your answer, the Sun's apparent brightness at Earth is about 1350 W/m2. The full moon has a much fainter apparent brightness of only ~0.001 W/m2. Page 2 of 4 3. You measure the velocity of a star at the outer edge of the Milky Way, located a distance of 50,000 lightyears from the galactic centre. You infer that the star's complete orbit around the centre of the galaxy will take 430 million years. Use Kepler's third law to determine the mass of the Milky Way within 50,000 lightyears. Round your answer to the nearest order of magnitude (1 significant figure). Page 3 of 4 4. The European GAIA space mission can measure parallaxes of moderately bright stars to a limit of about 1.6 x 10-5 arc-seconds. The previous best mission from the 1990s, Hipparcos, could measured parallaxes to a limit of 9.7x10-3 arc-seconds. How much farther away can GAIA map out stars, as compared with Hipparcos? Page 4 of 4

Determining the Possible Ages of a Binary Star System. Homework Assignment 2

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