# Astronomy help?

These are the questions I am having trouble with, please help! Thank you!!

1. The Andromeda Galaxy (called M31) is one of the nearby galaxies to the Milky Way. The distance to it is known to be 2.5 million lyr, while its linear size is 67 kpc. How large is M31 in angular distance scale? Provide your answer in both radian and arcminute.

2. For simplicity, let’s assume that the surface temperature of the Sun is 6000 K and its blackbody radiation peaks at 500 nm. If you observe a star whose surface temperature is 2000 K, what would be the wavelength of its peak blackbody radiation? If you found a star that you have been observing has the peak blackbody radiation at 125 nm, what would be the surface temperature of the star?

3. In the class we show that the solar luminosity by blackbody radiation is approximately 3.9x10^26J/sec. Assuming again the surface temperature of the Sun is 6000 K, what would be the size (in radius) of the Sun? Is this larger than the distance between Earth and the Moon, which is about 3.8x10^8m?