Compare the density of a white dwarf to a supernova.
8. It would seem that a bright star is closer to earth than a dim star. But this is not always the case. What other factor could explain a difference in brightness?
9. Explain how absolute magnitude compares the brightness of stars.
10. What are the two characteristics that the H-R diagram plots against each other?
Please answer the questions in order.
The density of a white dwarf is less than that of a supernova. While both these stages represent the end of the lifecycloe of a star, a white dwarf has less solar mass than a supernova. Sometimes a supernova can turn into a neutron star, where the mass is so dense, a teaspoon of it brought back to Earth would weigh several tons!
For #8, if a star is undergoing a supernova type of explosion, the surrounding area of space could be brilliantly illuminated for several days. It might be much further away than a closer, yet dimmer star, but looks closer because of the excessive light show.
For #9, there are two types of magnitude, which is star brightness: apparent and absolute. Apparent magnitude is what it looks like as you are looking at it with your eyes. Absolute is the correct measure of brightness, scaled with a spectroscope. The smaller the number, the brighter the star, so a star with a -4 is brighter than a +7.
And finally, #10, the two aspects the Hertzsprung-Russell diagram compares are star temperature and brightness, or magnitude. Different temperature stars will give different colors, blue being the hottest and red being the coolest. Our sun is in-between, a medium yellow star.