In the article, “Star brightness versus star luminosity” posted by earthsky.org relates to our eight objectives “I can explain how astronomers determine the luminosity, the temperature, and size of stars”. First the article talks about how stars are viewed with brightness either apparent magnitude which is how night a star looks from Earth, and absolute magnitude how bright it appears from light years away. According to the article two things that play a key role in the luminosity of a star is the mass, and the surface temperature. For the radius measure, the larger the radius the greater the luminosity. If two stars and they are the same size but the surface temperature is greater so would the luminosity. Luminosity is overall determined by how how much energy it’s putting out the hotter, closer, and larger it is the more luminous the smaller, further, and cooler it is the less luminous. In the article, it talks about how a HR diagram can help with categorizing stars by temperature, size, and lumiousity.in our textbooks on page 314 it talks about all the other things not related to this objective that the HR diagram shows.
Hot stars are in the left and colder stars are to the right, most luminous are at the top least luminous are at the bottom. One way to tell the temperature of a star is blue or blue-white stars are the hottest and oranges/ red are the cooler stars which we learned in our lecture tutorial.Astronomers also use spectral lines to determine temperature. Cooler stars have spectral lines of molecules they will break apart, it the temperature is not cool enough. Hotter stars have spectral lines of highly ionized elements need high temperature so the atoms will ionize. On the HR diagram, it shows that the larger stars are higher on the absolute magnitude, making them larger than most stars therefore telling its size. I found this article really helpful in helping to understand that it’s not all about size when it comes to a star’s luminosity. It also helped me understand how mass is not the only thing that determines a star’s temperature this article overall helped me get a better understanding of how to tell a star’s mass, temperature, and luminosity.