Size Does Matter

In the article, “Astronomers observe a dying red giant star’s final act“, from the University of California – Los Angeles, talks about a team of astronomers discovering a star called LL Pegasi, a red giant losing a lot of mass, releasing gas in a spiral pattern. Due to it having a companion star, the orbital motion causes the release of gas to form a spiral pattern.

After reading this article, I find it so hard to comprehend the size of stars such as red giants. I always thought they released less energy since they are cooler then their previous state, but I was totally wrong.  At first, I thought that an object that is small and has a higher temperature releases more energy, but I didn’t realize how much size impacted the luminosity.

The article corresponds to our conceptual objective, ” I can explain how astronomers determine the luminosity, the temperature and size of stars”, because we can see this star due to the fact that LL Pegasi is a red giant. This means it’s luminosity has to be large and the release in gases can help them determine the size. The way astronomers determine the size of the star is finding out the temperature it is and how much energy is it releases. In our lecture tutorial pages 55-58, about luminosity, temperature, and size, the second part of this section follows the the rule that the luminosity can increase by either increasing the size, or temperature.

Image result for part 2: application to the h-r diagram

The diagram above shows the temperature at the horizontal axis and luminosity on the vertical axis. As you can see, if you follow the rule previously stated, the 2 stars at the very top one being (hot, bright) and the other being (cool, bright) are roughly emitting the same amount of energy. But, the star that is cooler has to be larger. The reason for this is due to the fact that the cooler star is releasing the same amount of energy. The hotter the star is, it would look blue and the cooler star is, it would look red. This is due to the wavelengths of the energy emitted. The longer cooler wavelengths are associated with red and the shorter hotter wavelengths are associated with blue.


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