What Is The Biggest Star In The Universe?

In the article, What is the Biggest Star in the Universe?, on universetoday.com author Fraser Cain discusses how astronomers determine the different sizes and class of stars. When determining a star’s size, one must consider its solar mass and solar radius. Since our own sun is the closest star to Earth, astronomers use that for a sense of a scale. They have used the terms “solar radius” and “solar mass” to compare stars that are greater or smaller than the sun. Stars are classified based on their characteristics, such as absolute magnitude, spectral type, surface temperature, and luminosity. The Hertzsprung-Russell diagram is one of the methods used to classify the known stars of the universe.

The Hertzspirg-Russel diagram, showing the relation between star's color, AM. luminosity, and temperature. Credit: astronomy.starrynight.com

The Hertzsprung-Russell diagram ranges from a stars temperature that determines its color. The cooler stars are near the red end of the spectrum and those are mainly giants, supergiants and orange and red dwarfs. At the blue end of the spectrum, the stars are hotter including the white dwarfs. Our sun is approximately 5,800 K. It falls in the yellow part of the the diagram and is considered a yellow dwarf. In terms of mass, if stars were only considered by their mass, the absolute most massive star would be R136a1, a star located in the Large Magellanic Cloud. Astronomers believed that this star became so massive because many stars merged together to create just one huge star. The title for the largest known star in the universe now comes into consideration. The star at the top of the list is UY Scuti, located in the constellation Scutum. This is a bright red supergiant with a median radius of 1,708 solar radii. In other words, this star has a radius of about 15.9 AU. There are probably stars within the Milky Way that are even bigger than that, this is just the biggest one we know of.

This relates to class and the conceptual objective, “I can explain how astronomers use the Hertzsprung-Russell diagram to study properties of stars.” We have taken notes on the Hertzsprung-Russell diagram and what is included in it. There is the Main Sequence, which the majority of the stars are classified. Giants, not on the main sequence, are brighter than expected and very large. There are also red dwarfs that are cool and dim and there are white dwarfs that are hot and dim. We also worked on the H-R diagram exercise in our Lecture Tutorials workbook. We were able to see which stars are classified where and determine how the stars differ.

I enjoyed reading this article because it is interesting to know what the largest star in the universe is. Considering that our sun is fairly small compared to others, there are some stars that would engulf over half of our solar system with jut its size. Its fascinating.


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