Stars come in many shapes and sizes and they come in many colors. Some of the hottest stars in the Universe are blue giant stars. You see, the color of a star is defined by its temperature; the coolest stars are red, while the hottest ones appear blue. And the temperature of a star comes from its mass. The more massive a star, the hotter it’s going to be. Stars don’t get more more massive or hot than blue giant stars.
Blue giants blaze with a surface temperature of 20,000 Kelvin or more, and are extremely luminous. Just for comparison, a star like our Sun only has a surface temperature of about 6,000 Kelvin. A blue giant star can put out 10,000 times as much energy as the Sun. Astronomers categorize blue giants as type O or B stars, belonging to the luminosity class III. The can reach an absolute magnitude of -5 or -6.
The true monsters of the Universe are blue supergiant stars, like Rigel. These can be a blue star with surface temperatures of 20,000 – 50,000 Kelvin and can be 25 times larger than the Sun. Because they’re so large, and burn so hot, they use up their fuel very quickly. A middle-sized star like our Sun might last for 12 billion years, while a blue supergiant will detonate with a few hundred million years. The smaller stars will leave neutron stars or black holes behind, while the largest will just vaporize themselves completely.
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We have written many articles about stars on Universe Today. Here’s an article that looks for the biggest star in the Universe.