Antares: Star & Facts

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  • 0:02 What Is Antares?
  • 1:09 Facts About Antares
  • 3:46 Lesson Summary
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Lesson Transcript
Instructor: Richard Cardenas

Richard Cardenas has taught Physics for 15 years. He has a Ph.D. in Physics with a focus on Biological Physics.

In this lesson, you will learn about a large, red object in the night sky visible from Earth. No, it's not the planet Mars; it is the star named Antares. Learn about where Antares is located and some of the properties that make Antares so special.

What Is Antares?

Most of the time, when people look at the night sky and see a red object flickering in the distance, they often assume it is the red planet Mars. However, there is another red object sharing the night sky, an object much further away and much larger than Mars. This object is a star called Antares. Antares is a red giant that belongs to the constellation Scorpio. A red giant is a large star that is relatively cool in temperature. To illustrate, the surface of the sun has a temperature of about 6,000 degrees Celsius, and a red giant has a temperature of about half of that.

Red giants are also stars that are in the last stages of existence. They are older stars that are about to transform into a different object in the sky like a white dwarf, a brown dwarf or a black hole. Antares is also one of the 20 brightest stars in the night sky. It is located about 500 light years away from us. This means that the light we see from Antares took 500 years to reach us! We are therefore seeing Antares as it looked 500 years ago.

Facts about Antares

First, it's important to be able to locate Antares in the night sky. It is the most prominent star of the constellation Scorpio and is also sometimes called 'alpha Scorpii.' Scorpio is one of the brightest constellations in the night sky. Its name is derived from the word 'scorpion', due to its shape, and Antares is located near the head of the scorpion. In the northern hemisphere, the constellation can be found close to the southern horizon. In the southern hemisphere, it is located high in the night sky.

Antares is part of a binary system. A binary system is a system composed of two stars that are so close that they orbit about a common central point. The earth's central point is the sun, and the earth revolves around the sun. Antares and its companion, Antares B, revolve around their common center of mass. Antares B is very dim compared to Antares A; therefore, it is not visible to the naked eye.

As we talked about before, Antares is a large star, about 700 times larger and 10,000 times brighter than our Sun (in solar system terms, that would be all the way to the orbit of Mars). But even though it is much larger than the sun, its density is much less than that of the sun. This is a fact that is often true of red giants. There are other red giants out there, like Betelguese, Aldebaran, Arcturus and Pollux.

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