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NASA's Space Place

Build It, and the Universe Will Come
by Dr. Marc Rayman

The largest stars are so big that they may be as much as 2,000,000,000 (2 billion) miles across. If a star that big were in the center of our solar system, where the Sun is now, it would be so big that it would swallow up all the planets from Mercury to Saturn, including Earth! The Sun is about 860,000 (860 thousand) miles across. If you rode in a car at 60 miles/hour, it would take 5 whole years to drive all the way around the Sun—without any rest or gas stops!

All stars are so huge that our entire Earth, with all its oceans, mountains, cities, forests, deserts, and everything else is tiny compared to them. If the largest star were a ball as tall as your school room, Earth would be about the thickness of one of your hairs.

By the way, you might be able to go outside on the next clear night and see one of the largest stars. Try to find the lovely constellation Orion, with its distinctive "belt" of 3 stars in the center, and then look above the belt to the nearest bright star. It may appear just slightly red. It has the odd name Betelgeuse (pronounced BAY-tell-juice). It may not be the largest star, but it is certainly one of the largest. We don't know its exact size, but it is around 600,000,000 (600 million) miles across. It could stretch from where the Sun is out past the orbit of Mars, and might even get all the way to Jupiter.

As long as you are looking at Orion, notice the bright star below the belt, about the same distance from the belt as Betelgeuse but in the opposite direction. It is called Rigel (pronounced like RYE-jell), and it is one of the brightest stars around. It is farther away than most of the stars we see without a telescope, but it still manages to outshine most of them. It is about 40,000 (40 thousand) times brighter than the Sun.

To help you find Orion, you can download a star finder at The Space Place, http://spaceplace.nasa.gov/starfinder. Orion is visible November through April.

Many other stars are much bigger than our Sun, but lots of them are smaller too.

This article was provided through the courtesy of the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, under a contract with the National Aeronautics and Space Administration and support from the U.S. Department of Commerce National Oceanic and Atmospheric Administration.


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