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Dig into Montana Before History: 11K Years of Hunter-Gatherers in the Rockies and Plains by D. H. MacDonald, Ph.D. See our online store book collection.

Exploratour - Evolution of the Solar System

This is an illustration of what the Oort cloud might be like.
Click on image for full size
JPL

Besides planets and moons, the solar system contains comets and asteroids. The place from which the comets come is thought to be a giant sphere surrounding the solar system. This sphere is called the Oort cloud. It is named after a scientist called Jan Oort who first thought of the idea in 1950. Thus comets are said to come from the Oort cloud.

The Oort cloud is very far away. In this picture, the solar system is buried deep within the cloud. An AU is the distance from the earth to the sun and is roughly equivalent to 100,000,000 miles. Mars is 1.5 AU from the sun, Jupiter is 5 AU from the sun, and Pluto is 39 AU from the sun. The Oort cloud is 100,000 AU away. So comets come from very far away indeed.

It is natural to ask "How did comets get so far away?" Astronomers are presently working to understand the answer to that question. This is one reason NASA studies comets.



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Our online store includes issues of NESTA's quarterly journal, The Earth Scientist, full of classroom activities on different topics in Earth and space science, ranging from seismology, rocks and minerals, oceanography, and Earth system science to astronomy!

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

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ExploraTour - Looking at the World in a Different Light

Imagine you found a pair of special glasses that not only gave you telescopic vision but gave you the ability to see all forms of radiant energy. The universe in visible light contains all the familiar...more

ExploraTour - Looking at the World in a Different Light

This is a volcano on the island of Miyake in Japan. It has erupted, sending hot lava and ash into the air, a total of ten times. The time after one eruption until the next occurred was about twenty years...more

ExploraTour - Looking at the World in a Different Light

This is a picture of a galaxy in visible light. A galaxy is a large number of stars, some like our sun, some bigger, some smaller and all moving together through space. This galaxy is called Centaurus...more

ExploraTour - Looking at the World in a Different Light

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF