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This is a picture of a Brownlee particle, which may be what a comet is made of.
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JPL

Brownlee Particles

This example of Interstellar Dust is a perfect example of the kind of rocky material comets may be made of. The grains themselves seem to be made of smaller grains. There are many holes, or pores. In a proper comet, these holes would be filled with ice.

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Cool It! Game

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Meteor Showers

A meteor shower is an astronomical event during which many meteors can be seen in a short period of time. Most meteor showers have a peak activity period that lasts between several hours and a couple of...more

Meteors

Meteors are streaks of light, usually lasting just a few seconds, which people occasionally see in the night sky. They are sometimes called "shooting stars" or "falling stars", though they are not stars...more

Comet Hale-Bopp

Comet Hale-Bopp was one of the brightest comets of all time. Astronomers witnessed the comet spew out intermittent bursts of dust. The surface seemed to be an incredibly dynamic place, with 'vents' being...more

Missions to Halley's comet in 1986

Six spacecraft flew to Halley's comet in 1986. There were two spacecraft launched from Japan, named Suisei and Sakigake, and two from the Soviet Union, named Vega 1 & 2. One spacecraft, ICE, was from the...more

The Jupiter family of comets

Astronomers have noticed a group of comets which they call the Jupiter Family of Comets. This family of comets is to be found circling between Jupiter and the sun, as shown in this picture. The comets...more

What we learned from Comet Shoemaker-Levy 9

Scientists have learned a great deal from the crash of comet Shoemaker-Levy 9. Scientists traced the orbit of the comet backwards in time to guess its origin. The crash of a comet like Shoemaker-Levy 9...more

The trajectory of Comet Shoemaker-Levy 9 over time

Mathematical theory suggests that comet Shoemaker-Levy 9 was likely a short-period comet which was captured into orbit around Jupiter in 1929. This orbit ended with a collision of the comet with Jupiter...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA