This diagram shows the shape and size of the orbit of Comet Wild 2. The comet's orbit is shown in aqua. The orbits of Jupiter, Mars, and Earth are also shown. Click on image for full size (6K GIF) Image courtesy NASA/JPL.

Comet Wild 2 is a short-period comet that orbits the Sun once every 6.39 years. A Swiss astronomer named Paul Wild discovered it on January 6, 1978. Wild 2 is pronounced "Vilt 2". The comet comes about as close to the Sun as the planet Mars, and loops about as far away as the planet Jupiter. The comet's nucleus is about 5 km (3 miles) across, so Wild 2 is not an especially large comet.

Astronomers routinely calculate the positions of newly discovered comets at earlier times to make sure someone hasn't re-discovered a previously known comet. The scientists made a surprising discovery when they calculated the orbit of Wild 2 backwards in time to the years before its discovery. They realized that on September 10, 1974, the comet passed very close to Jupiter and had its orbit substantially altered by that giant planet's gravity. Before 1974, Wild's orbit was in the outer solar system, ranging between Jupiter's and Uranus' distance from the Sun. So, until recently, Wild 2 had never come very close to the Sun.

Since Wild 2 has only taken a few swings near the heat of the Sun, most of its ices have not been melted away. Apparently Wild 2 has been kept in cold storage since the early days of our Solar System, which makes it a very interesting comet to study. Studies of Wild 2 may help scientists understand what the materials that originally formed our Solar System were like.

Because Wild 2 (which is also known as Comet 81P/Wild 2) is in such a pristine condition, scientists chose it as the target of a space mission called Stardust. The Stardust spacecraft flew by Wild 2 in January 2004 and captured some tiny particles from the comet. It will return those particles to Earth in 2006, giving scientists their first sample of cometary materials that may shed light on the history and evolution of our Solar System. Stardust also shot the best images ever taken of the nucleus of a comet during its flyby.

This picture shows the shape and size of the orbit of Comet Wild 2. The comet's orbit is aqua. You can also see the orbits of Jupiter, Mars, and Earth. Click on image for full size (6K GIF) Image courtesy NASA/JPL.

Comet Wild 2 is named after the scientist who discovered it. Paul Wild is an astronomer from Switzerland who discovered the comet in January 1978. Wild 2 is pronounced "Vilt 2".

The comet orbits the Sun once every 6.39 years, which is a pretty short time for a comet. Some comets take more than 100 years to go around the Sun one time! The comet's orbit is not a circle. Its orbit is shaped more like an oval, which astronomers call an ellipse. When the comet is at one end of the ellipse it is as close to the Sun as it gets. When it is at the other end, it is far from the Sun. The orbit of Wild 2 brings it a bit closer to the Sun than the planet Mars. The orbit also swings the comet out beyond the orbit of Jupiter.

When we see a comet from Earth, we actually see the dust and gas the comet gives off. The dust and gas form a fuzzy head called the "coma" and tails that are thousands of kilometers (miles) long. The solid part of a comet is called the nucleus, and is in the middle of the coma. The nucleus of Wild 2 is only about five km (three miles) across.

A spacecraft named Stardust flew by Comet Wild 2 in January 2004. I took some very nice pictures of the nucleus and gathered some dust samples. It will bring the dust back to Earth so scientists can study it.

This picture shows the shape and size of the orbit of Comet Wild 2. The comet's orbit is aqua. You can also see the orbits of Jupiter, Mars, and Earth. Click on image for full size (6K GIF) Image courtesy NASA/JPL.

Comet Wild 2 is named after the scientist who discovered it. Paul Wild is an astronomer from Switzerland who discovered the comet in January 1978. Wild 2 is pronounced "Vilt 2".

It takes the comet a little more than six years to go around the Sun once. That is a pretty short time for a comet. Some comets take more than 100 years to go around the Sun one time! The orbit of the comet is not a circle. Its orbit is shaped more like an oval, which astronomers call an ellipse. When the comet is at one end of the ellipse it is as close to the Sun as it gets. When it is at the other end, it is far from the Sun. The orbit of Wild 2 brings it a bit closer to the Sun than the planet Mars. The orbit also swings the comet out beyond the orbit of Jupiter.

When we see a comet from Earth, what we really see is the dust and gas the comet gives off. The dust and gas form a fuzzy head called the "coma". They also form the comet's tails that are thousands of kilometers (miles) long. The solid part of a comet is called the nucleus. The nucleus is in the middle of the coma. The nucleus of Wild 2 is only about five km (three miles) across. The nucleus is much smaller than the coma or the tails.

A spacecraft named Stardust flew by Comet Wild 2 in January 2004. I took some very nice pictures of the nucleus. It also gathered some dust samples. It will bring the dust back to Earth so scientists can study it.