News Release

Comet Experts at Johns Hopkins to Study Hale-Bopp

About Hale-Bopp: By late March and early April Comet Hale-Bopp may be one of the brightest comets of the century, as it makes it closest approach to the sun and Earth. It will not return for about 3,000 years. Astronomers at The Johns Hopkins University have used the Hubble Space Telescope for a year-long study of Hale-Bopp, learning new details about the comet. As Hale-Bopp makes its closest approach, the astronomers and graduate students will observe Hale-Bopp with an infrared telescope in Hawaii and with a sounding rocket equipped with an ultraviolet spectrograph.

JHU Experts: Astrophysicist Harold Weaver specializes in comet research, using both space-borne and ground-based telescopes. He was among astronomers who in 1986 proved that the core of Halley's Comet contains water ice, and he led a research team studying Comet Shoemaker-Levy 9, which collided with Jupiter in 1994. Weaver led a team of astronomers in conducting the year- long study of Hale-Bopp with the Hubble Telescope.

Paul Feldman, chairman of the Hopkins Department of Physics and Astronomy, also has conducted extensive research on comets over the years, using the Hubble telescope, sounding rockets and other instruments. He led a team of astronomers studying comets using a satellite called the International Ultraviolet Explorer, which operated between 1978 and 1996. Feldman is working with other scientists and graduate students to observe Hale-Bopp with a sounding rocket, which will rise above the Earth's atmosphere to observe ultraviolet light from the comet.

For additional information, or to get in touch with Weaver or Feldman, journalists may contact Emil Venere at the above phone number and e-mail address.

Related Web Sites:
http://www.skypub.com/comets/comets.shtml
http://www.pha.jhu.edu/~weaver/
http://www.pha.jhu.edu/people/faculty/pdf.html

Fact Sheet: Comet Hale-Bopp

In the Northern Hemisphere, the best time to view the comet will be shortly before dawn and shortly after sunset from late March to mid-April. From March 26 through April 8, the sky will be free of moonlight after dusk, making it easier to see the comet at the time when it will be at its brightest. It will set about an hour after sunset, making it visible for a short time each night.

The comet should be viewed from areas far away from city lights. People should look to the west-northwest, near the horizon, about 45 minutes after sunset for their best view of Hale-Bopp.

As April progresses, Hale-Bopp will be visible for an increasingly longer time after sunset, but it probably will be fading in brightness. That's why the first couple of weeks in April will offer the best viewing.

Hale-Bopp is the second comet to visit the inner solar system within a year. But the other one, comet Hyakutake, was only visible late at night. "In a sense, Hale-Bopp is better for the public because people don't want to stay out in the middle of the night; they can observe it right around dinner time," said Weaver, a research scientist in the Johns Hopkins Department of Physics and Astronomy.

Astronomers cannot use the Hubble Space Telescope to view the comet during its closest approach to the sun. They did observe Hale-Bopp with the Hubble Telescope for a one-year period that ended in mid-October 1996, when the comet came too close to the sun from Earth's perspective to be viewed safely with the space telescope. Looking too close to the sun could subject the telescope to dangerous heating. For that reason, astronomers will have to use telescopes on the ground and on sounding rockets to observe the comet as it approaches its rendezvous with the sun.

Hale-Bopp was named after its discoverers, Alan Hale of Cloudcroft, N.M., who has a Ph.D. in astronomy, and amateur astronomer Thomas Bopp, of Glendale, Ariz. They discovered the comet independently in July 1995.

General Facts about Comets

Whereas the planets have undergone major changes over time from geological, thermal and atmospheric processes, the comets have likely remained much as they were when they first formed. They have been preserved in the icy cold of the solar system's outermost regions.

"We think that when you look at a comet today, you are looking back into the past," Weaver said.

Comets come from two regions in the outer solar system. One region is a disk of icy bodies called the Kuiper Belt, located outside the orbit of Neptune. The other region, called the Oort Cloud, is much larger and may extend to 9 trillion miles from the sun, nearly half way to the nearest star, Alpha Centauri. Comets in the Oort Cloud sometimes end up in orbits that take them into the inner solar system when they are jostled out of place by the gravitational field of a star, or a giant molecular cloud, from which new stars form. Scientists believe that is what happened to Hale-Bopp at least 30,000 years ago. The comet currently takes roughly 3,000 years to orbit the sun, so it will take that long to return.

Another class of comets, called "short-period" comets, take less than 200 years to complete an orbit around the sun and are thought to have originated in the Kuiper Belt.