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A trio of new planets.


With the discovery last month of three more planets orbiting nearby stars, the number of proposed extrasolar planets now totals more than 50. The three objects were found with a high-precision spectrograph that analyzes starlight beaming into the 4-meter Anglo-Australian Telescope The Anglo-Australian Telescope (AAT) is a 3.9 m equatorially mounted telescope operated by the Anglo-Australian Observatory and situated at the Siding Spring Observatory, Australia at an altitude of a little over 1100 m.  near Coonabarabran, Australia. Researchers have used the telescope since 1998 to search for planets among 200 nearby stars in the southern sky.

The lightest of the three planets is at least 84 percent as massive as Jupiter and lies within roasting distance of, its parent star, orbiting at about one-tenth the distance that Mercury circles the sun. That new find whips around its star in a mere 3 days.

The heaviest of the bodies, an object with a minimum mass nearly twice that of Jupiter, has an elliptical el·lip·tic   or el·lip·ti·cal
adj.
1. Of, relating to, or having the shape of an ellipse.

2. Containing or characterized by ellipsis.

3.
a.
 orbit and takes just over 2 Earth years to orbit its parent star, mu Ara, in the constellation Altar. The planet's average distance from its parent is just slightly greater than Mars' average distance from the sun

The middle-weight object, which seems the, most intriguing, is at least 1.26 times as massive as Jupiter. It has a circular orbit
For other meanings of the term "orbit", see orbit (disambiguation)


In astrodynamics or celestial mechanics a circular orbit is an elliptic orbit with the eccentricity equal to 0.
 and lies at an Earthlike distance from its parent star, epsilon Reticulum reticulum /re·tic·u·lum/ (re-tik´u-lum) pl. retic´ula   [L.]
1. a small network, especially a protoplasmic network in cells.

2. reticular tissue.
. It orbits its star every 426 days. Located in the constellation Net, this planet has the largest circular orbit of any planet yet detected outside the solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. , notes theorist Alan P. Boss of the Carnegie Institution of Washington The introduction to this article may be too long. Please help improve the introduction by moving some material from it into the body of the article according to the suggestions at  (D.C.)

"This is reassuring that we will [eventually] find Jupiter-mass planets in circular, Jupiterlike orbits," he says. Because such planets reside much farther from their parent star than Earth does from the sun, they would act as a shield protecting inner Earthlike planets from comets and other space debris, Boss says.

The discovery team, which includes Chris Tinney of the Anglo-Australian Observatory, relies on a standard technique to hunt planets. As a planet orbits, it causes its star to move back and forth. Researchers detect that wobble wobble /wob·ble/ (wob´'l) to move unsteadily or unsurely back and forth or from side to side. See under hypothesis.

wob·ble
n.
1.
 by recording a periodic shift in frequency of the light emitted by the star.
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Article Details
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Author:Cowen, Ron
Publication:Science News
Article Type:Brief Article
Date:Jan 13, 2001
Words:342
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