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Field Guide To New Planets - astronomers discover new planets
Discover, March, 2000 by Kathy A. Svitil
Also-ran Planets
Pulsar planets were the first worlds spotted outside our solar system, in 1991. Their suns are rapidly spinning neutron stars no more than six miles or so in diameter. They emit the energy of 10 suns in the form of deadly gamma rays, X rays, and other radiation. A pulsar's strong magnetic field focuses that energy into beams that sweep through the universe like a lighthouse signal. By measuring subtle variations in the arrival time of radio pulses from pulsars, astronomers are able to detect orbiting planets. At least three such uninhabitable planets lie in the constellation Virgo, 1,000 light-years from Earth; one is in the globular cluster M4, 5,500 light-years away. * Researchers have also detected what may be two planets using the gravitational microlensing technique: When an object like a planet or a star moves in front of a star, its gravity can act as a lens, bending and amplifying the star's light. Two planets detected this way orbit near the center of the Milky Way. * Finally, astronomers have caught telltale dips in the brightness of a pair of tightly orbiting red dwarfs in the constellation Draco. They suspect the dips are caused by a planet 2.5 times bigger than Earth that may be conducive to life.
Roasters In our own solar system, gas balls like Saturn, Jupiter, Uranus, and Neptune are frigid and far from the sun. However, outside our solar system, everything found so far seems to be reversed, with hot, gassy giants rotating precariously close to their parent stars. Because astronomers think none could have formed so near their suns, it's probable that they coalesced on the cooler edges of their planetary disks and then spiraled gradually inward. The very hottest ones, dubbed roasters by astrophysicist Adam Burrows of the University of Arizona, fly by just a few million miles from their suns, locked in corotation, with one side perpetually facing an inferno. * These are hellish worlds, with temperatures up to nearly 2,500 degrees Fahrenheit. Intense ultraviolet, X-ray, and charged-particle radiation heats their atmospheres. The view upward from the "surface" of these planets would be unlike anything on Earth. Clouds made of silicate would rain rock grains and iron droplets. Deeper within the planets, intense heat and pressure would turn hydrogen into a metal, and its convection would create a powerful magnetic field.
51 Pegasi LOCATION: constellation Pegasus, 50 light-years from Earth MASS: 140 Earths YEAR: 4.23 days MILES FROM SUN: 5 million TEMPERATURE: 1,560 [degrees] F. REPORTED: Oct. 6, 1995 * The first extra-solar planet to be discovered orbiting a sunlike star. Tau Bootis LOCATION: constellation Bootes, 50 light-years from Earth MASS: 1,230 Earths YEAR: 3.31 days MILES FROM SUN: 4.3 million TEMPERATURE: 2,190 [degrees] F. REPORTED: June 14,1996 * The most massive of the roasters, and possibly the hottest. Its star is three times as bright as our sun. HD187123 LOCATION: constellation Cygnus, 156 light-years from Earth MASS: 150 Earths YEAR: 3.097 days MILES FROM SUN: 3.9 million TEMPERATURE: 1,930 [degrees] F. REPORTED: Sept. 9,1998 * With the quickest orbit, this planet orbits very close to its star, which is similar to our sun. Planet finders think a second planet may orbit this star as well. HD75289 LOCATION: constellation Vela, 95 light-years from Earth. MASS: 130 Earths YEAR: 3.51 days MILES FROM SUN: 4.3 million TEMPERATURE: 2,040 [degrees] F. REPORTED: Feb. 1,1999 * The tightest extra-solar gas giant ever discovered. Its star is richer in metals than our own sun. HD217107 LOCATION: constellation Pisces, 64 light-years from Earth MASS: 404 Earths YEAR: 7.12 days MILES FROM SUN: 6.9 million TEMPERATURE: 1,250 [degrees] F. REPORTED: Oct. 10,1998 * A second planet, about four times the size of Jupiter, seems to be circling the same star.
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