Superstar Search.

Planet hunter Geoffrey Marcy has paved his way into the superstar Hall of Fame. Since 1995, Marcy and a team of astronomers at the University of California at Berkeley have sleuthed out 25 extrasolar (outside our solar system) planets (see SW 9/6/99). But until recently they relied on complex evidence to back up their discoveries--with no visible proof.

That changed last November, as Marcy's team peered into the heavens through the most powerful optical telescopes in the world: the twin Keck telescopes, located on a remote Hawaiian volcano summit. The astronomers gazed at stars 153 light-years (895,000 billion miles) from earth. They detected six stars' wobbling motion, a first clue to the presence of planets orbiting around the stars.

For more visible evidence, the planet hunters turned to astronomer Gregory Henry at Arizona's Fairborn Observatory. Henry focused the small robotic "T8" telescope, which features a highly sensitive photometer (instrument measuring the brightness of starlight), on one promising star: HD 209458 in the constellation Pegasus. When a planet crosses in front of its star, it casts a shadow so that less light reaches Earth. As one planet was about to journey in front of HD 209458, light radiating from the star dimmed by 1.7 percent at the exact moment the planet was predicted to pass in front of it. "Until then we didn't have direct confirmation that these were really planets" says Henry. "This provides the final proof"

Astronomers are now scouring the universe with a new array of telescopes that use the electromagnetic spectrum--from radio waves to X-rays--to visualize cosmic phenomena across the vast reaches of space. For a first-hand view, read on!

COOL SIGHT

Color-enhanced image of the Eskimo nebula, or cloud of interstellar gas, as seen by the Keck telescope. The nebula is 2,930 light-years away.

COOL SIGHT

A false-color VLA radio image shows jets of plasma, a mixture of electrons and atomic nuclei, in Galaxy IC 708.

Very Large Array Radio Telescope

Have you ever thought you can "hear" the hum of the sky? In 1932 a Bell Telephone engineer tracking sources of radio static detected a continuous hiss in the sky. It turned out the noise came from the heart of our own Milky Way galaxy (large group of stars). Since then, astronomers have learned much about deep space simply by listening to it.

The Very Large Array (VLA) radio telescope near Sorroro, N. M., is an awesome formation of 27 radio dishes, each 25 meters (82 feet) wide and weighing 230 tons. Sitting on railroad tracks, the telescopes move in formation to view different regions of the universe. Since radio waves are so much longer than light waves (see page 19), radio telescopes need to be huge. So computers coordinate signals from each VLA antenna to operate as one 22-mile wide mega-telescope.

Gazing through a traditional optical telescope, you'd see a galaxy 50 billion light years away from Earth as a fuzzy oval of light. A new VLA image, on the other hand, is sharp enough to reveal twin jets of gas shooting from the galaxy center. The jets may originate in a black hole (invisible region possibly caused by a collapsed star) weighing as much as 3 billion of our suns.

Last December, international scientists used the VLA to witness the birth process of solar systems for the first time. They saw the process of supernovae (massive exploding stars) expanding into fireballs, spewing out elements necessary to form new stars and planets. Only a radio telescope could have gathered this amazing data, because the supernovae were hidden from traditional optical telescopes by thick dust.

LIGO Dectectors

Think you know someone with long arms? Imagine an L-shaped telescope with arms 2.5 miles long, and you'll get an idea of LIGO (Laser Interferometer Gravitational- Wave Observatory)! Teams of scientists at the California and Massachusetts Institutes of Technology are building two separate LIGO observatories in Louisiana and Washington. LIGO's aim? To detect gravitational waves, ripples in space and time produced by violent events in the distant universe, such as the collision of two black holes or exploding supernovae.

Physicist Albert Einstein predicted the existence of gravity waves in 1916, but until now no technology has been powerful enough to prove his theory. Scientists hope next year, when LIGO should be up and "viewing" the telescopes will do the trick. "The waves are there," says Mark Coles, head of LIGO in Louisiana. "It's just a question of having the technology to detect them."

The two separate LIGO installations, 2,000 miles apart and costing $160 million each, are necessary to make sure the telescopes actually detect gravity waves from space--not Earth. (LIGO can mistake local disturbances like tiny earthquakes for gravity waves coming from space.) Each of LIGO's arms or "detectors" is a 1.2-meter (4-foot) long, concrete-covered vacuum pipe. The detectors are fitted with a laser interferometer, or elaborate light-beam and mirror system. The lasers register only gravity waves--not light.

Physicists also hope LIGO will give them a new perspective from which to study the universe. A planned upgrade of LIGO in 2004 should make the telescopes sensitive enough to detect a collision of neutron stars (the cores of burned out supernovae) and merging black holes.

COOL FACT

LIGO will soon join a global network of gravity-wave observatories. One should be completed in Italy by 2002; others are planned in Germany and Japan.

Chandra X-Ray Observatory 

What can read a comic strip from a kilometer away or the letters on a STOP sign 9 km (12 mi) off?. Try NASA's new Chandra (KAHN-drah) X-ray telescope. In July 1999, space shuttle Columbia launched the 14-meter (45-foot) long telescope into Earth's orbit. Chandra traps X-rays (highenergy electromagnetic waves) produced by some of the most gigantic explosions in the universe. Astronomers are hoping for new data and detailed images of exploding and collapsing stars, distant quasars (distant young galaxies) and pulsars (pulsating collapsed stars).

Since Earth's atmosphere absorbs X-rays and prevents them from reaching the ground, X-ray telescopes must fly high above the planet in order to perform their job. In its elliptical orbit, Chandra will travel as far as 140,000 km (87,000 mi) above Earth, or one-third the distance to the moon! That means at its apogee (furthest point from Earth), Chandra will soar 200 times higher than the visible light-gathering Hubble Space Telescope.

X-rays from distant space radiate so much energy, they penetrate rather than bounce off mirrors. But since telescopes function by reflecting light, Chandra has specially designed mirrors that are positioned almost parallel to incoming X-rays. In this way, X-rays barely graze the mirrors and ricochet off instead. Four sets of incredibly smooth, barrel-shaped mirrors focus X-rays onto detectors that record their direction and energy. Chandra also features instruments that separate X-rays into spectra, divisions of radiation according to wavelength. Two cameras then receive the information to produce images of the X-rays' sources.

COOL SlGHT

A Chandra X-ray image (1) of Eta Carinae, our galaxy's most luminous star (7,500 light years from Earth), as compared to an optical image by the Hubble Space Telescope (2). At right, an artist's rendition, of Chandra.