SIGHTINGS


 
Two Huge Planets
Drifting Alone In Space Found
By John Fleck
Staff Writer
Albequerque Journal
6-1-99
 
 
CHICAGO -- Scientists using a New Mexico telescope have discovered two overgrown planets drifting alone in empty space -- the first such objects ever found.
 
More massive than Jupiter but too small to burn like our sun, the planetlike orbs represent a new type of extremely faint space object that scientists say may be as common as the stars in our galactic neighborhood.
 
Their discovery demonstrates the power of the New Mexico-based Sloan Digital Sky Survey, said Johns Hopkins University astronomer David Golimowski.
 
Golimowski and Princeton University astronomer Xiaohui Fan announced the discovery of the new objects, called "methane dwarfs," during this week's meeting of the American Astronomical Society.
 
Each is "too small to be a star but probably too large to be called a planet," Fan said. But while Jupiter and other similar objects have been found orbiting stars, Fan's methane dwarf was all by itself in empty space.
 
Soon after Fan's discovery in early spring, Golimowski found a second methane dwarf in data collected by the Sloan telescope.
 
Follow-up observations with telescopes in New Mexico and Hawaii showed methane in their atmospheres, as in the atmosphere of Jupiter. The scientists have only a rough idea of the objects' size but estimate they're 10 to 70 times the mass of Jupiter, the largest planet in our solar system. That's at most 7 percent the size of our sun.
 
Located at Apache Point Observatory in the mountains above Alamogordo, the Sloan is in the first year of a five-year project to map the sky above the northern hemisphere in unprecedented detail.
 
It's a joint project of a consortium of nine universities and research labs in the United States, Japan and Germany. Fan discovered the first of the methane brown dwarfs by accident while looking for the tell-tale signs of quasars -- giant objects in the distant regions of the universe.
 
The faint red light from the methane brown dwarfs drew his attention because it looked similar to the light expected from a quasar. But when he began looking closely at the data, he realized the object had important differences that meant it must be a nearby object, tiny and faint. Scientists had expected objects like methane dwarfs might exist in space -- indeed, one was discovered in 1995 orbiting a star.
 
But no one knew whether methane dwarfs could fly solo.
 
"We really didn't know whether these things would exist free-floating in space," Golimowski said.
 
How they got there remains a mystery.
 
The scientists say they could have been formed adjacent to a star and then flung out of orbit by a gravitational slingshot. Or they could have formed by themselves in empty space from a cloud of gas that collapsed under its own weight.
 
The light the telescope sees from the object is a remnant of the heat created in its formation, like the fading glow of a fireplace ember. The scientists don't know how far away the overgrown planets are. But methane dwarfs give off very little light, and so the fact that they can be seen at all indicates they must not be far away.
 
Golimowski estimated that they're within 30 light-years of Earth, an area in our neighborhood of the galaxy that contains perhaps 300 of the stars nearest to us.
 
"They have to be quite near," Fan said.
 
And because two have been found in just the small part of the sky already surveyed, it's likely that there are many more to be found, with the number likely similar to the number of stars in our neighborhood, Golimowski said.
 
Fan said the discoveries demonstrate the power of the new kind of astronomy embodied in the Sloan.
 
Instead of pointing at a single object an astronomer wants to study closely, the Sloan is slowly making its way across the entire sky, sucking up data on millions of objects.
 
The scientists involved can then use computers to study the attributes of large numbers of objects, looking for oddballs like Fan's and Golimowski's methane dwarfs, and also a better understanding of how the universe works. "We will be able to find rare objects," Fan said. "As we cover more and more sky, we're waiting for our mystery objects to show up."
 
"It gives us charts and plots and graphs, things we can sink our teeth into and really tell what the universe is like," said University of Chicago astronomer Constance Rockosi.





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