UF Astromers Part Of Team To Spot Possible Two-Star Solar System

April 21, 1998


GAINESVILLE --- In a discovery they say could shed new light on the genesis of our solar system, astronomers with the University of Florida and Harvard University have found a star surrounded by a disk of dust that may be forming planets.

"It's very exciting. We don't see planets directly in this system, but there is indirect evidence of a planet," said Charles Telesco, the astronomy professor leading the four-member UF team. He said a wake-like void that appears in the disk is typical of what would be left by a moving celestial body.

NASA is scheduled to announce the discovery at 11 a.m. Tuesday (4/21) at its headquarters in Washington, D.C.

The find, made in mid-March, marks the first time such a disk has been confirmed to exist around a binary, or two-star, system, Telesco said. A similar dust disk was discovered about 14 years ago surrounding a single star, Beta Pictoris.

"This may be the primordial dust that planets form from. These are the conditions that would have to be met for planets to form," said Scott Fisher, a UF graduate student who was part of the UF astronomy team.

The UF/Harvard team made its find at Cerro Tololo, Chile, using a telescope at an observatory belonging to the National Optical Astronomy Observatories. At almost the same time, another team comprising astronomers from Cal Tech/Jet Propulsion Laboratory and Franklin & Marshall College spotted it using an observatory on Mauna Kea, Hawaii.

Known as HR 4796A, the star is about 220 light years from Earth and about 47 billion miles from its companion star, HR 4796B. It is in the constellation Centaurus, visible primarily from the Southern hemisphere.

Astronomers estimate HR 4796A could represent what Earth's solar system looked like in its infancy, Telesco said. The sun is about 5 billion years old, and the earth is about 4.5 billion years old. The HR 4976 pair, by comparison, is estimated to be about 10 million years old, which Telesco said puts the dust disk precisely in the proper planet-building time frame.

"What we may be looking at is a solar system like our solar system but at a much earlier stage," Telesco said.

If the entire dust disk has formed planets or is forming them, the solar system would be considerably larger than our own. Measuring from Pluto, the planet farthest from the sun, our system is about 80 astronomical units across. The HR 4976 disk is more than three times that size -- some 250 astronomical units. An astronomical unit is the distance from the earth to the sun -- about 93 million miles. However, Telesco said, planets may be forming only near the inside edge of the disk, an area roughly the size of our solar system.

The teams have submitted documentation of their discovery to "Astrophysical Journal Letters," an astronomical professional journal. Funding for the project came from NASA, UF and the National Science Foundation.

The UF-built, mid-infrared array camera that made the images of the disk-star is known as OSCIR, which stands for Observatory Spectrometer Camera for the Infrared.

"The new generation of mid-infrared detectors is what made this discovery possible," said Telesco, whose team built the camera. "These sensitive cameras, when used on the world's best telescopes, will lead to an explosion of new results as exciting as the HR 4976 disk."

He predicts the discovery will be of major significance, both in the astronomy world as well as elsewhere. "This will become a very famous object, I guarantee you," he said. "Beta Pictoris is kind of a touchstone; HR 4976 doesn't have as poetic a name, but it's very pretty to me."

University of Florida

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