Scientists: Bulge could be planet larger than Jupiter

Sally Heap NASA

In this story:

• 'It's not too unreasonable'
• Nothing like 'us walking around'
• Dust in both systems similar

January 8, 1998
Web posted at: 11:29 p.m. EST (0429 GMT)

WASHINGTON (CNN) -- Scientists said Thursday that a bulge in the dusty halo of a star called Beta Pictoris may be the gravitational wake of a huge planet with the potential for primitive life.

New images made by the Hubble Space Telescope add weight to the theory that planets can develop outside our solar system, but some scientists say the bulge is not caused by a hidden planet, but by the pull from a passing star.

The pictures, taken by a new camera on the Hubble Space Telescope, focus on the disk or halo of dust and gas that rotates around Beta Pictoris, which is located in the southern constellation Pictor.

Instead of having a smooth flow, the disk has a large bulge in one quadrant.

NASA scientist Sally Heap said the bulge could only be shaped by the orbital path of a large planet, perhaps one many times larger than Jupiter, the largest planet orbiting the sun.

"We can't see it, but we can see the effects of its gravitational pull," Heap said at a news conference held by the American Astronomical Society.

Radio astronomy studies have suggested the presence of planets around more than a dozen other stars, but this is the strongest evidence yet in visible light of a possible planet. It adds to an earlier study that suggested planets were forming about Beta Pictoris.

'It's not too unreasonable'

Beta Pictoris has long fascinated scientists trying to determine what our solar system might have looked like before the planets formed.

For years, astronomers have looked to the star, a comparatively close, sun-like star 63 light years from Earth, as a possible site for the development of a planetary system. A light year is about 6 trillion miles, the distance light travels in a year.

But until now, they have referred to the dust surrounding this star as a protoplanetary disk, something that might develop planets sometime in the future.

But Heap, an astronomer with NASA's Goddard Space Flight Center in Maryland, said alternative theories -- notably that the bulge might be caused by the radiation from a neighboring star -- can be ruled out.

"We're left with the planetary hypothesis," she said. "It's not too unreasonable."

Fred Bruhweiler Catholic University

However, astronomer Fred Bruhweiler of Catholic University of America instantly disagreed.

Beta Pictoris is about 60 percent larger and between eight and nine times brighter than our sun, so any planet harboring life even vaguely analogous to that on Earth would have to be further away from Beta Pictoris than Earth is from the sun, Bruhweiler said.

Nothing like 'us walking around'

Any possible Earth-like planet would also have to have a thicker ozone layer to protect it from ultraviolet radiation, he said.

And Bruhweiler pointed out that the lifespan of Beta Pictoris is thought to be about 1 billion years, a relatively short time for life to develop.

"You might expect primitive life (on such a putative planet), but I wouldn't expect anything like us to be walking around," Bruhweiler said.

Heap said Beta Pictoris is 20 million to 100 million years old, just a fraction of the sun's 4.5 billion to 5 billion years. But despite its young age, said Heap, the star apparently already has planets forming. This suggests, she said, that planets form very early in the life of a solar system.

"When we study Beta Pictoris, it tells us things about how solar systems such as ours formed," she said.

Heap added that the young planet will never be seen from Earth because even if it exists, it would be expected to be shrouded by dust.

Dust in both systems similar

The case for a planet surrounding the star is strengthened by a study that found the dust in the Beta Pictoris disk is of the same composition as the dust found in comets in the solar system.

Whether the bulge actually is a planet could be resolved in the next 20 years, scientists say. Instruments are expected to be developed in the next 20 years that will not only pinpoint planets outside our solar system, but also determine whether they have atmospheres that could sustain life.

Correspondent Rick Lockridge, The Associated Press and Reuters contributed to this report.

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