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Absent Jupiters make dusty solar systems

Kuiper belt

Planetary systems with only low mass planets may have bigger Kuiper Belts than systems like ours which have giant gas planets (Source: NASA)

Dust collectors Planetary systems without giant gas planets like Jupiter tend to have more comets, according to two new studies.

The new discoveries may help scientists develop new criteria in their search for Earth like planets with liquid water and possibly life.

University of New South Wales astronomer, Dr Jonti Horner who worked on both studies, to be published in the Monthly Notices of the Royal Astronomical Society and Astronomy and Astrophysics, says the findings will help pick the best targets to focus on.

"Systems which have planets are also likely to have cometary disks like the Kuiper belt, a reservoir of frozen asteroids, comets and icy debris beyond the orbit of Neptune at the solar system's edge," says Horner.

"These debris disks are the material left over from planetary formation."

Last year, astronomers using the European Space Agency's Herschel space telescope found one of these debris belt surrounding the star Fomalhaut. These recent discoveries add Gliese 581 and 61 Virginis to the list.

According to Horner, the dust detected in each system is at least 10 times greater than in the Kuiper Belt surrounding our solar system.

Gliese 581 is located about 20 light years away in the constellation of Libra and is known to have at least four planets. One of these planets resides in the 'Goldilocks Zone', the distance from the star where liquid surface water could exist.

The other star, 61 Virginis, is less massive than the Sun and located about 28 light years away. It is known two have at least two planets.

Are we normal?

None of the known planets in either system are larger than Neptune, ranging in size from two to 18 times the mass of the Earth.

According to the researchers this suggests that an absence of Jupiter-sized planets results in much denser dust belts. This could mean more water available for the orbiting planets, but a higher likelihood of devastating impact.

Horner says current knowledge of planetary systems is based on our detailed mapping of our own solar system, which he says makes it difficult to understand.

"So we're bogged down in the minutia trying to explain where every single object came from," he says. "That makes it very hard to model how our planetary system formed and developed."

"When we look other systems we've got a simpler picture so you can see the broad brush strokes rather than the fine detail."

"This will help us find out how normal our solar system really is," says Horner. "Does it have more debris, comets and asteroids than normal which could have delivered water to a planet, or does it have less?"

"This could also be tied in to why Earth is only impacted occasionally by objects like the one that killed the dinosaurs."

Tags: planets-and-asteroids