Several Jupiter sized planets found to have only weak Earth like gravity

May 02, 2007
Several Jupiter sized planets found to have only weak Earth like gravity

Astrophysicists at the University of Warwick have found that several Jupiter sized gas giants beyond our solar system have surface gravities much closer in strength to Earth than the intense gravity of Jupiter.

The University of Warwick team , Dr John Southworth, Dr Peter Wheatley and Giles Sams are the first people to calculate accurate measures of the surface gravity of all 14 known gas giant planets beyond our solar system that can be observed transiting (moving across the face of) their star.

They created a new method which enabled the Warwick researchers to deduce the surface gravity of all 14 of these gas giants using a technique which is both simpler and ten times more accurate than an older method that had only produced a rough estimate for just one of the gas giants - HD 209458.

All but one of these 14 known gas giant planets that can be seen transiting their star have a planetary radius bigger than Jupiter. Intriguingly the one older surface gravity estimate available, for HD 209458, suggested it had a surface gravity of only 9.43 to 9.7 ms-2. Despite being bigger than Jupiter this would give it a surface gravity closer to Earth’s at 9.8 ms-2 or our own solar system’s smaller gas giants (Saturn 8.96 ms-2, Uranus 8.69 ms-2 and Neptune 11.15 ms-2) rather than Jupiter at 24.79 ms-2.

On carrying out their more accurate measurement of all 14 of these gas giants the Warwick team have discovered that the surface gravity of HD 209458 is not an anomaly. Despite all but one of the gas giants (HD 149026) being bigger than Jupiter all but one of them turned out to have surface gravities that are much lower than Jupiter’s. Only OGLE-TR-113 was found to have a surface gravity higher than Jupiter’s.

In fact they found that 4 of these planets actually have surface gravities close to or lower than that of Earth’s or our own solar system’s "smaller" gas giants rather than Jupiter’s much more intense gravity. A further 4 had surface gravities around half to two thirds that of Jupiter’s. For the planet for which there was already a rough estimate of surface gravity (HD209458b) they actually found an even lower surface gravity of 9.28 ms-2 (error factor of plus or minus 0.15 ms-2).

University of Warwick researcher John Southworth said: "This research gives us a sense of the sheer variety of types of planet to be found beyond our Solar System. An understanding of the surface gravity of these worlds also gives us a clearer picture of the rate of in the evaporation of planetary atmospheres."

Full paper online at uk.arxiv.org/PS_cache/arxiv/pd… 0704/0704.1570v1.pdf

Source: University of Warwick

Explore further: New space telescope concept could image objects at far higher resolution than Hubble

add to favorites email to friend print save as pdf

Related Stories

Getting to know Rosetta's comet

18 hours ago

Rosetta is revealing its host comet as having a remarkable array of surface features and with many processes contributing to its activity, painting a complex picture of its evolution.

Rosetta data give closest-ever look at a comet

Jan 22, 2015

On Nov. 12, 2014, the European Space Agency's Rosetta mission made history when its Philae lander touched down on the surface of comet 67P/Churyumov-Gerasimenko. While this exciting technical achievement ...

Scientists look for what's causing Texas earthquakes

Jan 14, 2015

Swarms of small quakes rippled up from unknown faults beneath the soil. They rustled Cleburne, Azle and Irving. Fifteen recent earthquakes around the old Texas Stadium in Irving site included the strongest yet in Dallas County, ...

Why is Venus so horrible?

Dec 19, 2014

Venus sucks. Seriously, it's the worst. The global temperature is as hot as an oven, the atmospheric pressure is 90 times Earth, and it rains sulfuric acid. Every part of the surface of Venus would kill you ...

Recommended for you

Chandra celebrates the International Year of Light

Jan 23, 2015

The year of 2015 has been declared the International Year of Light (IYL) by the United Nations. Organizations, institutions, and individuals involved in the science and applications of light will be joining ...

Why is Andromeda coming toward us?

Jan 23, 2015

I don't want to alarm you, but there's a massive galaxy heading our way and will collide with us in a few billion years. But aren't most galaxies speeding away? Why is Andromeda on a collision course with ...

The cosmic chemistry that gave rise to water

Jan 22, 2015

Earth's water has a mysterious past stretching back to the primordial clouds of gas that birthed the Sun and other stars. By using telescopes and computer simulations to study such star nurseries, researchers ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.