Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The fine line between stability and instability - when do gas giants reach the point of no return?

06.12.2007
Planetary scientists at UCL have identified the point at which a star causes the atmosphere of an orbiting gas giant to become critically unstable, as reported in this week’s Nature (December 6).

Depending upon their proximity to a host star, giant Jupiter-like planets have atmospheres which are either stable and thin, or unstable and rapidly expanding. This new research enables us to work out whether planets in other systems are stable or unstable by using a three dimensional model to characterise their upper atmospheres.

Tommi Koskinen of UCL’s Physics & Astronomy Department is lead author of the paper and says: “We know that Jupiter has a thin, stable atmosphere and orbits the Sun at five Astronomical Units (AU) - or five times the distance between the Sun and the Earth. In contrast, we also know that closely orbiting exoplanets like HD209458b - which orbits about 100 times closer to its sun than Jupiter does - has a very expanded atmosphere which is boiling off into space. Our team wanted to find out at what point this change takes place, and how it happens.

“Our paper shows that if you brought Jupiter inside the Earth's orbit, to 0.16AU, it would remain Jupiter-like, with a stable atmosphere. But if you brought it just a little bit closer to the Sun, to 0.14AU, its atmosphere would suddenly start to expand, become unstable and escape. This dramatic change takes place because the cooling mechanism that we identified breaks down, leading to the atmosphere around the planet heating up uncontrollably.”

Professor Alan Aylward, co-author of the paper, explains some of the factors which the team incorporated in order to make the breakthrough: “For the first time we’ve used 3D-modelling to help us understand the whole heating process which takes place as you move a gas giant closer to its sun. The model incorporates the cooling effect of winds blowing around the planet - not just those blowing off the surface and escaping.

“Crucially, the model also makes proper allowances for the effects of H3+ in the atmosphere of a planet. This is an electrically-charged form of hydrogen which strongly radiates sunlight back into space and which is created in increasing quantities as you heat a planet by bringing it closer to its star.

“We found that 0.15AU is the significant point of no return. If you take a planet even slightly beyond this, molecular hydrogen becomes unstable and no more H3+ is produced. The self-regulating, ‘thermostatic’ effect then disintegrates and the atmosphere begins to heat up uncontrollably.”

Professor Steve Miller, the final contributing author to the paper, puts the discovery into context: “This gives us an insight to the evolution of giant planets, which typically form as an ice core out in the cold depths of space before migrating in towards their host star over a period of several million years. Now we know that at some point they all probably cross this point of no return and undergo a catastrophic breakdown.

“Just twelve years ago astronomers were searching for evidence of the first extrasolar planet. It’s amazing to think that since then we’ve not only found more than 250 of them, but we’re also in a much better position to understand where they came from and what happens to them during their lifetime.”

David Weston | alfa
Further information:
http://www.ucl.ac.uk

More articles from Physics and Astronomy:

nachricht NASA's James Webb Space Telescope completes final cryogenic testing
21.11.2017 | NASA/Goddard Space Flight Center

nachricht Previous evidence of water on mars now identified as grainflows
21.11.2017 | US Geological Survey

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Previous evidence of water on mars now identified as grainflows

21.11.2017 | Physics and Astronomy

NASA's James Webb Space Telescope completes final cryogenic testing

21.11.2017 | Physics and Astronomy

New catalyst controls activation of a carbon-hydrogen bond

21.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>