News > Geek > On the Annihilation of Stars that Might Have Been

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THURSDAY DECEMBER 6 2007 8:00 AM

On the Annihilation of Stars that Might Have Been

When I saw that space dot com had an article out called "How to Destroy a Giant Planet," I got really excited in an "I hope no nefarious super-villians are reading this" sort of way. As it turns out, it's coming from an angle not involving dynamite or hordes of zombie minions, but nevertheless it's still quite an informative little essay if you're interested -- not a manual on grand-scale demolition so much, but a study in the structural evolution of gas giants, and the sort of extremes that might have led to these planets' own demise.

The gas giants are apparently something more of a mystery than other bits of our solar system. We have a good handle on how stars are formed, after all, and the concrete inner planets like our own are relatively straightforward, but our colder and more distant satellites are caught somewhere in between. According to a team of researchers at University College London, that very distance is really all that keeps them held together.

We know that Jupiter has a thin, stable atmosphere and orbits the sun at 5 Astronomical Units (AU)or five times the distance between the sun and the Earth," explained UCL's Tommi Koskinen. "In contrast, we also know that closely orbiting exoplanets like HD209458bwhich orbits about 100 times closer to its sun than Jupiter doeshas 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...
"If you brought Jupiter inside the Earth's orbit, to 0.16AU, it would remain Jupiter-like, with a stable atmosphere," Koskinen said. "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."

In summary, the closer you bring a planet like Jupiter to the actual sun, the more likely it is to no longer exist. Which would be, one would think, pretty much the same response as everything else in the galaxy. The interesting thing is that the researchers say it wouldn't burn up (the bane of all these tiny stars that never ignited) so much as evaporate. Why is that? Loss of atmosphere, they say. It's not happening with our friendly neighbor planets, thanks to distance, but many are watching it happen on aforementioned and ungainly-named HD209485b, which orbits so close to its own sun that a year takes only three and a half days.

According to a group of U.S. astronomers, data from the Hubble Space Telescope show how intense ultraviolet radiation from the host star heats the gas in the planet's upper atmosphere, inflating it like a balloon. The gas becomes so hot and energetic that it escapes the planet's gravitational pull, blasting out into space at a rate of nearly 10,000 tonnes per second - more than three times the rate of water flowing over Niagara Falls. The escaping gas gives the planet a tail, said the team.

The UCL researchers mentioned a magic number, a safe distance of 0.15 Astronomical Units. Anything closer seems to affect the level of hydrogen in the planets' atmosphere, creating something like a hole-in-the-ozone effect -- except that, in this case, air gets sucked out of that hole in the atmosphere like an airplane with a window kicked in.

A giant planet is cooled by its own winds blowing around the planet. This helps keep the atmosphere stable. Another cool effect: An electrically-charged form of hydrogen called H3+ reflects solar radiation back to space. As the virtual Jupiter was brought closer to the sun, more H3+ was produced, bolstering this cooling mechanism.

"We found that 0.15AU is the significant point of no return," said study co-author Alan Aylward. "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."

It's just a little more insight into the way our galaxy works, which is always pretty fascinating. Let's just hope there are no evil scientists reading this: with a few improbable billion dollar planet-moving tools, who knows what sort of malarkey could be done, now that you know how to evaporate a planet.

_DictionaryGirl_ will so call the X-Men on you, so seriously, don't even think about it.

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Comments

Tony_T

San Diego, CA

August 2005

DEC 06, 2007 08:43 AM

Our universe fascinates me to no end.

The Hubble observations revealed oxygen, carbon, and sodium in HD 209458b's atmosphere, as well as a huge amount of hydrogen in its upper atmosphere. The escaping gas comes from only this top-most layer, said research team leader Gilda Ballester, of the University of Arizona in Tucson. "The layer we studied is actually a transition zone where the temperature skyrockets from about 727° C to 14,727° C - which is hotter than the Sun," she said.

thedragonjedi

Aurora, IL

April 2007

DEC 06, 2007 08:50 AM

Damn Right it is. It's completely mindboggling when considering how expansive our universe is. Most would like to feel as if it stops at some point but It would blow your mind to realize there is no end to our universe. I guess we will never find that restuarant at the end of the universe. I hear it's quite good.

Spica

SUICIDEGIRL

I'm lost

DEC 06, 2007 09:16 AM

dragonflower

Austin, TX

January 2007

DEC 06, 2007 09:46 AM

thanks, DG, i'd heard of this before, but not read much on it.
more astronomy pls?!

ZenTrixter

Portland, OR

October 2002

DEC 06, 2007 09:53 AM

But Alderaan is a peaceful world...

bean

STAFF

Los Angeles, CA

DEC 06, 2007 09:56 AM

Tony_T said:

"The layer we studied is actually a transition zone where the temperature skyrockets from about 727° C to 14,727° C - which is hotter than the Sun," she said.

Whoa.

Another great article, DG. Your stuff is always a pleasure to read.

bean

STAFF

Los Angeles, CA

DEC 06, 2007 09:59 AM

Oddly, I was just listening to Last.fm's recommeded radio, and IMA Robot's "Cool Cool Universe" just came on. Hehe.

O_star

I'm lost

December 2004

DEC 06, 2007 10:31 AM

Yeah, no one was expecting to find all these huge planets near stars - the so called hot-jupiters - but they were the first kind to be discovered. That's becuase the two main methods for planet discovery these days - the doppler or 'wobble' method and the transit of eclipse method - both favor big things near to the star.

But still, it is weird that there are all these big things so near to the stars, and all of planet formation theory has had to be rearranged to accomodate them.

It's a crazy time for planets!

d20

San Francisco, CA

September 2003

DEC 06, 2007 10:33 AM

this article caused a serious mid-morning chromatics binge.