Sunday, August 30, 2009

Exoplanet Incineration

If anything makes a planet a less promising candidate for colonization that orbiting so close to its parent star that the dayside hemisphere is heated to 2400 K, it is the prospect that said planet is on the brink of its final swan dive, about to plunge into the star. But that is just the spectacle that Sky & Telescope offers in its latest indulgence in gratuitous celestial violence.

The doomed planet, Wasp-18b, was never going to be a prime colonization spot at any distance from its stellar parent, since it is about 10 times the mass of Jupiter, only slightly below the 13 Jupiter mass lower limit for brown dwarfs. If it ever had moons it lost them when it migrated inward from where it formed (by current theory), beyond the 'snow line, to its present close orbit just 2.2 million km above the surface of the star Wasp-18 itself. This star is no red dwarf, but a sunlike star, class F6 (a bit hotter than the Sun), and about a billion years old.

Tidal forces should doom the planet in no more than a million years. Orbiting much faster than the star's period of rotation, it is tidally spinning up the star - and spinning itself down in the process, transferring its orbital angular momentum to the stellar parent that will presently dine on it. (Two myths for the price of one - Chronos eating his children and Icarus flying too close to the sun.)

The odds of us finding a planet so near to its final plunge are likened to the chances of drawing two red aces - rare, but not flukishly so. Which doesn't keep the article from indulging in a little pr0n about how All Our Theories Could be Wrong. But a doomed planet is not all that unlikely, and a lot more fun.


Related links: I recently contemplated the demise of Betelgeuse, and colliding protoplanets.

11 comments:

Anonymous said...

Another spectacular sight we probably will miss seeing...

Ferrell

Rick said...

But if we keep looking, sooner or later we'll see something spectacular.

Jean Remy said...

I hope it's not very spectacular and very close at the same time. I'm allergic to massive planetary obliteration.

Roadtripper said...

Most people are, Jean. But think of what we could learn!

http://www.theonion.com/content/news/scientists_warn_large_earth

Anonymous said...

Sounds like a Space Opera tourist trap - Watch Wasp-18b plunge into its star right after visiting the Krypton Wastes.

Ian_M

Anonymous said...

"Sounds like a Space Opera tourist trap - Watch Wasp-18b plunge into its star right after visiting the Krypton Wastes."
HAHAHAHA! I can see the creation of interstellar travel simply to let tourists see some poor planet be destroyed in a spectacular fashion...

Ferrell

Anonymous said...

"The methane atmosphere flares so beautifully as it's ignited by the star's heat... Oh bartender, another Krimson Kryptonite please. Make it a double."

On a less silly note, yet again the real world proves to be far less orderly than we originally thought. Whatever happened to the Titius-Bode Law?

Ian_M

Rick said...

Belatedly (because I've been buried in numbers; see new post), wonderful comments!

And yes, what DID happen to Bode's Law?

Jean Remy said...

Oh and in related news, we didn't land on the Moon apparently.

http://www.theonion.com/content/news/conspiracy_theorist_convinces_neil

Well there goes space tourism.

Rick said...

Jean - the URL was truncated, but enough for me to guess the story. :-)

The scary thing is that there really are moon landing conspiracy theories out there.

Jean Remy said...

Should work as typed, actually.

Those conspiracy theorists provide hours of endless entertainment.