Some more on that new planet, MOA-2007-BLG-192-L b

Monday, June 09, 2008

Over at there's some more information and theory (=speculation) on the new planet that was announced just a week or so ago. Thus far it's been stuck with the name MOA-2007-BLG-192Lb. Here are some interesting parts from the page (and the comments below):

(and by the way, the planet now has its own Wikipedia page though its host star doesn't have one yet)

The planet orbits its host star at about the same distance as Venus orbits the sun. But the new planet's host star is likely between 3,000 and 1 million times fainter than the sun, so the top of the planet's atmosphere is probably colder than Pluto.
The astrophysicists suggest the tiny planet supports a thick atmosphere, which along with possible interior heating by radioactive decay, could make the surface as balmy as that of Earth. (And theory suggests the surface may be completely covered by a deep ocean.)
I wrote a post on this subject before as well, that with a thick enough atmosphere and activity below ground a planet doesn't necessarily need to be located in a habitable zone to be warm and to have life.

More from the article:

The li'l planet — weighing in at three times Earth's mass ­— grabs the lightweight title from a five Earth-mass planet just announced in April.

The super-Earth is called MOA-2007-BLG-192Lb, after its host star MOA-2007-BLG-192L, which is located about 3,000 light-years from Earth. (A light-year is the distance light travels in one year, or about 5.88 trillion miles — 9.46 trillion kilometers.)

The host star's mass is estimated to be roughly 6 percent of the sun's mass, or just below the mass needed to sustain nuclear reactions in its core, thus making it a brown dwarf. Measurement uncertainty means the host mass could be slightly above 8 percent of a solar mass, which would make MOA-2007-BLG-192L a very low-mass hydrogen-burning star. The researchers suspect the star is indeed a brown dwarf.

"Our discovery indicates that that even the lowest mass stars can host planets," said lead researcher David Bennett of the University of Notre Dame. "No planets have previously been found to orbit stars with masses less than about 20 percent of that of the sun, but this finding suggests that we should expect very low-mass stars near the sun to have planets with a mass similar to that of the Earth."

and here's one of the comments I found to be particularly interesting:

Whether it's frozen or not will not be determined easily. However, to all there who cannot think of a hot planet below a blanket of H2/He: do not forget Uranus and Neptune!!! As a reminder Uranus/Neptune have a ultra-hot supercritical ocean of water/ammonia under their ultra-thick H2/He atmosphere. Take few thousands of degrees off and you get a liquid phase instead of the supercritical fluid! This is what you get with a smaller, hence colder version of Uranus. Think of it as an intermediate (and there is plenty of room inbetween!) between Uranus/Neptune and Pluto/Eris.

Such planets would be especially interesting as they should be quite common AND do not require any condition of distance wrt to a star for the open-air ocean to exist. Even a floating planet of this type could be interesting habitability-wise.

Even if it is now frozen btw (and this is doubtful if it has really the radiogenic energy of three Earth masses), it must have been liquid at a given time in the past for billions of years.

Unfortunately this star and its planet are way too far away to get too even if we were able to reach closer stars within a few light-years. This one is 3000 LY away. However, it's certain that we will be finding many more of these soon. Not much longer now.


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