Super-Earth Discovered In Star's Habitable Zone

astroengine writes "The family of planets circling a relatively close dwarf star has grown to six, including a potential rocky world at least seven times more massive than Earth that is properly located for liquid water to exist on its surface, a condition believed to be necessary for life. Scientists added three new planets to three discovered in 2008 orbiting an orange star called HD 40307, which is roughly three-quarters as massive as the sun and located about 42 light-years away in the constellation Pictor. Of particular interest is the outermost planet, which is believed to fly around its parent star over 320 days, a distance that places it within HD 40307's so-called "habitable zone.""

Apostrophe!

[Dan East]

Star's, not stars', unless the planet is orbiting more than one star at a time. Didn't we just talk about apostrophe abuse in another Slashdot headline a couple days ago?

Habitable Planets might be rare

[l810c]

But what about moons?

We have found plenty of Jupiter size planets in the habitable zone.

Imagine a planet larger than Jupiter with 60 moons orbiting in the habitable zone. Many with liquid water.

I just marvel at the amount and diversity of moons in our own solar system. It seems like there would be far more moons in the habitable zone than planets universe wide.

Hopefully in the future we'll build some giant telescope and get a better answer.

Re:Fermi's p

[macraig]

So they'll leapfrog straight to quantum teleportation, then?

Re:Wake me up when they find a second earth

[belthize]

I see no real point in waking you up, not like you're going to contribute anything when we do.

Re:Habitable Planets might be rare

[wierd_w]

Just to play devil's advocate here.

Let's assume that we have a neptune sized gas giant going through its daily grind around its parent star, and that it has a magnetosphere. (Only 1 in 50 red dwarf systems have a jupiter mass object in orbit, but 1 in 3 has a neptune mass object.)

That close to its parent star, it would collect a tremendous amount of "cold" stellar plasma. (our little dirtball collects enough to create the van allen radiation belts. A neptune sized object would create a radiation torus MUCH larger.) This would inflate the magnetosphere to gargantuan proportions. This means that a great many of the proposed moons orbiting the gas giant would still retain thick atmospheres, unless other cosmic forces were actively at work to strip them. (like I think Enceladus's interaction with Saturn's magnetosphere...) Under such conditions, a rocky body like jupiter's moon Titan, which has a thick nitrogen and hydrocarbon atmosphere would be heated by both tidal heating, and be within the habitable zone. It would have an abundance of volcanic activity, and would get sufficient light that it could theoretically develop a biosphere.

If you throw into the mix all the red dwarf stars in our local star cluster, and the shockingly large number of detected gas giant planets we have detected so far in "inner" solar system orbits, a solution to the problem of potentially habitable bodies in red dwarf systems becoming tide-locked is provided by moons orbiting habitable zone gas giants. Such systems would be well protected from meteor impacts, as the gas giant would sweep the vast majority of objects out of the orbital path of the pair. The gas giant would keep the rotation and orbital period of the moon on a nice even keel, and would provide a strong magnetosphere.

If I were looking for a place to build a colony that could last a VERY VERY long time, I would look for goldilocks gas giants with habitable moons around red dwarf stars. The only niggly problem is the statistical scarcity of light elements like hydrogen in these systems. (M type stars are very rich in metals, but light on hydrogen and helium compared to more larger and more luminous stars. Any moons orbiting such gas giants are more likely to have an excessive amount of crustal oxygen than in other types of system, as metal oxide spectral lines are a mainstay feature of M type stars.) This might be resolvable if the system is "Absurdly old", as the high concentration of heavy elements would suggest a high level of radiological isotopes in the mineral composition of the planetary and satellite objects of such systems. This means that radiologically produced hydrogen from fission reactions over time could provide the missing hydrogen. M type star systems are quite capable of persisting to such advanced cosmic ages.

I would be very interested in the prospect of habitable satellites of massive objects in red dwarf systems, and think that planets like ours get too much attention in the search for habitable bodies.

Re:Fermi's p

[Endovior]

Good math, but you're ignoring the effect of mass on density. Earth is more dense than (for example) Mars because its greater mass results in more gravitational pressure, thus compressing its core, and increasing the density. There are limits, of course, and composition really does play a much bigger role than mass... hence why Mercury is the second densest planet in our system, despite being significantly less massive, and why gas giants have much lower densities, despite being vastly more massive. Even so, given that we don't know anything about the composition of this planet, odds are that since it's more massive than Earth, it'll have a higher density. How much higher would be pure speculation, of course, but because of that factor, I'd bet on a radius less than 1.9 Earths, and a gravity of more than 2 G.

Re:Water

[BeanThere]

The popular linguistic assumption/convention is that if water is not mentioned, it's probably absent.

Let's rather stick to avoiding ambiguity. Otherwise you just know the first person who goes to a planet and finds no water, is going to sue, and lawyers have enough money.