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.""

Comments

Fermi's p

[harvey the nerd]

seven times more massive than Earth...
so much for their early space program

Re:Fermi's p

[NEDHead]

Depends on the diameter and the rate of rotation.

Re:Fermi's p

[macraig]

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

Re:Fermi's p

[rossdee]

Just as well, because if they ever did get off their planet they would be able to beat us.
(their ships would out maneuver ours , they would have faster reflexes, and we wouldn't have a chance in hand to claw combat

Re:Fermi's p

[feedayeen]

seven times more massive than Earth...

so much for their early space program

Assuming 2 planets have equal densities, Mass increases proportional to R^3, but gravity is proportional to the inverse squared of the distance.... As a result, surface gravity increases only linearly with the radius.... in this case, the planet would have 1.9 times the radius of the Earth if it's the same density.

Earth has a very high density actually at 5.5g/cm3, it's actually the densest planetary object in our solar system. Most terrestrial objects are closer to 2 and the larger ones tend to be 3. It is entirely possible that it'll have a comparable surface gravity.

Re:Fermi's p

[Sperbels]

Just as well, because if they ever did get off their planet they would be able to beat us. (their ships would out maneuver ours , they would have faster reflexes, and we wouldn't have a chance in hand to claw combat

Would they? Maybe their biochemistry makes it more efficient for them to have extremely slow reflexes. Maybe their movements would be as fast as grass growing. We could round up their entire invasion force and give them all anal probes and alien autopsies before they even knew what happened.

Re:Fermi's p

[Bill Currie]

No, his math is quite correct: M=d*4*pi*r^3, so M(p)/M(e) = (d*4*pi*r(p)^3)/(d*4*pi*r(e)) which simplifies to r(p)^3/r(e)^3, or (r(p)/r(e))^3, thus the ratio is the cube-root of 7: 1.913 (or 7.1: 1.922). Still, 2G would be a cow for us.

Re:Fermi's p

[Anonymous Coward]

We could round up their entire invasion force and give them all anal probes and alien autopsies before they even knew what happened.

I find your ideas intriguing and would like to subscribe to your newsletter.

Re:Fermi's p

[tgd]

Just as well, because if they ever did get off their planet they would be able to beat us.
(their ships would out maneuver ours , they would have faster reflexes, and we wouldn't have a chance in hand to claw combat

And worst of all, their muscles are probably so dense, no amount of slow roasting will bring out any real flavor.

Re:Fermi's p

[dkf]

Solids and liquids are not significantly compressible.

While you're correct that they're a lot less compressible than a gas, you most certainly can still compress solids and liquids if you press hard enough. There's a lot of pressure inside the core of a planet...

Re:Fermi's p

[NEDHead]

Your math is a little off. If the density were the same as Earth's, the diameter would be proportional to the cube root of the mass ratios, or slightly less than 2 times that of Earth. The surface gravity is proportional to mass (7x) and inversely so to the square of the radius (~1/4) so 7/4 is about 1.75 surface gravity compared to Earth. If there were a comparable 'day' length, then the velocity at the equator would be about 2x that of Earth. An extra 1000 mph liftoff boost vs 1.75 local g, not so hard to overcome.

And since we know nothing about the planet other than the mass, this is all silly speculation.

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: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:too heavy

[MyLongNickName]

Earth masses is not the same as surface gravity. Assuming a similar density, this planet would have roughly twice the gravity as Earth.

Re:Water

[MyLongNickName]

No, we can't. The reading population is not static and I don't see how including it hurts anyone.

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:Wake me up when they find a second earth

[feedayeen]

He's just waiting for us to find something 80% N2 and 20% O2 with 70% of it's surface covered in water before he unveils his warp teleporter.

Re:Direct imaging!?

[feedayeen]

Taking pictures of bodies like Pluto isn't hard because it's far away from us, it's hard because it's far away from a light source and receives 1/2000th the illumination of the Earth, being small and far doesn't help, but that's not our big problem. Given that it's in the habitable zone, the amount of light should be comparable to that of the Earth, not something and given the expected surface area is nearly 4 times larger than that of the Earth's, it should be a quite bright pixel.

Re:Apostrophe!

[Tukz]

Potato, tomato.

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.