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

[Aighearach]

seven times more massive than Earth...

so much for their early space program

And the green alien sex.

Re:Fermi's p

[wierd_w]

Assuming they use extensible appendages for locomotion at all.

At that level of local gravity, they are more likely to be something like a gastropod, or aquatic.

pumping blood under 7 Gs is something human hearts require a pressure suit for! Any large bodied creatures from that planet would have to have a very different anatomic makeup from ours.

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

[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:Fermi's p

[symbolset]

A planet like that almost certainly has a moon of the correct size and composition. When we get to the stars we will find that almost all have homes for Men.

Re:Fermi's p

[Jane Q. Public]

Not so much. They say it's rocky and roughly liquid-water distance so it's probably close to Earth density, which limits the diameter. Spin rate might affect the perceived gravity but because of other factors is probably not very much of an issue.

Most likely, surface gravity would be roughly 3 times Earth gravity.

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

[Spottywot]

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

Maybe, or maybe they just develop different tech, space elevator maybe?

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.

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?

Re:Apostrophe!

[Crypto Gnome]

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?

No, I'm pretty sure it was Child Abuse.

Re:Apostrophe!

[Tukz]

Potato, tomato.

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:Habitable Planets might be rare

[mcgrew]

Small planets don't fair that well

Well, sure they do. We have two state fairs in Illinois, plus a fair for every county. It's probably like that in most states, and probably every country has a few good fairs. So I'd say Earth fairs VERY well.

As to the moon, there are no fairs on the moon but it fares pretty well where it's sitting.

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.

No problem

[Sussurros]

Just hit the little button on the back of the Sontarans' helmets and they go down like a sack of potatoes.

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.

"So-called", it IS the Habitable Zone!

[felixrising]

What's with the poor "Habitable Zone" being "So-Called"? That makes it sound like it's not the correct name for it, but being the correct scientific term, how can it be incorrect? Okay, maybe it's the "Circumstellar Habitable Zone", but come on!!! It IS the theoretically "habitable zone" of a parent star, you could call it the so-called "Goldilocks Zone", because the phase "Goldilocks Zone" is just colloquial. /me ends rant.

Re:"So-called", it IS the Habitable Zone!

[Black Parrot]

What's with the poor "Habitable Zone" being "So-Called"? That makes it sound like it's not the correct name for it, but being the correct scientific term, how can it be incorrect? Okay, maybe it's the "Circumstellar Habitable Zone", but come on!!! It IS the theoretically "habitable zone" of a parent star, you could call it the so-called "Goldilocks Zone", because the phase "Goldilocks Zone" is just colloquial. /me ends rant.

I think "Goldilocks zone" is actually better, because it's the zone that's "just right". "Habitable" isn't a boolean proposition everywhere.

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:We should probably hurry and try to get there

[symbolset]

In our own solar system we have entire moons made entirely of hydrocarbons. No need to go to another star for that.

Jinx?

[roc97007]

Just sayin'...

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: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.

Re:too heavy

[Electricity Likes Me]

That said, the lack of radiation could very well make advanced life unlikely, given the effects it'd have on mutation rate.

The effects of radiation on genetic mutation are largely unknown. We have (in fairly recent years) discovered that genetic mutation can and does occur from environmental factors other than radiation. It's a huge unknown, so to be blunt it's equally likely that the reduced radiation could actually lead to more stable mutations and an overall increased evolution rate.

I'd like to be even more specific: you don't need radiation for genetic mutation to occur. Standard DNA polymerases make mistakes all the time without any outside forces beyond thermodynamics, and simple viruses like Ebola tend to have very poorly performing RNA polymerases that make a lot of mistakes because it's advantageous to their survival to do so.

Conversely, bacteria that live in fuel rod settling pools take the opposite approach - they "staple" their DNA together with a high GC content to improve radiation resistance. There's such a diverse range of factors at play that it's ridiculous to suggest "radiation" would give us any information about whether a place could have advanced life.

42 light years

[TyFoN]

Maybe the answer is 42 :)
BUT.
42 light years at 10% of the speed of light (which is within the possibilities) and it would only take about 10 generations to reach this place.
It could actually be a place suitable for evacuation!

Re:42 light years

[Metabolife]

Who would want to spend their entire life in a small room surrounded by their parents? Oh wait.. this is /.