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Astronomers Claim Discovery of Earth-like Planet
Raver32 writes "A team of astronomers announced they have discovered the smallest and potentially most Earth-like extrasolar planet yet. Five times as massive as Earth, it orbits a relatively cool star at a distance that would provide earthly temperatures as well, signaling the possibility of liquid water. 'The separation between the planet and its star is just right for having liquid water at its surface,' says astronomer and team spokesperson Stephane Udry of the Observatory of Geneva in Versoix, Switzerland. 'That's why we are a bit excited.' But researchers do not yet know if the planet contains water, if it is truly rocky like Earth, which might make it hospitable to life as we know it, or whether it is blanketed by a thick atmosphere. 'What we have,' Udry says, 'is the minimum mass of the planet and its separation" from its star.'"
That's only if the radius from the centre of the objects is the same. Remember, gravity decreases as a function of the square of the distance.
Anthropic principle: We see the universe the way it is because if it were different we would not be here to see it.
TFA is dated 24 April, 2007 -- I'm pretty sure that this is old news.
I wonder how long before we can verify an earth like extrasolar planet?
As more of these are found we may be able to plug more data into drake's equation
For you maybe, but anything that evolved in that environment would be really strong on this planet, be able to leap...wait, what was the name of that planet?
Can you imagine the women, why they'd be build like a brick shi...cue the Commodores.
Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong fix.
Mass alone says very little about the surface gravity of a planet - you need to know the radius of the object to make any statement about its surface gravity. Earth's moon has slightly over a percent of the mass of Earth, but about 1/6g surface gravity. Mars has only about 10% of the mass of Earth, while having 1/3g surface gravity.
I think that in planetary terms we can safely assume 5x mass will create an environment of roughly 5g ... maybe give or take 20%. Enough to ensure that the simple act of getting out of bed would be a gruelling ordeal.
Another problem I noticed after actually reading TFA:
Gliese 581 c, orbits at one fourteenth the distance between Earth and the sun. But the red dwarf is 50 times cooler than the sun. The group estimates that the planet would experience temperatures in the zero-to-40-degree-Celsius (32-to-104-Fahrenheit) range.
It is my understanding that red dwarfs, while generating reduced heat and light output, produce solar flares that are almost as intense as those produced by a G class star. So if a planet exists in the habitable zone it is also exposed to periodic sterilizing blasts of charged particles.
Maybe if we're lucky the planet happens to have a really strong magnetic field ... then we just have the crushing g load to contend with.
If libertarians are so opposed to effective government, why don't they all move to Somalia?
From the blurb itself, it's five time the size of earth, it's revolving around a cooler sun than earth, and it might not have liquid water or a thick atmosphere. Yeah, that's exactly like earth!
You're missing the point. By Earth-like they mean telluric planet, as in, not a gas giant. That's all. And that matters because until now we haven't found so many of them, most of the planets we've found were gas giants orbiting close to their star. But as time goes by we find ever decreasingly large planets that get closer and closer to the Earth in size.
You just got troll'd!
Andy
You're probably thinking of the shell theorem, which says that a uniform sphere of mass is gravitationally equivalent to a point mass located at the center of the sphere. This theorem does imply that a larger radius = less gravity at the surface.
Visit the
Plus you can take into account all the other advantages life on Earth has had to make it possible:
- In a solar system with a large gas giant, which helps keep catastrophic impacts with asteroids and comets from happening too often
- Has a large satellite, which may help stabilize climate
- Is in a quiet part of the galaxy, and is not too near other stars, avoiding interactions with other stars/gamma ray bursts/etc.
Invade!
--- What?
To calculate the gravitational effect of a massive sphere, its whole mass can be
:-)
considered accumulated in its center as long as you are outside of it.
So the gravitational acceleration indeed only depends on mass an distance.
Mathematical fact.
Neat additional trivia:
- Inside a hollow sphere, there is no gravitational effect by the sphere's mass - it cancels out exactly.
That's why
- Inside a massive sphere, gravitational acceleration increses linearly with the radial distance to the center.
(the mass increases with r^3 as you get further out, its effect decreases by 1/r^2 - and as it can be considered
concentrated in the middle, you get an increase by a factor of r^3/r^2 = r
Gravity is fun
All this of course only for constant density.
That's kind of important, I would think.
``No, we can even measure how surface gravity varies from g=9.78 m/s2 to g=9.82 m/s2 when moving from the equator towards a pole. And this is because Earth is not perfectly round, the people at higher latitudes are closer to the center of Earth and fall faster.''
No, that's because they drink more alcohol there.
Please correct me if I got my facts wrong.
The odds against it happening elsewhere are ... well ... astronomical.
The universe contains a very large number of elsewhere.
I think that in planetary terms we can safely assume 5x mass will create an environment of roughly 5g ... maybe give or take 20%. Enough to ensure that the simple act of getting out of bed would be a gruelling ordeal.
I don't know about you, but getting out of bed is a grueling ordeal at any gravity for me!
Yeah, that's an unreasonable density, but you should bear in mind that compression occurs. (Earth's uncompressed density is significantly lower than the actual density, for example.)
That said, you can fairly assume that the density is nearly the same as Earth's. In that case, the surface gravity is only about 70% higher than here. It'd still be tough walking around.
I think that in planetary terms we can safely assume 5x mass will create an environment of roughly 5g ... maybe give or take 20%. Enough to ensure that the simple act of getting out of bed would be a gruelling ordeal.
Another problem I noticed after actually reading TFA:
No, it would not. It would need to be much denser than Earth for that to happen. This is basically impossible for an object of that mass.
Assuming roughly Earth like density (which is quite plausible), Radius will scale like Mass to the 1/3, while gravity scales like mass / radius squared. This works out to about 1.7 times Earth gravity at the surface.
When they say "nearly the size of earth" they're speaking in an astronomical scale, which would qualify something 5-times as large as the earth as 'nearly'. It's not composed of gold or other heavy metal.
!#&*
Oh for god's sake, people! Do a little math.
Let's assume that the average density of the earth-like planet is the same as Earth. (It wouldn't be an earth like planet if it were significantly different.) Then we can use the volume of the sphere to relate the mass and the surface radius. Since M = 4/3 * \pi * R^3 * \rho, where \rho is the density, it is easy to see that the surface radius goes like the cube root of the mass. Putting this into Newton's equation, we can see that a = GM/R^2 means that the surface gravity is also going to go like the cube root of the mass. If the mass is five times that of Earth, then the surface gravity will be the cube root of 5 greater than Earth's or about 1.7 times Earth normal.
Taking differences in the mean density into account is no more difficult, but I leave that as an exercise for the reader.
It's a poorly written and shite article, but the box off to the side says:
One of two newly discovered exoplanets is nearly the size of Earth...
So, assuming they're talking about the same one, it should be roughly 5 times our gravity.
Not so. If the planet has twice the diameter of earth, that falls well within the category of "nearly the size of Earth" for astronomers. Since gravity decreases proportionally to the square of the distance, gravity would be only 5/(2^2) times as strong as on Earth, an increase of a mere 20%.
If it has approximately the same density as earth, then since volume of a sphere increases proportionally to the cube of the radius/diameter, it would have 5^(1/3) times as large a diameter as earth, which is about 1.71 -- even closer to the size of our Earth. It would also wind up with gravity 1.71 times as strong, since 5/((5^(1/3))^2) == 5/(5^(2/3)) == 5^(1/3).
I think that in planetary terms we can safely assume 5x mass will create an environment of roughly 5g ... maybe give or take 20%.
How do you justify that remark? Mars has a mass 1/9 of Earth's but a surface gravity over 1/3 of Earth's. Mercury has a mass 1/18 that of Earth but has gravity slightly higher than that of Mars.
There's just no way you can have confidence within 20% that the gravity will be proportional to the mass.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
If it's less than 14 Earth masses it's rocky. Simple as that ;-)
You just got troll'd!
"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is." ...and thats the thing about a really big place- sheer size provides an astronomical number of opportunities for such astronomically unlikely things to happen, over and over agin.
!#&*
Says you.
We don't know what it's composed of, and it *could* be solid gold. It *could be* heavy metal.
I personally believe it's composed entirely of soft rock. Chances are very slim that it's composed of top-40 pop or country&western.
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
Uncompressed density = density of material at 1 atm
Compressed density = density of material under given pressure
If we took all the stuff Earth is made of, took it apart and measured the average density of all those rocks at 1 atm, we would get a significantly lower average than what we get by dividing the estimated mass of Earth by its estimated volume.
Those who would give up liberty to obtain working drivers, deserve neither liberty nor working drivers.
you're both missing the point, if the planet has water, then the only factor is compression ratio, aquatic life don't suffer from gravity like land bound creatures do, if they have neutral buoyancy the only effect of gravity they feel is the relative pressure of the water at the depth they live in.
considering there are whales that can go very deep in the ocean, to the very surface, the pressure regulation seems to be easily solved.
gravity only becomes an issue when life tries to evolve from aquatic life to land based life.
without oceans the planet won't develop enough diversity of life to populate the land. and it's far enough away that we can't tell if it has oceans.
https://www.gnu.org/philosophy/free-sw.html
No, no, no. Fill it with hairdressers, tired TV producers, insurance salesmen, personnel officers, security guards, management consultants, and telephone sanitizers.
In this paper there are theoretical relations between planet radius and mass for a wide range of possible planet compositions. These are computed using equations of state that are largely determined from laboratory experiments.
Anyway, for an Earth-like composition (~67% rock, 33% iron), a 5 M_earth planet would have a radius of ~1.5 R_earth yielding a surface gravity that is ~2.2 times greater than that of the Earth (such a planet is not incompressible, so the density is slightly higher for a greater mass).
For a pure iron planet, the radius would be only 1.2 times that of the Earth and the surface gravity would be quite high (3.6 times the Earth's).
For a pure rock planet, the radius would be 1.7 times that of the Earth and the surface gravity would be 1.75 times that of the Earth.
For a pure "water-world" (say a scaled up version of some of the icy satellites orbiting the outer planets), the radius would be ~2.5 times that of the Earth and the surface gravity would be 0.8 times that of the Earth (i.e. less surface gravity than the Earth!).
Point is there is a fairly significant range in possible radii and thus a significant range in the possible surface gravity.
Actually, not the telephone sanitizers. We might want to keep those around.
My karma is in a nose dive