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Trio of Super-Earths Discovered
FiReaNGeL writes "A group of astronomers have now discovered a system of three super-Earths around a rather normal star, which is slightly less massive than our Sun, and is located 42 light-years away towards the southern Doradus and Pictor constellations. 'We have made very precise measurements of the velocity of the star HD 40307 over the last five years, which clearly reveal the presence of three planets.' The planets, having 4.2, 6.7, and 9.4 times the mass of the Earth, orbit the star with periods of 4.3, 9.6, and 20.4 days, respectively. 'The perturbations induced by the planets are really tiny — the mass of the smallest planets is one hundred thousand times smaller than that of the star — and only the high sensitivity of HARPS made it possible to detect them' says co-author François Bouchy, from the Institut d'Astrophysique de Paris, France. Clearly these planets are only the tip of the iceberg."
Because our primary method of detecting a planet right now involves looking at its gravitational effect on the star, and planets that have a lot of mass, are near to their star, and go quickly cause the greatest fluctuation in gravitational force.
Short orbital periods are much easier to detect. Most planet hunting activity today is done by watching the parent star for changes in velocity. When a planet is close to the star the changes are both larger and faster, making them much easier to detect.
---they can't be very Earth-like. "Super-Mercury" would be more like it.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
One of the ways we detect planets (not sure about the HARPS) is the measurement of the wiggle the parent star makes. The more massive the planet and/or the faster it orbits, the easier it is to detect the wiggle. Basically, the star will move either side to side or back forth from our vantage point (depending on the orientation of the orbit compared to our position), and this slight movement is used to calculate the mass, speed, etc of the orbiting planets. If the planet is orbiting side to side from our veiw point, we measure the speed the star moves side to side. For back and forth, we measure the slight doppler shift in light as it moves towards and away from us. Since closer planets tend to orbit faster, most of the planets we've discovered so far are large, close, fast-moving ones.
Again, this is only one way this is done, and I'm not sure about this particular planet. I can't make heads or tails of the HARPS link in any case.
Tic-Tac-Toe, Global Thermonuclear War, and relationships all have the same winning move.
> I think it just means its relatively solid, ie: non-gasious, plus they may deem it to be
> in the proper "zone" to become an earth-like planet (not too close, not too far)
With orbital periods of less than three weeks around a sun-like star they are going to be hotter than Mercury: far too hot for life.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
I think your answer is little too glib. If you were standing on such a planet and had no direct way to measure your planet's mass or the local sun's mass, how would you measure the length of a year? Would it be "obvious" that your planet's year was much shorter than an Earth year?
The answer is, you could observe the way the stars change around sunrise and sunset (or some other points in time fixed to the local sun, like solar midnight). The night sky will appear to rotate once over the course of a local solar year, and you would quickly notice that the night sky was changing. With some basic equipment and a watch, you could measure how fast it was rotating and predict the length of the year.
The planets, having 4.2, 6.7, and 9.4 times the mass of the Earth, orbit the star with periods of 4.3, 9.6, and 20.4 days, respectively.
Anything orbiting a star in 4.3 DAYS is extremely close to the star, and could not possibly anything more than a cinder, probably at near rock melting temperatures.
Mercury has an orbital period of 88 days for comparison.
Sig Battery depleted. Reverting to safe mode.
This depends on the star they are orbiting. These orbit a sunlike star, so yes they will be extremely hot.
However planets around very dim red dwarfs can be close and still potentially support life. Location alone won't dictate that however. You also have to have conditions on the ground and ingredients of life in the right amounts and a number of other factors. Bacteria are more likely than complex life because they can survive in a wider variety of environments, or so the thinking goes. However nature has thrown us major surprises in the past. Complex extremophiles (life in extreme conditions) are not out of the question.
"So lacking any evidence that planets are ubiquitous, and even worse that true Earth-like planets exist in the first place even though they can't yet detect them, they are ready to say that they must exist because they have now found some "smaller" hunks of mass orbiting a star?"
No. They say that it's a pretty reasonable conclusion that planets are ubiquitous, based on how ubiquitous they are in the small areas we've studied and given no reason to suppose the small regions we've studied should hold more planets then usual.
"I thought scientific FACT was built on the presence of observed (not potentially observable... OBSERVED) evidence to support the hypotheses and tests devised when using the scientific method. I hope more of this new science, just like the new math, makes into all of those schoolbooks are youngsters are using in school these days."
Oh, you were around before "drawing generalized conclusions from samples when complete data isn't available" was thought up?
As others have mentioned it is a selection bias. Part of this has to do with the detection method. What they do is look at spectral lines from the star to determine how fast it is moving as it 'orbits 'around the center of mass of the star-planet system (this is very close to the center of the star since the star is so massive, so it is more of a wobble than a straight orbit). The closer the planet is to the star, the larger the gravitational force, so the larger the velocity/ doppler shift. So it is easier to find planets with shorter periods. But even if we developed a new technique today that didn't depend on doppler shifts, we would still only find short period planets for the first few years. Why? Because you need to take measurements for at least a full period before you can determine with any accuracy that you're seeing a planet. So planets with 5yr or 10yr periods will not be confirmed right using any new technique, anyways.
And to add to another point made below, it is possible to have a planet with an orbital period measured in days which we could comfortably live on. A white dwarf star would be cold enough to allow for normal temperatures, even at distances closer than Mercury.
I came here for a good argument
These planets are in no way Earth-like, the 'super Earth' designation is just one of planet size. They are rather small in comparison to other extra-solar planets we have discovered.
We only know of these planets from watching oscillations of the star they are around, so there is no way to determine any sort of chemical makeup of the planet. That said, at 20days for an orbit, those planets are baked dry.
Actually we can get a fairly decent idea of what the planet is composed of. Using a technique known as Absorption spectroscopy (http://en.wikipedia.org/wiki/Absorption_spectroscopy) we can begin to get an idea of what the planet looks like. As the planet heats up, it releases gases and particles into its own (albeit weak) atmosphere. Using absorption spectroscopy we can find out what those gases and particles are, and from that we can infer what the crust is like.Two problems with your suggestion. 1) Baseline is not the limit of any planet searches. 2) Planet searches are done with optical frequencies.
You could put a radio telescope on the moon and do VLBI - but not an optical telescope.
The most difficult part right now of detecting planets using Doppler shift is a fixed frequency standard to compare the stars spectrum against - they are measuring centimeter/second movements of the star. Baseline has nothing to do with the current limits. AFAIK, the only optical interferometer of any note is at Keck - and I don't even know if it has been used yet. See this article: http://optics.org/cws/article/research/33693
Picture a ping-pong ball spinning around a light bulb which is in a shade the size of a football. It orbits the shade once every 5 seconds. You can only see the ping-pong ball when it obscures the light from the shade (oxymoron?), as you're some way away. This means that as long as you look at it for more than 5 seconds, you'll see it twice, and can estimate it'll be there again in another 5 seconds. Testing will confirm this.
/. terminology, but it's easy to follow for anybody.
Now, imagine that there's a tennis ball orbiting the same shade, but it takes 30 minutes for each rotation. Who has 30 minutes to look at a damn lamp shade?! We have other stuff to do, man! So, you don't notice the tennis ball so often, despite being bigger.
That's why we may not see many planets with longer orbits, despite them maybe being bigger than ones we do notice.
I know it's not very
Finally had enough. Come see us over at https://soylentnews.org/
I haven't a clue about what level of radiation is still acceptable, except that I guess it's much higher than accepted.. Factors:
- Radiation can vary a lot along location, especially UV, and (primary)alpha and beta radiation is easily shielded. As for gamma, how much gamma radiation is there ten feet under water?
- Planets with tight orbits always have the same side to the sun due to tidal forces. This gives a wide range of temperature and radiation level to choose from.
- Radiation breaks down dna/rna and any kind of cell material. It possible to have cells with huge redundancy and self-repairing capacity to withstand high levels of radiation? 1000 times more than what we have? a million? We're tuned to low radiation levels.
I wonder if red dwarfs are much of a challenge then. In fact, I can take on two of them for breakfast.
I believe it implies the alien is from somewhere other than terra (Earth).
The actual force of gravity at the surface of a planet is not just a function of the mass of the planet. It is also a function of the radius of the planet. So, if a planet had more mass than earth, but also had a radius that was the right size, it could have the exact same surface gravity.
/R^2)
I believe the function is something like:
G * ( [M1 * M2]
Where G is the universal constant of Gravity, M1 is the mass of a test object, M2 is the mass of the planet, and R^2 is the average radius of the planet, squared. Since we have a fraction, if M2 increases, you can keep the fraction constant by also increasing R.
So, to give a bit more concrete example, if the planet has 2 times the mass of Earth, and the radius is Square-root of 2 times the mass of the earth, then the Force of Gravity at the surface is the same.
"Square-root of 2 times the mass of the earth" should read "Square-root of 2 times the radius of the earth".
Also, more generally, if the mass of a planet is X times the mass of the earth, then if the radius is also Sqrt of X times the radius of the earth, the Force of Gravity will be the same.
it is possible to place an observatory on the moon. a few weeks a go new scientist did a story on it:
http://space.newscientist.com/article/dn14066-giant-telescopes-could-be-built-from-moon-dust.html