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Earth-Like Planet That Could Sustain Life Found
astroengine writes "An exoplanet, 20 to 50 percent the mass of Earth, has been discovered 20 light-years away and it appears to have all the ingredients conducive to sustaining life. It has enough gravitational clout to hold onto an atmosphere and it orbits well within the 'Goldilocks Zone' of its parent star. However, it would be a very different place to Earth; it is tidally locked to its star, creating one perpetual day on the world. Interestingly, this may also boost the life-giving qualities of the exoplanet, creating stable temperatures in its atmosphere."
The summary is incorrect. The exoplanet has "a mass three times larger than Earth's", not 20% to 50%
genetically modify humans to live in a wider variety of environments
That would never make it through the intergalactic genetic engineering subcommittee. Their chest-pumping and rhetoric would stop it before it hit the hull floor.
(Posted from the year 2089, see you guys soon! The future is great, but the space-beer is a little watered down.) Yankees win in 66, America is nuked by Eskimos in 70, and 89 is to be the year of the Linux holodeck neural interface.
'We are trying to prove ourselves wrong as quickly as possible, because only in that way can we find progress.' RPF
Also not mentioned is that Gilese 581 is class M red dwarf star with a radiation output very different from that of the Sun. The lack of UV light and greater amount of infrared light may have implications for the ability for life to develop.
The star's small power output is why a planet with an orbital period of only 37 days (Mercury orbits in 88 days, for comparison) can be in the habitable zone.
http://en.wikipedia.org/wiki/Gilese_581
Do what thou wilt shall be the whole of the Law
m = 104,328kg
a = g = 9.80665ms^-2
20ly = 1.89E+17m
Nagasaki A-bomb = 80TJ.
Protoplasm. Quiet Protoplasm. I like quiet protoplasm.
20 light years away gives a search area of about 13,000,000,000,000,000,000,000,000 cubic miles. Unless it is spewing massive amounts of radiation all of the time, things like that in that big of a search space are pretty hard to detect. And while 20 light years might be small by astronomical standards, human beings haven't even been two light *seconds* away from the earth.
The ______ Agenda
Well, gravity is different, but not too much so. Summary says .2-.5g, but TFA says 3.0g. Temperature is unknown, but it's about the same distance from its star as we are (relative to the brightness of the star), so the temperature is probably Earth-like. Now, that could be anywhere from Death Valley to Antarctic temperatures, but it's still within reason. Atmosphere is unknown, and probably will remain that way until we send a probe, or get a much more powerful telescope. Chemical composition is unknown, but it seems to be a rocky planet as opposed to a gassy one, so it's possibly Earthlike in that regard.
Short answer: We don't know. Long answer: We don't know, but I'd sure as hell like to find out.
First, TFS is wrong. This planet is 3 to 5 times the mass of the Earth, not 30%.
The article also won't tell you what is speculation and what they've actually seen. The planet was detected through radial velocity measurement of the star. That pretty much means the only thing that has been measured is the planetary mass times the sine of the inclination of its orbit relative to the sun-Gl581 line. Hence the large uncertainty.
When they talk about atmospheres they are speculating. There is no way to tell if this planet has an atmosphere, although the large mass helps the case. There's no way to tell if the planet is covered in an 100 mile deep ocean or if it is entirely dry other than by speculating based upon the composition of the host star. With no eclipses and a small planet to star distance it's going to be a while before we know for sure about either.
When they are talking about tidal locking they are also speculating. While the planet would almost certainly be tidally locked to the star if it were the only planet in the system, it could exist in an orbital resonance with another planet that throws off the tidal locking, or it could have a large moon in close orbit, which would also do the job.
I also haven't looked to see which version of the habitable zone definition they are using. I would suspect the run-away greenhouse to ice-line version.
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there is probably some sort of maximum initial spin rate, and even given that rate the planet might be guaranteed to be tidally locked at this point.
Glad you answered your own question. We have a good idea of what rotation rates are possible when planets form in a disk, probable rotation rates are basically a function of composition and mass (very small objects such as small moons, asteroids, and fragments are more complicated because their rotation rates are going to be affected by frequent impacts, but even then there's a limit to what gravity can hold together)
Basically, the planet in question--Gilese 581g, is very very very old. It orbits a red dwarf star whose lifetime is in the billions of decades--20-30 billion years likely (too lazy to check for an actual figure, but it's much longer than the 10 billion years for our sun). Based on the current age of the system it (and apparently every other planet in that system, from the bottom of the wiki page on tidal locking) should already be locked.
Though a big fan of sci-fi (I would have to be as someone who studied astronomy), I'm afraid I'm not familiar with this one.
However, the great thing about this planet is that there is almost certainly a "too-hot" part, and a "too-cold" part, for humans, due to the tidal locking that you point out. However, somewhere between there, there must be a "just-right" part. This helps confirm that there is a habitable zone on the star.
The furthest away from Earth a living human has ever been, is just behind the Moon (orbit around the moon), or about 1.3 light seconds. Indeed humans have some small craft flying around much further away in space, but no human on board there. And still a long way to go to reach 20 light years.
Certainly life as we know it has evolved to day-night cycles. Life here would be different. Raccoons (night-animals) would be as confused as deer (day-animals). But there isn't reason to believe they couldn't have evolved differently.
As far as the narrow bands of tropics, this actually helps us determine that there are temperate zones. I posted the following above, but after your post, I just don't want to retype:
"However, the great thing about this planet is that there is almost certainly a "too-hot" part, and a "too-cold" part, for humans, due to the tidal locking that you point out. However, somewhere between there, there must be a "just-right" part. This helps confirm that there is a habitable zone on the star."
The gravitational dynamics are rather well studied, for orbital stability. This is a rather robust part of the study (which, as someone interested in many-body dynamics, a very complex subject, is always surprising to me).
There might be some bizarre weather patterns, but there will be a region of what would be, to us humans, a comfortable region. This strongly suggests a nice region for life as we know it.
Could life exist as-we-do-not-know-it in a different extreme environment? Maybe. But a simpler jump is to life-as-we-do-know-it being elsewhere, since we have evidence such life does exist here, so that is why finding a human-suitable environment is so promising.
The weather might not be fun, that's for sure. But ask people in Alaska and the Mojabe---life exists nonetheless. It might be fun (or not) to be a weatherman there.
I believe they determined it as follows:
The planet is close to its star.
The planet has a fairly well known size.
The gravitational force on the near vs. far side can be calculated based on the planet-star distance and the planet size.
Guessing the planet is mostly rock (a very safe guess based on lots of planetary science information), we can guess how much frictional energy is lost in that differential stretching.
Based on the elements observed in the star, we can estimate the age as billions of years old.
The frictional forces would slow down the planet rotation much faster than billions of years. Thus, by now, it would be tidally locked.
The key is that the planet is closer to its star than the Earth. For example, Mercury (which isn't even as close to the Sun as GJ581g is to its star) is in a 3:2 tidal lock between its orbit and rotation. The full 1:1 lock is expected for closer planets. This is the case for the Earth's Moon, which is why we always see the same side of the Moon. This tidal locking is extremely well established with the Earth's Moon.
I answered this above, but probably after you posted this. Just for completion my answer is as follows. The RV-of-the-star itself data didn't imply the tidal locking, but rather extrapolations based on gravitational interactions, as below:
I believe they determined it as follows:
The planet is close to its star.
The planet has a fairly well known size.
The gravitational force on the near vs. far side can be calculated based on the planet-star distance and the planet size.
Guessing the planet is mostly rock (a very safe guess based on lots of planetary science information), we can guess how much frictional energy is lost in that differential stretching.
Based on the elements observed in the star, we can estimate the age as billions of years old.
The frictional forces would slow down the planet rotation much faster than billions of years (I forget the exact value, but less than 1 billion years; if you really want me to spend a few hours doing the calculation for a better estimate, let me know, but it wouldn't really matter). Thus, by now, it would be tidally locked.
The key is that the planet is closer to its star than the Earth. For example, Mercury (which isn't even as close to the Sun as GJ581g is to its star) is in a 3:2 tidal lock between its orbit and rotation. The full 1:1 lock is expected for closer planets. This is the case for the Earth's Moon, which is why we always see the same side of the Moon. This tidal locking is extremely well established with the Earth's Moon.
Good point!
There is some controversy here. GJ 581 doesn't seem to be to dramatically variable. But others are. The lead of SETI wrote a recent paper claiming M dwarfs are not so active as to prevent life or even advanced life. However, this was in response to papers claiming the opposite. It's uncertain, but it seems GJ 581 is stable enough for long enough periods that life can evolve. Even our Sun isn't super stable, yet life exists. Thus ice ages, the Maunder Minimum and Mini-Ice-Age, and the like.
The spectrum of the star wouldn't necessarily tell us about the composition of planets. Some planet-star spectrum correlations have been seen as far as whether stars have planets, but these have not necessarily been tied to causation, and certainly not to composition of the planets. We would certainly need to calibrate any such tracer first, anyways.
The composition-age relationship for stars that you mention has more to do with the generation of stars. Stars today are made out of the waste products from the exploded material from previous stars. That material is enriched by the nuclear processes from those previous stars, meaning they start with more heavy elements. The current generation includes stars today and those from at least as long ago as 10 billion years. Beyond that you start to get to the beginnings of the universe and earlier generations of stars. So no big changes are really expected here, and the phenomenon you cite isn't currently believed to be planet-related, but rather just evolution-of-the-universe related, a very different topic.
I don't think anything about the spectra of the star could identify water at this level of precision. Planets are a billion times fainter than their stars. The spectra had signal-to-noise ratios of order 300:1, which is impressive enough, but nowhere close to enough to see features of the planet. (If Bill Gates, the man of $60 billion, woke up tomorrow with $60x300 = $18,000 to his name, he might need to be put on suicide watch. That is the level of change we are talking about.)
The lorentz factor is only 1.4 at 0.7c. The relativistic doppler effect would then be:
z= 1.4(1+v/c)-1
= 1.4(1.7)-1
= 1.38
This is enough redshift to push yellow into the near infrared and to make a medium blue into a medium red... One reasonable estimate of the intergalactic energy density is about 1.8 eV per cm^3. Let's assume a vastly oversized vessel with 25m^2 area in the direction of travel. 1 m^3 is 1x10^6 cm^3, so we encounter 1.8x10^6 eV per m^3 swept. With our 25m^2 surface, we sweep 4.5x10^7 eV per meter of travel. At 0.7c, we travel ~ 2.1x10^8 m/s. Neglecting some ramifications of relativity, we arrive at a figure of roughly 9.45x10^15 eV/s (*1.602x10^-19 j/eV), or 1.51x10^-3 watts (that's 0.00151 watts or about 1.5 milliwatts). I generate more heat than that by breathing, and these numbers are based on a velocity far exceeding 0.2c and a spaceship nosecone the size of a small building. Where exactly is the scary radiation coming from?
Matter is another story entirely, as even interstellar gas and dust will generate enormous heat through impact. For very small particles, it is likely that some form of ionizing beam (perhaps in combination with a powerful magnetic field) could be used to sweep out the craft's immediate path. Whether or not this would work for something as large as a micrometeorite (or worse, some big chunk of rock) is questionable. Either way some manner of electromagnetic funnel or wedge becomes necessary if only to avoid debris, and may as well be adapted to collect reaction mass.
As for getting up to speed, use your supply of antimatter to catalyze deuterium fusion. Keep your deuterium in the form of hydrocarbons, or perhaps as water ice. If that doesn't do the trick for you then bring along a good supply of transuranics and blast it with antiprotons.
The truly difficult part of such a trip is navigation. Even now, with our best technology put to the task, we still have unexpected collisions with space junk. Finding and avoiding all potentially hazardous masses along the flight path with enough time to avoid collision (and enough power to maneuver) is a staggering task. Even if you have a fuel scoop there is no way your scoop could deflect a marble at those speeds, let alone a rogue planetoid with a very low albedo.
-1 raving lunatic; +6 subGenius... Things even out...