Earth-Like Planet That Could Sustain Life Found 575
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."
Trivia (Score:2, Informative)
Star Trek fans will know such a planet as "Class M".
The "M" stood for Majel (Roddenberry nee Barrett) who, in Gene Roddenberry's words, "made his life possible".
Summary is wrong. (Score:5, Informative)
The summary is incorrect. The exoplanet has "a mass three times larger than Earth's", not 20% to 50%
Re:Humans are so fragile...if only we were hardier (Score:5, Informative)
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.
Alien astronomers (Score:3, Informative)
Re:Summary is wrong. (Score:5, Informative)
Re:Humans are so fragile...if only we were hardier (Score:1, Informative)
Ethics aside, wouldn't it be easier to genetically modify humans to live in a wider variety of environments?
I think the better option would be to use huge, blue, remote controlled bodies which we can interface directly with our brains.
Re:Venus and Mars (Score:4, Informative)
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 [wikipedia.org]
Re:Time dilation woes. (Score:5, Informative)
m = 104,328kg
a = g = 9.80665ms^-2
20ly = 1.89E+17m
Nagasaki A-bomb = 80TJ.
Re:How can they tell its tidally locked? (Score:3, Informative)
The submitter should have included this bad boy [ucolick.org] (PDF) in his linkage. Expecting to see methodology on a discovery.com website? You'll have an easier time getting Steve Ballmer to cough up the source code for MS Office.
PS: As an EE, you should know the specific type of magic: It's most commonly referred to as FM.
Re:Venus and Mars (Score:3, Informative)
For those specific planets, sure. However, the right combination of atmosphere and gravity would result in a human-habitable planet at those ranges. Habitability isn't just mean solar distance, it's whether or not water can exist in all three common states. If you're so far away (or so close) that the gravity + atmosphere required to see water ice and water vapor would render the planet uninhabitable, then you're outside the zone.
This is of course probably not the official word on the subject, but the 'zone of habitability' covers situations which do not occur in our solar system but would render recognizable life possible.
Re:Only 20 light years??? (Score:4, Informative)
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.
Re:Only 20 light years??? (Score:4, Informative)
Short answer: We don't know. Long answer: We don't know, but I'd sure as hell like to find out.
What this isn't... (Score:5, Informative)
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.
Re:How can they tell its tidally locked? (Score:5, Informative)
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.
Tidally locked means permanent shade (Score:3, Informative)
If the planet is tidally locked, there would be permanent shade on the dark side, and on the shady side of any mountains near the terminator line, which would provide UV shielding of a sort.
And even with no tidally induced tectonics, might there not be some thermally induced tectonics, depending on how hot things get on the sunny side? All that heat has gotta go somewhere, possibly leading to magma convection...
Cheers,
Re:How can they tell its tidally locked? (Score:3, Informative)
It orbits a red dwarf star whose lifetime is in the billions of decades--20-30 billion years likely
The age of the universe is thought to be between 12 and 14 billion years old.
Re:The moon may be relevant (Score:3, Informative)
There are also theories that without the moon, the earth would wobble uncontrollably with no set axis. Imagine the chaos is that turned out to be true ;)
There's also an error in the summary. TFA states the planet actually has 3 earth masses not 20% to 50% of Earth's mass, which makes sense. It's also tide locked like our moon is to Earth.
Re:Venus and Mars (Score:3, Informative)
The habzone is defined as the range at which planetary temperatures could be in the right range for liquid water. Whether temperatures are in that range on a given planet depends on other factors, such as atmospheric density, greenhouse effect, etc. At stellar distances all we can tell (and even that, not easily) is the former -- although we're getting closer to being able to read atmospheric composition under some circumstances.
Swap the orbits of Mars and Venus and they might be darn near habitable. (Mars perhaps not due to atmosphere loss. Venus perhaps not due to a too-thick even if not too-hot atmosphere, unless a lot of it froze out as polar caps.)
Re:I work with 2 of the authors (Score:4, Informative)
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.
Re:Only 20 light years??? (Score:4, Informative)
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.
Re:Life (?) (Score:3, Informative)
I do agree that other forms of life MAY be possible, but having a background in biochemistry you realize just how important water is to any concept of life to arise. Solubility, reactivity, and relative density properties that are necessary for any life to form are pretty much unique to water.
Re:I work with 2 of the authors (Score:5, Informative)
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.
Re:I work with 2 of the authors (Score:5, Informative)
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.
Re:I work with 2 of the authors (Score:4, Informative)
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.
Re:I work with 2 of the authors (Score:5, Informative)
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.)
Re:The chances are pretty much zero (Score:3, Informative)
So, if the plates are locked, atmospheric CO2 quickly passes the tipping point and you end up with Venus - except that if it were the Earth (plus the mass of the moon, plus the other ejecta that were blasted away when the moon was created by the impact), instead of 22 atmospheres, we'd be at 45 atmospheres. In other words, instead of Venus being the hottest planet in the solar system, it would be Earth.
Forget oceans - all the water vapor is tied up in an H2SO4 haze.
Dark side? It would be almost as hot. That dense an atmosphere is very efficient at redistributing heat - plus, light bends almost completely around the planet due to the dense atmosphere. The dark side wouldn't be dark anyway - not with rocks so hot they glow.
When it comes to inhabitable planets, there's no place like home.
Re:Wow (Score:3, Informative)
"The Great Debate" occured in 1920 and it took a while after that to figure out that Heber Curtis was right. It's crazy that it took so long to develop the telescopes needed to find out there are other galaxies out there.
And in less than 90 years since then, we now have the technology to take those Deep Field pictures showing tens of thousands of galaxies at a time when the Universe was 300 million years old.
Re:Only 20 light years??? (Score:3, Informative)
Yes, but the loneliness, distance, and lack of exercise has caused space-madness. He calls himself V'Ger now and has gotten really big.
Re:Time dilation woes. (Score:5, Informative)
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.
Re:The chances are pretty much zero (Score:3, Informative)
Re:Time dilation woes. (Score:2, Informative)
Depends. According to whom is the ship accelerating at 1 g?
According to anybody in any inertial frame. Acceleration is not relative.
Re:Annddd.... (Score:3, Informative)
But realistically, chances aren't ANYWHERE near either number. We simply don't know how likely it is for life to exist on planets with a certain temperature and composition.
We know there's life on earth. That's a single data-point. Any scientist knows that drawing strong conclusions from a single datapoint is nuts.
Sure, if we had investigated 23 earth-similar planets, and found life on every single one of them, then we'd have enough data to say that earth-similar planets tend to have life on them.
But that's not presently the case. He may *believe* we will find it to be the case, in the future. But random hunches, don't typically hit with 99.99999999% probability.
Re:Only 20 light years??? (Score:3, Informative)
From Wikipedia - Red dwarf (Score:1, Informative)
I found this really interesting section on Wikipedia. I thought I'd copy it before some Aspie deleted it because of "no original research" or some crap:
Extrasolar planets were discovered orbiting the red dwarf Gliese 581 in 2005, about the mass of Neptune, or sixteen Earth masses. It orbits just 6 million kilometers (0.04 AU) from its star, and so is estimated to have a surface temperature of 150 C, despite the dimness of the star. In 2006, an even smaller extrasolar planet (only 5.5 times the mass of Earth) was found orbiting the red dwarf OGLE-2005-BLG-390L; it lies 390 million km (2.6 AU) from the star and its surface temperature is 220 C (56 K).
In 2007, a new, potentially habitable extrasolar planet, Gliese 581 c, was found, orbiting Gliese 581. If the minimum mass estimated by its discoverers (a team led by Stephane Udry), namely 5.36 times that of the Earth, is correct, it is the smallest extrasolar planet revolving around a normal star discovered to date and since then Gliese 581 d was discovered which is also potentially habitable. (There are smaller planets known around a neutron star, named PSR B1257+12.) The discoverers estimate its radius to be 1.5 times that of the Earth.
Gliese 581 c and Gliese 581 d are within the habitable zone of Gliese 581, and are the most likely candidates for habitability of any extrasolar planet discovered so far.[8]
An announcement in Physorg September 29, 2010 describes the discovery of a remarkable new planet: Gliese 581 g. [9] It has a near-circular orbit in the middle of the star's habitable zone and liquid water could occur in some regions on its surface. If confirmed, this would be the most Earth-like exoplanet yet discovered, and the first strong case for a potentially habitable one. Gliese 581 g has a mass three to four times that of Earth and an orbit of about 37 days. It is probably a rocky planet with plenty of gravity to retain a more massive atmosphere than Earth. However, as to be expected for a planet in close orbit round a red dwarf, it is tidally locked, with one face perpetually in darkness and cold, probably covered in glaciers of frozen atmosphere. The implications for the possibility of life on the planet are complex and uncertain. The greatest point of uncertainty is not whether an environment as stable and varied as the surface of that planet could sustain life, but whether the radiation supplied by a red dwarf could generate life in the first place.
In the light of recent proposals suggesting that life on earth might have originated near submarine hotspots[10][11], that objection might fall away, and other considerations raise intriguing possibilities on the assumption that life had indeed been established on Gliese 581 g. The fact that the planet is tidally locked, and that the sun is a red dwarf, suggests that the system might well be very old in comparison to Earth, and that physical conditions in its various zones should be enormously stable. There would have been ample opportunity for life forms to have colonised a large range of ecological niches.
Some of those niches could be very rich and accommodating. Given such a relatively high planetary gravitation, the mass of frozen gases and liquids on the night side of the planet should form glaciers all around the twilight limb of the planet. As the material encroached on the warm side, it would variously melt and volatilise, leaving moisture- and mineral-rich moraines in an effectively permanent system supplying energy and material to a potentially vast number of organisms. A sort of Amazon-scale ecology girdling the planet throughout the twilight zone, possibly petering out towards the hotter areas of the periastral face of the planet, or equally possibly, intensifying towards its centre.
All such points are subject to speculation, but the only strong grounds for pessimism arise from the uncertainty of the generation of life on the planet in the first place. Should there indeed be no life on the planet, the glacial behaviour at least, on the assumption that the planetary atmosphere is thick enough to support any, should in any case be intriguing. However, consider some of the points discussed in the section dealing with habitability.
Re:I work with 2 of the authors (Score:3, Informative)
The comparison to Mercury seems to be based on the planet's proximity to its star. The star is much colder that the Sun, so a closer-in planet like Mercury would not be nearly as hot as Mercury finds itself.
In terms of size of the planet, this one is much more like the Earth. Mercury is really very small in comparison, and does not have much gravity to retain any atmosphere even if it were located where Earth is. So here the comparison to Mercury really doesn't work well.
Re:I work with 2 of the authors (Score:3, Informative)
These are actually some rather complex atmospheric questions, but it seems likely that winds on the planet would help mix the temperatures all over, making them more moderate. But it is possible the dark side would have more liquidification and freezing of parts of the atmosphere. On Earth we call this rain and snow...not necessarily bad things.
It would be fascinating to study this planet's weather patterns to compare to the Earth's, from a scientific point of view. But it seems likely, no matter the patterns, that some stable point exists where life could thrive.