Near Earth-sized planet found in habitable zone: Gliese 581C

mithridates · Apr 25, 2007

Another source here claims the gravity to be 1.6 times that of the Earth: http://www.kotv.com/news/national/story/?id=125864 I noticed somewhere else that the team will next start using the MOST space telescope to peer at the star and look for and variations in light as it passes in front of the star. If that works we'll be able to know a lot more about its atmosphere and density. <div class="Discussion_UserSignature"> ----- http://mithridates.blogspot.com </div>

rhm3 · Apr 25, 2007

I'm calculating a rough density estimates based on the 5.1 earth mass and 1.5 earth radius. The formula for density is p=m/v (mass/volume). So first I calculate the volume of Earth, using the formula for spheres: (4/3)Pi*r^3 Earth's radius is 6373km...so multiply that by 1.5 yields about 9560km. (4/3)Pi*9560^3 = 3.66*10^12km. Then to find its mass I simply multipled Earth's mass (5.97*10^24kg) by 5.1 which comes out to 30.45kg*10^24. Incorperating the two values into the aforementioned density formula: 30.45*10^24 / 3.66*10^12km = 8.3cm/g density. That is quite high, even for an estimate. If someone catches a mistake, let me know. Although one could postulate a higher density given its 5.1 Earth masses but only 1.5 Earth radius. 8.3cm/g density doesn't sound like an "ocean-planet"...unless the diameter and mass estimates are way off (which I guess is possible), my bet is that it's rocky.

3488 · Apr 25, 2007

My bet is that it is rocky too. If it is a large terrestrial planet, then perhaps it was once the core of a gas giant. We do not have such large & massive terrestrial planets in our own solar system. Wonder if Spitzer could detect any IR from it? This would at least ascertain if it is tidally locked or has an atmosphere. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

heyscottie · Apr 25, 2007

But remember, the 1.5 radius is MADE UP. The wobble method has NO way to determine planetary size. My bet is that a density was assumed, and a radius was then calculated. Because there was such high uncertainty in this number, they made it be a nice, round number -- 50% bigger than Earth. It is a complete fabrication. ALL that we know is an estimated lower limit on mass and an orbital radius.

heyscottie · Apr 25, 2007

And, although there is no evidence for it, I would suspect that a planet orbitting so close to its star almost HAS to be tidally locked. Caveat: The inner planet in this system may provide enough perturbations to make tidal locking more difficult, or even impossible. I expect people are setting up simulations to test a planetary system like this right now to at least theoretically answer this question.

rhm3 · Apr 25, 2007

Very true. There has to be some constraints though...why would they round to 1.5 instead of say, 5 Earth masses? (which would yield a more Earthlike density)

a_lost_packet_ · Apr 25, 2007

I'd like to make one comment: http://planetquest1.jpl.nasa.gov/atlas/atlas_profile.cfm?Planet=340 Notice the entry by planet "Type." To date, there has only been two other planets that fit that description. One is Earth and the other is more like a "Neptune" and over 9000 light years away. Gliese 581 c is a little over 20 light years. That's pretty darn close in the big scheme of things. It's quite astounding when you think about it. Now, it may not mean much to some. But, for me, to see another entry as "Terrestrial" in our very, very, very tiny little collection of known planets coupled with our very limited amount of experience searching for them... is... it's.. just amazing. This early in the game, we've found a planet that just might, could, maybe be a home for life as we know it. This is like finding your car keys only seconds after you've started looking for them... <div class="Discussion_UserSignature"> I put on my robe and wizard hat... </div>

dragon04 · Apr 25, 2007

This is SWEET. <img src="/images/icons/smile.gif" /> The reality of this is personally larger than I expected it to be. There's a planet not much bigger than Earth orbiting a star in its habitable zone, and it's just down the block from us. How long until it gets a "proper" name? I know there are 150 or so extrasolar planets now catalogued, but no other with such profound implications. <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

3488 · Apr 25, 2007

Very true Dragon04. Whilst I think this planet is totally unlike Earth, the fact that it could be a terrestrial planet orbiting within its parent star's ecosphere, is a huge discovery. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

centsworth_II · Apr 25, 2007

"This is like finding your car keys only seconds after you've started looking for them..." One thing is sure, there are A LOT of keys out there! <div class="Discussion_UserSignature"> </div>

SpeedFreek · Apr 25, 2007

I'm finding myself getting increasingly annoyed at the bad science being spouted on supposedly reputable news programs. I just watched the ITV news and they had a section about this subject. The banner was "WE ARE NOT ALONE", and the bullet points listed behind the presenter said "The planet has 5 times the mass of Earth" but the presenter said "It weighs 5 times as much as the Earth". A particular pet peeve of mine. <img src="/images/icons/rolleyes.gif" /> <div class="Discussion_UserSignature"> _______________________________________________ SpeedFreek </div>

MeteorWayne · Apr 25, 2007

MSNBC is about to do their story. I'll watch and see how bad they slaughter the facts <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

meteo · Apr 25, 2007

This is very interesting. However, there are a number of huge unknowns such as... 1) Is it tidally locked 2) Does it have a thick Venus like atmosphere However, although this is the most earthlike exoplanet to be discovered yet there will certainly be more earthlike planets discovered in the next few years. masses could still result in a fairly thick

MeteorWayne · Apr 25, 2007

MSNBC wasn't too bad. I think. They had Bill Nye, the Science guy on as their expert. He's pretty good, no Mr Wizard, but pretty good <img src="/images/icons/smile.gif" /> The new Carl Sagan???? Better than Beakman <img src="/images/icons/tongue.gif" /> He indicated that in addition to the radial shift, microlensing was involoved in this detection. That's why the "I think" above, since I haven't verified that. No outrageous claims like life on another planet or anything like that. Just indications of the possibilities, and the excitement of the discovery. MW <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

heyscottie · Apr 25, 2007

MeteorWayne: He indicated that in addition to the radial shift, microlensing was involoved in this detection. Me: Really? That's the first I heard of it. If that is the case, then we actually CAN get a little more information than what I had been saying. There may be a little more than speculation going into the 1.5 earth radius estimation...

MeteorWayne · Apr 25, 2007

It was the first I've heard of it too, that's why I'm checking. Although, microlensing is AFAIK based only on mass, so does not explain the derivation of the 1.5 X diamter/radius. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

heyscottie · Apr 25, 2007

At the very least, you would now have a better estimate of mass. Instead of giving a minimum mass threshold, you could give a real prediction. You are probably right about microlensing not giving size information. I was thinking about it in terms of eclipsing the far star, but that's not really the way to think about it at all...

search · Apr 25, 2007

Gliese 581C artist's impression

MeteorWayne · Apr 25, 2007

In the originating paper (Thanx RHM3), to be published in Astronomy and Astrophysics, there's nothing mentioning microlensing at all. My response isn't to you, RHM3, I just wanted to connect to the only factual link in this whole thread until your post. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Apr 25, 2007

another good link a_l_p, thanx! <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

MeteorWayne · Apr 25, 2007

heyscottie, didn't mean to offend you, I found your post of what we really DO know about the system, i.e. facts, most on target. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

search · Apr 25, 2007

Very nice. I prefer your version I must say. <img src="/images/icons/wink.gif" />

serak_the_preparer · Apr 25, 2007

Odds for finding car-keys have just gone up... This early in the game, we've found a planet that just might, could, maybe be a home for life as we know it. This is like finding your car keys only seconds after you've started looking for them... 007: 'I never play the odds...' : ) Bookies slash odds on finding ET (Irish Examiner) 25/04/2007 . . . Dr Xavier Delfosse, a member of the European team from Grenoble University in France, said: â€œOn the treasure map of the universe, one would be tempted to mark this planet with an X.â€ The star is more ancient than the Sun, raising the tantalising possibility that life on the new planet may be older and more advanced than it is on Earth. Scientists at the SETI (Search for Extra-Terrestrial Life) Institute in the US plan to listen for intelligent signals from the star system. â€œThe older the star is, maybe the greater the chance that it has produced something thatâ€™s clever,â€ said SETI spokesman Dr Seth Shostak. For William Hill to pay out on an ET bet, the British Prime Minister has to officially confirm the existence of intelligent extra-terrestrial life within a year of the wager being placed. Mr Sharpe said: â€œWe have come a cropper before when, in the early 60s, we offered 1000/1 about man walking on the moon before 1970 and ended up paying out the equivalent of a million pounds, including Â£10,000 to the first man to place such a bet, David Threlfall.â€ As Dr. Delfosse says, 'On the treasure map of the universe, one would be tempted to mark this planet with an X.'

a_lost_packet_ · Apr 25, 2007

I haven't seen anything regarding microlensing either. Perhaps that was just an added "cool" term in the broadcast or he may have been mistaken? After all, this is pretty recent. Any serious production on it might have been rushed just to get it to market. <div class="Discussion_UserSignature"> I put on my robe and wizard hat... </div>

a_lost_packet_ · Apr 25, 2007

Well, there ya have it. Science can go on all it wants about probabilities and various statistics. But, when the bookies actually lower the odds... I wonder if insurance companies will raise the premiums on alien abduction policies now? <img src="/images/icons/wink.gif" /> This may not be "it." We've got a whole galaxy to dig through. But, it is "it" enough to get me excited and yearning for new technology to explore the possibilities. Perhaps this will be a kick in the pants for the world's space programs in general? After all, people don't find some things about space as addictively interesting as we do. A rock is just a rock to them. But, put a newly discovered planet out there that may have similar conditions as Earth and you inspire a whole new generation of adventurers. <div class="Discussion_UserSignature"> I put on my robe and wizard hat... </div>

Near Earth-sized planet found in habitable zone: Gliese 581C

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