US scientists find potentially habitable planet near Earth | Hacker News Reader

US scientists find potentially habitable planet near Earth

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Phil Plait just posted a writeup about this: http://blogs.discovermagazine.com/badastronomy/2010/09/29/po...

His write up is far more suitable for the HN audience, has plenty of science, grains of salt and uses the very scientific word "probably" a lot (that isn't a joke).

His write up is far more suitable for the HN audience, has plenty of science, grains of salt and uses the very scientific word "probably" a lot (that isn't a joke).

I agree. I submitted the link fully expecting that it would simply vote up someone else's submission, but apparently it hadn't been submitted yet. Now it has been: http://news.ycombinator.com/item?id=1742200

Voyager 2 (man's fastest space craft) is traveling 35,000 miles per hour / 60 = 583 miles per second.

187,000 miles per second equals the speed of light.

Light can travel 57,395,520,000,000 miles in one year (roughly 5.7 trillion miles).

So, in 21 years that would equal 57,395,520,000,000 miles x 21 years, or roughly 120 trillion miles.

Thus, if Voyager 2 was our space craft we'd have 583 miles per second x 60 seconds x 60 minutes x 24 hours x 365 days x 21 years to get 386,095,248,000 billion miles towards our new planet.

There is a huge gap between 386 billion and 120 trillion miles, like 311 times.

That means it would take us roughly 310 x 21 years = 6528 years to get there using current technology.

I just don't see us going there as being very practical.

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EDIT: I'm getting down voted for doing the math! Seriously?

If only it were possible to increase the speed of spacecraft somehow.

Wow. I'd never thought I'd see Voyager 2 being cited as the state-of-the-art.

We just need to put our heads together and create a warp drive. Come on people, let's do it. It must be possible! "Warp drive by 2030" - next Obama speech.

"EDIT: I'm getting down voted for doing the math! Seriously?"

"35,000 miles per hour / 60 = 583 miles per second."

I stopped reading right there, please actually do the math if you do the math.

http://www.google.com/search?q=57395520000000%20miles%20per%...

    ((57 395 520 000 000 (miles per year)) * (21 years)) / (35 000 miles per hour) = 3 928 593.15 years

The fastest space craft we have (twin Helios probes) travels at 250 000 km/h

(20 light years) / (250 000 km/h) = 86,340 years

Unfortunately the Helios probes can only get up to that sort of speed because they're going downhill (ie towards the sun). Going uphill to get out of the local gravity well is harder.

At Voyager 2 speeds it takes 340,000 years.

Furtunately, once you leave the sun's gravitational pull (enough), you can accelerate at a constant rate. So "even" if you accelerate at 0.1g, you can reach 0.7c in 100 years.

So if we had such an engine and an energy source, we could get to that planet in 200-300 years.

The cool thing is, technology innovations are accelerating as well, so we will develop better engines faster than the old ones will arrive to the destination. It's a cool race.

You might not need an engine on the craft, just a big reflector and a tightly focused beam on some planetary body that bombarded it with photons.

The problem then would be slowing down at the other end though.

Fire a mirror off ahead of you?

In the book Rocheworld, they do just that. The light sail splits in two, with the outer portion curving to reflect light from the propulsion laser back onto the inner portion to slow down the ship.

> The cool thing is, technology innovations are accelerating as well, so we will develop better engines faster than the old ones will arrive to the destination.

So all we have to do is wait long enough, and at some point we will have already gotten there.

> The cool thing is, technology innovations are accelerating as well, so we will develop better engines faster than the old ones will arrive to the destination.

The plot of Lost In Space (1998) contained that premise.

(As did, to a degree, the conclusion of Ender's Game.)

And Robert A. Heinlein's 1956 http://en.wikipedia.org/wiki/Time_for_the_Stars, one of his "juveniles" that I liked as a teenager.

Theoretically, a nuclear pulse rocket (http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi...) could achieve 0.1c, which would make the trip attainable in 200 years. You would need a lot of nuclear bombs though.

And Project Orion is old nuclear pulse tech. The current state of the art thought on that kind of thing is slighty less crude than dropping fission bombs behind a big shield.

I think that once a habitable planet is 99.9% confirmed instead of 90% confirmed, there will be an unprecedented international cooperation in order to build a probe that can get there at .1-.25c.

It's an interesting time to be a human.

Before I came here, I did my own brief (and likely inaccurate) calculations:

Distance to Gliese 581 g: 21 light years Speed of Helios 2 (fastest manmade object in space) = ~ 241350 km/h Time for Helos 2 to reach Gliese 581g ~= 93 907 years

I couldn't help but think of Carl Sagan's "Pale Blue Dot". 93 thousand years is an awful long time. I'm glad I'm wrong.

But the Helios probes aren't constantly accelerating.

That was my first thought. Sounds close but is unimaginably far away. I keep flipping back to the difficulties for stone-age man to cross the english channel, and the exponential speed of technological progress, and yet I still can't see it happening for a long, long time. But 100 years ago we couldn't fly the length of a football field, now we do it as a matter of routine.

Thus my mind is a flip-flopping mess of 'can't be done', 'you never know', 'can't be done'... you ge the picture.

Then I start worrying about technological progress being lost through war/politics/religion and having a library of Alexandria moment and having to start all over again.

We just need to wait out a bit for YC to fund Zephram Cochrane's warp drive startup.

I think it's not technologically unimaginable -- we know basically what we'd need in order to get there. With a nuclear pulse design, plus sufficient life extension to make people willing to go on 200-year voyages, no reason why the Gliese 581 system can't be our second home. (Hopefully we'll think of a catchier name by then).

Taking a really long-term view, Gliese 581g has certain advantages over Earth. Its M-class sun will still be burning many many billions of years after our fuel-hungry sun has burned itself out.

English Channel: until about 9000 years ago you could walk across. Stone age people had boats too.No historical analogy can come close to interstellar distances.

Fine ; Atlantic Ocean to stone age man. In hindsight, sure, boat development was coming along and it was only a matter of time. But you take the average stone age man, and tell him that you can sail (or fly) across the ocean one day to another land - that's the sort of leap of faith we require now to believe in interstellar travel. Sure the distances are bigger than any analogy, but distances are just a function of speed. At the moment, it can't be done, so we have to rely on some nebulous concept of 'in the future the technology will be developed'. I want to say 'can't be done' but such challenges continually get overcome by the relentless march of technology. So I have to say 'can't say can't'. Thus it messes with my head.

I'd recommend one of my favorite web sites: http://www.centauri-dreams.org/

It has serious discussions about e.g. http://en.wikipedia.org/wiki/Project_Daedalus

Edit: Recent discussion about Project Icarus from a conference: http://www.centauri-dreams.org/?p=14513

Accounting for time dilation if we can get up to 0.999c(hey i dont know if we can ) it should take less than a year. http://www.1728.com/reltivty.htm

I don't know the exact equation, but accelerating any mass beyond that of a single particle or perhaps molecule to that large a fraction of the speed of light borders on impossible. The energy required to accelerate a mass increases exponentially, so getting any appreciable mass to .999c is pretty much out of the question. Again, no equation (if someone has it I'd love to plug in some numbers) but I'm guessing it would require on the order of the total energy output of the sun to get even a modest spacecraft to that velocity.

"The Physics of Star Trek" by Lawrence Krauss had the equation I believe, but I can't find it!

This is exciting, if not surprising, news. We knew that potentially habitable planets must be out there somewhere, but I'm still very excited that we now know where the first one is.

Expect to hear the name "Gliese 581g" a lot more in the future, because this will be the standard hypothetical nearby life-bearing system people will be talking about for years to come. Habitable and only twenty light years away?

The tidally locked nature of the planet is a bit of a bummer, though. If there were water on the surface, I wonder what would happen to it. Will there be a liquid-water ring, or will the water inevitably wind up getting stuck on the cold side, never to remelt? Perhaps a constant system of glaciers flowing from cold side to hot side, melting, blowing to the cold side and snowing down again?

The way I see it, a tidally locked planet is an easier find, because of the high variance in surface temperatures. Relatively rotating planets will have far narrow variances, making most of them uninhabitable based on temperature.

I'm sorry how does the variance in surface temperature help us find it?(especially with current technology). As I understand it pretty much all the exoplanets so far have been found using Doppler shift. The size of the planet, more precisely the mass, and its distance from the star would influence the magnitude of the shift and hence detectability.

It doesn't help you find it. What it does is widen the acceptance criteria.

Instead of needing to find a rotating planet exactly in the "Goldilocks zone", any planet whose surface is hot on one side but cool on the other, such that the range of temperatures in some part of it lies in the zone, is acceptable, because you can suppose a zone of habitability on the edge of light and shadow.

I'm guessing that's easier because if the planet is a bit too hot on average, you can shift the zone into the shadow; and if it's too cool on average, you can shift the zone into the light. If the planet rotates, you've got a bigger problem, especially if it's too hot, because you need to find / build shade.

I hope we don't hear "Gliese 581g" too much. I think a proper name is in order.

It's pretty unlikely this will remain highly talked about after Kepler releases its findings in a few months. Preliminary results show huge numbers of small earth-like planets. I believe they expect to find dozens or hundreds in the habitable zone. Kepler is really what everybody is waiting for and should completely revolutionize planet-finding.

Actually, the most interesting results won't be here til the second half of 2012, if you take the following [somewhat chauvinistic] criteria into account:

- A really interesting planet orbits a planet similar to the sun.

- The goldilocks zone around a planet similar to the sun puts it in an orbit radius of around 1 year (give or take 20% or so) because orbit period is a function of solar mass and distance.

- It takes three occurances to be sure that a "dip" you see in light emissions is probably a pattern rather than a coincidence. It's like colinear points on a plane: two points always make a line, but for three points to be on a line you're pretty damn lucky.

- Kepler was launched in 2009.

So in the end of 2012 we'll have a list of (hopefully hundreds of) confirmed earth-like planets that orbit sol-like stars with a rotation period around 1 year. That is awesome.

I guess a bigger bummer would be if the planet's core doesn't rotate. Apparently, it's the Earth's rotating molten iron core that generates the magnetic field that protects us from harmful radiation.

My first thought was "use big heat pipes to transfer heat from the hot side to the cool side".

Indeed, anyone living there would not have an energy problem at all.

Or a system of shades orbiting the planet, or stationed between the planet and its sun. But by blocking sunlight the overall temperature of the planet would get colder.

Perhaps it has a large habitable moon that does rotate?

"Time dilation would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. That is, the ship's clock (and according to relativity, any human travelling with it) shows less elapsed time than the clocks of observers on Earth. For sufficiently high speeds the effect is dramatic. For example, one year of travel might correspond to ten years at home. Indeed, a constant 1 g acceleration would permit humans to travel as far as light has been able to travel since the big bang (some 13.7 billion light years) in one human lifetime. The space travellers could return to Earth billions of years in the future. A scenario based on this idea was presented in the novel Planet of the Apes by Pierre Boulle." - http://en.wikipedia.org/wiki/Time_dilation#Time_dilation_and...

"A scenario based on this idea was presented in the novel Planet of the Apes by Pierre Boulle." — also The Forever War by Joe Haldeman: http://en.wikipedia.org/wiki/The_Forever_War

Also, A World Out of Time, by Larry Niven - where a ramjet pilot returns to earth, only to find it ruined and way too hot: http://en.wikipedia.org/wiki/A_World_Out_of_Time

Sweet, it's only 20 light years away. A quick 10 month journey at warp 3.

http://en.wikipedia.org/wiki/Time_dilation

Clearly fleitz is assuming he'll be a passenger.

Talking about warp factors and talking about time dilation don't go well together, unfortunately. The Star Trek universe is, as best I can figure out, nonrelativistic.

This is a bit of hand waving (which is OK because we're talking about imaginary sci-fi constructs) but it was my understanding that since warp drive bends space around you, you're not actually going anywhere near the speed of light, and therefore you experience time similarly relative to people at rest.

I'd have to see that on a Minkowski diagram before I believed it made sense.

Two words- Minkowski Compensators.

Just reverse the phase polarity in the coupler coils.

That's what I assumed too. I wonder how they handle the causality problems with FTL communication?

no need for warp in order to travel 20 light years and take 10 months subjective time.

You just need to travel at 99.91% of the speed of light and you'll get a 1/24 time dilation effect.

There is no time dilation with Alcubierre drives because the ship doesn't move, space around it does.

http://en.wikipedia.org/wiki/Alcubierre_drive

From http://blogs.discovermagazine.com/badastronomy/2010/09/29/po...

"But perhaps the most interesting and exciting aspect of all this is what it implies. The Milky Way galaxy is composed of about 200 billion stars, and is 100,000 light years across. The fact that we found a planet that is even anything like the Earth at all orbiting another star only 20 light years away makes me extremely optimistic that earthlike planets are everywhere in our galaxy. 20 light years is practically in our lap compared to the vast size of our galaxy, so statistically speaking, it seems very likely it’s not unique. I don’t want to extrapolate from a data set of two (us and them), but if this is typical, there could be millions of such planets in the galaxy. Millions."

Does anyone know if the "Message from Earth"[1] sent towards Gliese 581c can conceivably be received at this new planet?

If there is intelligent life in that system capable of detecting and transmitting signals of that form (NOT assuming that by any stretch), a response is due in ~2049.

While we're on that topic, wouldn't such a hypothetical civilization already have discovered other electromagnetic radiation from our system by now? Or does it have to be a focused high-power signal as this one?

[1] http://en.wikipedia.org/wiki/A_Message_From_Earth

I find the idea of inhabiting a planet "tidally locked" to its star fascinating. I'd never heard of such a thing until reading that article.

Sufficiently close-in planets inevitably wind up tidally locked to their stars, like the moon is to Earth. And since we're a lot better at observing close-in planets due to their small orbital periods, a helluva lot of currently known planets are tidally locked.

Yeah me neither. Is there any good sci-fi about the concept? Imagine sending a human there, if you could do it in a human life span, I'm sure you'd find volunteers to do it. But what would be the psychological effect of having to live out your life on the terminator in perpetual twilight? Would they eventually go insane and just run into the starlight and cook themselves?

I think there was such a planet mentioned in one of Asimov's Foundation books. It was a pleasant resort planet, as I recall, with the settlements around the habitable ring having constantly perfect weather.

edit: I looked it up: Radole, in Second Foundation. Asimov coined the term "ribbon world" to describe planets like this where the habitable zone forms a ribbon.

Sounds like ringworld would be a better fit for that scenario - and vice-versa, even.

For quite a while, Mercury was thought to be tidal locked. You'll find lots of old SF with that "fact".

Edit: Until 1965, see http://en.wikipedia.org/wiki/Tidal_locking#Planets

Edit 2: Check Larry Niven's first published short story. http://en.wikipedia.org/wiki/Larry_Niven#Work

IANAP, but it seems pretty unlikely that this would be possible, at least in any way short of living in underground bunkers. I would expect that either the atmosphere would boil off from the hot side (if there wasn't enough gravity to retain it), or the gravity COULD retain it in which case you would get constant world-wide hurricane force winds.

IAAP but I'm not so sure what would happen, it's nonobvious. I did find this short article, based on a more thorough research paper from 1997, suggesting it might be possible though:

http://www.treitel.org/Richard/rass/tidelock01.txt

In short, not only can such a tide-locked planet maintain an atmosphere, but it might even be habitable over much of its surface, with an active water cycle and maybe even a near-breathable surface.

That is really cool. Thank you for the correction, and for the article.

A tidally locked planet with a significant atmosphere would not heat up as much as you might think. The atmosphere would transmit most of that energy around the planet fairly quickly. Consider the Earth has a circumference of 24,859 miles and the jet stream has been measured at around 247 MPH at those speeds air would circle the earth once every 4 days. However, far more important is radent heating increases as the fourth power of temperature which is why the moon never goes over 123°C even after 24/7 sunlight for several days at a time.

Mercury.

Well, sort of. 3/2 tidally locked (switches sides once a year due to elliptical orbit)

This was announced a year or two ago, right - is there anything new there?

EDIT: OK, that was Gliese 581 C. This is the new best hope.

Do you guys think we'll come up with a catchy name for this planet (or future "habitable" planets discovered?) Any idea how that naming process would work?

I can't imagine seeing "Gliese 581g" in headlines for years to come.

Pandora

How about 'Tarsonis'?

Bipolarland would work too. It literally has a split planetary personality.

It's amazing to watch the increasing habitability of newly discovered extra-solar planets. Remember a few years ago when a super jovian was an exciting discovery? Sure it was an easy assumption: planets ought to be common, if our system had 9 (yes back before poor pluto was demoted). The spector of the anthropic principle was always there though. Now, to see the discoveries mount - as fast and earthlike as our instruments are capable? That's exciting. Hell, 20 light-years? That's not so far away from the planned orion interstellar trip.

"The planet is tidally locked to the star, meaning that one side is always facing the star "

How is the gravity about the same as earths if the planet does not spin, or is the planet spinning at the same rate that it is revolving around it's star, like the moon. So I guess gravity does not just come from the centripetal force. Are there any other forces that contribute to planetary gravity? If not the planetary year should be very small.

...rambling

Gravitational force is dependent on mass, not how much an object is spinning.

So centripetal force is independent from planetary gravitational force...

A couple more questions. Would the presence of a magnetic field affect habitability? If so how? How likely is a planet this size to have a magnetic field like Earth's?

Say we did colonize this planet, would be be able to launch crafts into orbit from the surface? It seems like our rockets can barely escape Earth's gravity?

That is great, but have they determined whether or not it has unobtainium deposits yet?

On a serious note, how is it that the planet has 4 times the mass of Earth but the surface gravity is "the same or slightly higher" than Earth's?

> On a serious note, how is it that the planet has 4 times the mass of Earth but the surface gravity is "the same or slightly higher" than Earth's?

It could be bigger than Earth: http://www.wolframalpha.com/input/?i=surface+gravity+of+4+ea...

Time to blow this popsicle stand! So long, suckers!

I wonder if we ll reach it on a speed-o-light craft or teleport to it?

> Gliese 581g, has a mass three to four times that of Earth

> The surface gravity would be about the same or slightly higher than Earth's

I'm confused. Maybe it's way less dense than earth, so on the surface you're far from the center of gravity?

The density is unknown, but we assume it to be rocky because... well, at 2 Earth masses there's not much else it could be made of. It can't be ice because it's too warm, and it can't be gas because gas planets that size won't hold together.

But by my calculations a four Earth-mass planet with the same density as Earth should have gravity of about 1.73g. (using http://www.ericjamesstone.com/weird_stuff/gravitator.htm) Which is not that similar to Earth gravity, but not too far off either, in the scheme of things.

Potentially habitable planets that have less mass than Earth does are inherently more difficult to detect, am I right?

Yep. But we are getting closer.

That's a very cool calculator. I tried to work out the math based on sphere volume: V=4/3 x PI x R^3.

  Earth Mass   Radius   Surface Gravity
    1X         6378km        1.00g
    2X         8035km        1.26g
    3X         9198km        1.45g
    4X        10124km        1.59g
    5X        10906km        1.71g

If it's 2X or 3X, it's just adding 30% to 40% body weight. For 4X or 5X, it's like adding 100lb to an 150lb body. We have plenty of people in the 250lb to 350lb range and they have no problem in mobility. Human body can handle the load. It might still be helpful to have exoskeleton help.

You'd probably still have issues if you tried to live there. Your legs can support twice your body weight if they need to, but can your neck support a double-weight head? Human spines are already pretty under-spec for their task, so people living in 2g gravity would probably suffer from a lot more back problems.

It's a pretty small-beer problem on the scale of colonise-another-star-system problems though.

Not to mention that large humans do take time to become large. A 200 pound man doesn't wake up one day weighing 340 pounds. Yes, a human body can adapt to it, massive health problems notwithstanding, but that doesn't mean you can step off a space craft into that situation. To say nothing of doing so after a multi-generation trip through bone- and muscle-wasting space.

This is old news - James Cameron already made a documentary about this place.

edit: My point here, not well made, was that the potential of a discovery of this magnitude, i.e. a virgin planet capable of sustaining humans etc will eventually be exploited and ruined much the same way we have done to earth. The earth or this new planet is not the problem, but the way we exist on it.

If you were meant to live in perfect harmony with nature, you'd be a tree.

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