Potentially Habitable Planet Discovered
arbesman.net
arbesman.net
http://www.news.com.au/technology/perpetual-twilight-of-red-...
The link from the main page reads: Odds of life on new planet '100 per cent'
During a press briefing, Prof Steven Vogt told The Daily Telegraph, “Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say, my own personal feeling is that the chances of life on this planet are 100 percent.”
which sounds rather excessive to me.
Will be very interesting to see the results from Kepler in a few years in relation to finding a planet in a similar period at a similar distance to our position in the solar system.
Is this because the Moon is small, and some threshold of gravity is required? Or somehow related to the Moon's cold and inert interior, thus no gaseous volcanoes? Or just a happenstance of composition?
The Moon is a concrete anchor for imagining exosolar worlds.
===================================
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.
In a couple centuries, (hopefully) it'll be a non-issue. Who knows? The important thing is that we actually found something only theory foresee.
Assuming this particular news really did it, because I'm certain I've read similar headlines in the past.
Voyager goes 35,000 miles per hour (given)
... 10 miles per second
Light goes 187,000 miles per second (given)
Voyager goes 1/2000 the speed of light
Light takes 21 years to get there (given)
Voyager takes 42,000 years to get there.
But Voyager was not intended to go fast by interstellar speeds. It just needed to get to all of its planets before its electronics died. Any speed beyond that was a waste and could have been traded off against more data gathering equipment.
When it comes time to send the nanobots with the directions to fabricate exploration gear and giant space arrays to transmit back the results to us, I'm sure we can make them go faster.
One of my favorite sci-fi short story trilogies.
http://www.google.com/#q=21+light+years+%2F+35%2C000+miles+p...
(21 light years) / (35 000 miles per hour) = 402 369.978 years
That ship would get there in 25 years or so, so most of us would live to see the reply on its telemetry around the time our grandchildren are our age.
Then there are the problems of traveling at that speed - which are significant.
"Realistic" designs for interstellar probes generally rely on not carrying the fuel with the probe and having ultralight masses (e.g. Bob Forwards "Starwisp" http://en.wikipedia.org/wiki/Starwisp) - this still requires impressive engineering (a 560km diameter transmitter producing 56GW) for a total probe mass of 1kg and payload of 80g. And that would "only" manage 20% of C.
http://en.wikipedia.org/wiki/Starwisp
Do I believe something like Starwisp will be built - absolutely. In my lifetime? No chance.
I'd be happy if we get people to Mars in my lifetime - something I don't expect to see.
Really, if you want to cross inter-stellar space in any kind of reasonable time - O(human lifetime) - you need to go faster. Possible solutions are: solar sail or new kinds of ion thruster. Both of these impart a very small force (and hence acceleration) for an exceedingly long time, resulting in very high velocities. Your target speed is about 10% of c. In the case of the solar sail it receives momentum from sun for ~ 50% of distance (assuming similar-sized star to our sun), and then is braked by the momentum from the target star for the rest of the journey.
Problem with solar sail is it needs to be GIGANTIC, and composed of materials stronger and lighter than those available today. Additionally force from sunlight is proportional to 1/r^2 so your acceleration decreases with distance.
So, nuclear powered ion thruster is probably the answer. But, obviously, this kind of project is expensive. And either way, you need living quarters for an entire society to live and reproduce.
http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propul...
There's no reason you can't have a multi-generational ship that takes a thousand years to arrive. You don't have to send thousands of people either, it's enough to send a hundred or so, have them populate on the way, and maybe send some frozen sperm & eggs with them to increase genetic diversity.
Another possibility that'll probably become viable within 50-200 years is to not send any humans at all, but to only send a fast & small ship with human sperm & eggs that can start hatching humans once it gets there. Raising the infants could be done with robots and other infrastructure manufactured once we get there.
I could imagine the feasibility of a multi-generational ship lasting 100 - 1000 years, but not longer. Just think of mechanical and materials fatigue. I doubt anything could be built which would last any longer (if that long).
Ideally we'd be trying a mixture of probes and generational ships, while also experimenting with Moon and Mars bases.
If you're able to bring machines that can construct and repair other machines from raw materials the limitation becomes how much material and energy you can bring with you, not the amount of time you're out there.
At that point: why land?
As that's likely something an inventive race will always do, I'll grant matter and energy exhaustion even though it wouldn't be in the form of 'running low on food/fuel'.
But even then, matter and energy are far more safely and easily found, harvested and retrieved if you never enter any planet's gravity well.
If you're thinking more along the lines of a hyper-space scenario, where FTL technology is achieved before self-sufficiency is solved, sure, you'd have more-traditional 'supplies' and need to land and colonize Earth-like planets.
But that was obviously a misreading on my part. Anyway, I completely agree with you that once your ark ship arrives in a new solar system landing on a planet like Gliese 581g would be counterproductive.
Instead of having to deal with a gravity well it would be better to make a home in something like the asteroid belt. You only need energy & resources for manufacturing capacity, a gravity well can only complicate that process.
People might still want to live on planets as a novelty, or for their resources. But I think any society sufficiently advanced to develop a generational ship that can traverse interstellar space would resemble The Culture (i.e. a swarm of migrating ships & habitats) more than they would resemble The Federation (i.e. people mostly living on planets with ships mainly for transport).
Or you can just make people stop dying after this unreasonable short 80 years.
Really, this would be: 35,000 mph / (60 minutes per hour) / (60 seconds per minute) = 9.72 miles per second.
Then just decrease the distance traveled by a factor of 60, so instead of 386 billion miles traveled by V2, it would be about 6.4 billion miles.
http://en.wikipedia.org/wiki/Tests_of_general_relativity#Per...
Following up on some of the references, it does seem like the long-standing belief is that being a certain distance from the parent star strongly predisposes a planet to tidal locking: "planets close enough to their parent star to possess liquid water on their surfaces (the conventional HZ, below) should be tidally locked (Dole, 1964)," (Scalo et al, 2007); "For stellar masses below 0.6 MSun, exoplanets orbiting in the HZ become tidally locked within the first billion years (e.g., Kasting et al., 1993; Grießmeier et al., 2004, 2005)." (Lammer et al, 2007).
EDIT: D'oh! The OP is talking about 581 g, not d. Serves me right to just grab the first article I see on arXiv about a planet in the Gliese 581 system.
http://en.wikipedia.org/wiki/Tidal_locking
which gives a timescale for how long it takes for a body to become tidally locked to the body it orbits. I haven't plugged in the numbers for this planet, but I'm gonna assume it winds up being much shorter than the age of the star.
"Gliese 581 g may be tidally locked to its parent star Gliese 581"
So it's not known for certain.
First order of business for any life that might arise there is to NOT catch the wind and NOT get in the flow.
On the other hand, if there's both sufficient water AND enough air for life as we know it on our planet's surface (excluding the extremeophiles like the flora living in Grand Prismatic Spring for the moment), the terminator wouldn't be nearly as clear as it is on Mercury, which has no atmosphere. Oceans of air and water would help to distribute heat throughout the world, much like they do here on Earth.
Here on Earth, life gets its energy from soaking up solar energy, or from eating things that have been soaking up solar energy, or from eating things which have eaten things which.... you get the idea. The sole exception is at deep-sea geothermal vents, where you can pick up energy from the thermal gradient. On Gliese 581g, there's huge amounts of energy to be picked up just from the constant flow of energy from hot side to cold side, so I'd expect lifeforms to somehow be tapping into that.
Given an earth-like atmosphere, the wind at the terminator would be a fairly constant 20mph from the sunward side to the shadowed side. Elsewhere, it would be slower. The upper atmosphere would circulate much faster than the rotational period of the planet, spreading the heat out pretty evenly over the planet.
Given an earth atmosphere, and the same heat from the sun as the earth, it would be about 25F on the shadow side pole, and 135F on the light side pole.
Of course, tectonics on a tidally locked planet are another thing, and if its surface has fused its atmosphere is probably chock full of H2SO4.
This is the first time I've seen a story about an actual earth-like (with fairly loose parameters) planet that is roughly in the life-zone! Usually headlines that say "earth-like planet discovered!" involve either a frozen rock orbiting way outside of its sun, or a burning pebble right next to it.
However important this particular planet is, I think it's a first as far as fairly plausible life candidates go. Here's to more!
Hundreds of planets like Gliese 581g will probably be found in the next three years. As we slowly build more and bigger telescopes, we'll gain more and more information about them. This is a process that takes decades.
So don't expect "something to happen" tomorrow because of this discovery. Something should happen in your mind immediately, but the real and physical repercussions of this discovery are slow and expensive.
If you want them to speed up, you should lobby your government to increase their funding, or perhaps donate to some of these projects yourself :)
You can expect to hear this story once more: the first time we discover a planet in the habitable zone which isn't probably tidally locked. In another ten years we'll probably know dozens of habitable-zone planets and nobody will care about 'em much.
Still, what are you expecting to happen? With current technology all we can do is sit here and watch the star wobble. We can't get a direct image of the planet, we can't determine its radius, we can't determine its composition, or whether it has an atmosphere, and we certainly can't get there.
Actually the first time a transiting potentially habitable planet (ie one whose orbit takes it across the face of its star as seen from Earth) we will be able to determine its radius and perhaps within our lifetime its atmospheric composition (current instruments are almost but not quite good enough to get a proper absorption spectrum of a transiting exoplanet). So that's something to look forward to.
http://blogs.discovermagazine.com/badastronomy/2010/09/28/th...