I knew I shouldn’t post before my morning coffee. It’s 230 kilometers, not meters.
joema’s math looks right. I assumed a larger distance to the exoplanet and higher resolution requirement.
I was thinking of the Trappist system, 30 light years away, that we know has multiple planets in the habitable zone. I’d really like a better look at that system.
It wouldn’t even cost that much money in the grand scheme of things; I [POST=“18517898”]worked on a study for an interplanetary telemetry, communications, and positioning system[/POST] and even assuming the need for onboard nuclear reactors the costs were somewhere in the US$6B to US$10B range, and would likely be cheaper today by using deployable solar collectors and solar electric propulsion for station-keeping to keep the mass down to something that could be launched by a Delta IV-H or Falcon Heavy. Given that it is a capability that would be required for any more extensive deep space/outer planet exploration or crewed interplanetary missions, it should be a priority, but somehow nothing like this ever makes the cut on the NAS Decadal Survey. (How SpaceX or anyone else is going to be able to “colonize” Mars without such a capability remains to be explained.)
Although nuclear thermal or some other nuclear fission powered system (like fission fragment, nuclear pulse propulsion, et cetera) is often considered necessary for flexible outer planet exploration, it isn’t really necessary provided that you are willing to accept a slow traverse to some arbitrary point using the low energy trajectories through gravitationally neutral points and using momentum assists, i.e. the so-called Interplanetary Transport Network. Of course, the time required to get beyond the orbit of Saturn is probably longer than most careers in planetary science, so it is a hard sell to get someone to push for a mission that won’t even get on-station until they are well into retirement if not dead, and of course, we’d like to see a scientific data return in a reasonable timespan rather than half a century from now, which is always the problem with planetary science (and the space observatories and experiments that often take a couple of decades from conception to even being approved, and even longer to be launched and operational). But it is technically feasible today to create interferometer networks to surveil exoplanets with much greater resolution than are currently available.
Stranger
Although the TRAPPIST-1 system does have at least three roughly Earth-size planets that are in a range where the heat of the star could allow liquid water to exist on the surface, it is a very small red dwarf star (spectral type M8 under the MK classification) with very close orbits meaning that the planets are almost certainly tidally locked, which would have one side very hot and the other frigid. It is unlikely that they have much liquid surface water since it would boil on the bright side and freeze on the far side, although there may be liquid subsurface oceans below a frozen crust or pockets of transitionally liquid water at the boundary depending on tidal forces and rocking. And although 2MASS J23062928-0502285 appears to be quiet now, such stars tend to be variable in output and will periodically flare energetically, dumping out charged particles and intense X-rays that would sterilize any unexposed organic life comparable to anything we know. TRAPPIST-1 is very interesting from a planetological sense because of how well we can observe it (thanks to the edge-on view) and the collection of worlds in tighter orbits than previously thought likely, but it is pretty unsuited to actually hosting any life as we would recognize it, at least on the surface of any of its planets.
Stranger
Keep in mind though, if we had some orbital manufacturing infrastructure and either enough launch capacity for the raw materials or the ability to extract raw materials from asteroids and/or the moon, building a telescope with a lens 10km in diameter wouldn’t be all that hard. You’re in space – you can build the thing out of sheet metal coated in reflective paint, held in place by steel pipes, and it wouldn’t fall apart under its own weight because it doesn’t really have any. As long as you make sure to move it around slowly – and you’re probably pushing the thing with highly efficient but weak thrusting ion engines, so that’s not really a concern – you can go as big as you’d like with the lens.
One of the fascinating things about Earth is that a long time ago I remember the assumption being that since our Sun is ordinary, and our galaxy is ordinary, we must be ordinary in all ways and thus there must be a lot of solar systems with Earthlike planets. But it turns out so many things have to go right to make the Earth the Earth that we might be very special indeed. Maybe even unique for hundreds, maybe thousands or even millions, of light years.
We don’t really know how many earth-like planets there are quite yet. So far we’ve really been detecting mainly gas giants and the like because they are easiest to detect. As our technology improves, we will probably find many earth-like planets.
And then comes the next big question: if it’s possible for life to form on a planet, is it a sure thing? I would think that any planet capable of supporting life will, simply because even if it doesn’t arise spontaneously on the planet, the planet will surely get “infected” at some point.
Life seems to have arisen here on Earth pretty much as soon as conditions allowed. However, intelligent life formed 3.5 billion years later. Also – we have evidence that life arose more than once here on Earth alone. So I’d guess that anywhere complex molecules and an energy source coexist, life arises. I wouldn’t be surprised to learn that our solar system is teeming with simple life, with the gas giants and their moons being the best candidates.
We do know that no civilization too much more advanced than ours has ever devloped in our neighborhood, though, because we are just about getting to the point where we’d be able to spot ourselves. And a civilization more advanced than ours would leave a clearer footprint.
Of course, the universe is still pretty young – or rather, still early in its lifecycle. Most of what came before life began on Earth was pretty inhospitable. If abiogenesis (The beginning of life from nonliving material) occurred multiple times just as soon as conditions were right, it’s pretty likely that the average time it takes for life to form is short. But intelligent life only developed once. Maybe that’s because Earth was unlucky, and most planets do it in 500 million years. Or maybe Earth is unusually lucky, and other planets won’t go from microbe to man for another eight billion years. We won’t really know until we get bettger information about other planets.
Cite?
A km-scale monolithic mirror would never be made, and I doubt that’s possible. The entire surface area must be fabricated and maintained to within less than one wavelength of light.
Even segmented-mirror designs like Web Space Telescope have limits. The largest seriously proposed for terrestrial use was 100 meters. A space telescope that size using a segmented mirror would be vastly more expensive, even if it were possible.
By contrast, a free-flying space interferometer uses a fairly tight constellation of small mirrors in precision formation, acting as one large mirror. That has formidable technical challenges but is probably possible at some scale.
It would be something like this: https://goo.gl/images/CQxZy5
Intelligent life could be extremely rare, but I would think that even confirmation of alien single celled organisms would be the biggest story of all time, much less animal-like creatures.
There isn’t direct evidence per say, because we aren’t talking about the kind of life that fossilized. So perhaps that was a bad choice of words.
Rather, what scientists have found is that if they take a soup of simple organic compounds, of the kinds that form through non-living processes and were common on early Earth, and then subject them to ultraviolet radiation and electricity, they self-organize into all of the basic components of life. They’ve even seen lipids that naturally encircle these molecules forming very primitive cells.
So since it’s so easy to get that close to abiogenesis on such a short time frame, that’s taken as evidence that abiogenesis probably occurred more than once in Earth’s history.
Absolutely-- and single celled life is all that we are likely to find here in the solar system, although there are a few places that could harbor more complex life – the steam vents at the bottom of Europa’s oceans for example.
I was thinking of a segmented mirror – you’re right of course that a constellation of small mirrors would be easier and probably better too, but I don’t think a segmented lens that size is impossible.
Indulge me: I’m not seeing how that is relevant. The telescope lands, waits for the dust to settle - or be blown away by the solar wind - then opens up.
So what? Hubble is in Low-Earth Orbit and thus spends about 50% of its time in the sun.
The solar wind causes the dust, or at least the part on the far side where the solar wind imparts a negative charge. On the day side of the moon the dust is positively charged by the much more powerful direct radiation.
In general one could consider the moon as having a dust atmosphere. It does make me happy the earth has a magnetic field.
Don’t we have enough global warming without a bunch of rockets spewing hot propellant/pollution behind them?
It’s true that a single monolithic mirror, kilometers in diameter, would be pretty poor for imaging, but I could imagine a civilization with a well-developed space infrastructure building one anyway: There are some astronomical applications for which you don’t need particularly good imaging resolution, but where you just want as big a light bucket as you can get.
And there is some evidence that life might have originated multiple times on Earth, but it’s extremely weak and circumstantial. In any event, all of the life that exists now certainly has a common origin, so if there were other origin-of-life events, our kind of life ate them all. You really can’t use the ease of creating prebiotic organic compounds as evidence, because we have no idea how big a step it is from prebiotic organic compounds to life.
Global warming isn’t caused by the temperature of the engines and generators in factories. It’s caused by the buildup of greenhouse gasses in the atmosphere, which allow less heat to boounce off of our surface and back into space – instead, it’s trapped by the gasses.
A rocket like the one described would cause very little pollution, because thrust is generated by pushing an inert gas (inert meaning non-reactive) out the back end. You could push regular air through, if you used a rocketr like that in the atmosphere. But the heat is produced by a nuclear generator – totally clean.
The danger is that the rocket might crash or explode and spew radioactive waste everywhere. So the idea isn’t to use these engines on the surface, but in space, where if they explode or leak they won’t hurt anyone.