Hello World
March 13, 2018 4:19 AM   Subscribe

Want to view an alien planet in detail? Simple: create a telescope, send it somewhere between 51 and 185 billion miles away from Earth, turn it around, and use the Sun as a gravity lens to image another world. Focussed through our local star's Einstein Ring, the telescope would bring in enough visual information to resolve features the size of Central Park on an alien surface.

The technology to develop such a telescope - known as FOCAL - is within reach today ([PDF]), although not without some limitations: most significantly, the spacecraft would only ever be able to image a single target, meaning that the planet to be observed would have to be judged very carefully.

(Post is a belated correction to a Mefi comment I left several years ago, being unaware of solar foci at the time).
posted by Bora Horza Gobuchul (42 comments total) 31 users marked this as a favorite
 
What a cool idea, though it'd be a multigenerational effort. An astronomer could have an entire career between launch and the telescope arriving at 500 AU.
posted by ddbeck at 5:16 AM on March 13 [2 favorites]


Main pull quote from the rings article:

But space has proven to be vaster than scientists knew,

This one idea is seemingly missing from most science reporting and too many teaching efforts.
posted by sammyo at 5:28 AM on March 13 [4 favorites]


Pluto is 40 AU, the Voyager spaceship is 125 AU. 500 is a really really long way.
posted by sammyo at 6:07 AM on March 13 [21 favorites]


Thanks for the comments putting things in scale. Somehow I had the impression that the outer planets were further away.

Meanwhile the James Webb Space Telescope is set to launch next year.
posted by exogenous at 6:38 AM on March 13 [2 favorites]


At first I thought "this idea needs more publicity," since it implies that other civilizations might be able to watch us--and so we ought to behave presentably! But then I remembered the large chunk of human nature that would more likely lead to the response of teeth baring and muscle flexing to intimidate any potential aliens. Oh well, either way it might unite us I suppose.
posted by TreeRooster at 7:11 AM on March 13 [1 favorite]


500 is indeed a really long way, but you could get it out there much more quickly than Voyager if that was actually the purpose of the mission. It would still take decades, but not as many as a naive extrapolation.

Seems like an RTG and an ion engine might even give the option of getting something in orbit out there, though some tech development would be necessary to get a power source to last quite that long.
posted by wierdo at 7:11 AM on March 13 [4 favorites]


But space has proven to be vaster than scientists knew,

This one idea is seemingly missing from most science reporting and too many teaching efforts.



I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.
posted by TheWhiteSkull at 7:13 AM on March 13 [48 favorites]


The resulting imagery would be of great scientific value, of course. But would it show any evidence of an alien civilization? It has always seemed to me that the alien civilizations [that are almost certainly] out there, would, after the relatively brief exploratory period of their evolution in which we currently find ourselves, take pains to cloak their planet so as to eradicate all outward signs of their existence. Their calculus (and ours at some point) would be that the odds of evil civilizations in the universe are sufficiently great (or even just non-trivial) that the risk of being spotted and attacked in some way should be avoided at all costs. A defensive stance is far smarter than remaining exposed to dangers of an unknown nature. So not only would identifyable artificial features far smaller than Central Park be avoided, but so would outbound signals, intentional or accidental. (Basically of course this is one of the proposed explanations for the Fermi Paradox, which asks, if alien civilizations are likely to exist, why haven't we heard from them yet?)
posted by beagle at 7:42 AM on March 13 [1 favorite]


it implies that other civilizations might be able to watch us

That was my thought, too. I wonder what configuration of sun size and planet distance would produce a combination of habitable + gravity lens focal point on the planet. (A rather heavy sun, I imagine.)
posted by clawsoon at 7:45 AM on March 13


If any alien society is watching us right now, they are probably seeing us just emerge into the industrial age, or more likely watching a bunch of us bash each others' heads in over a cow pasture in western Anatolia.
posted by TheWhiteSkull at 7:52 AM on March 13 [3 favorites]


Also since space is vast and the Einstein ring needs to be precisely aligned with each star, it would only work for a single target, so we'd want to be really sure we picked an interesting world. Like say if James Webb finds chlorophyll somewhere, that level of interesting. Would hate to send it 2000 AU out (not 500 because as the article states the sun and corona mess the image up) and look at a boring planet...

Oh who am I kidding. There is no such thing as a boring planet. 1 km resultion is better than we have for a lot of solar system planets -- and every world we've ever looked at has been absolutely fascinating. I'm really looking forward to New Horizons flyby of a Kuiper Belt Object end of this year!
posted by puffyn at 7:53 AM on March 13 [4 favorites]


And maybe getting between stars really is hard -- perhaps advanced civilizations simply have thousands of telescopes parked out at the edges of their solar system to keep up with what the neighbors are doing. A 1 m telescope to 2000 AU is a whole different ballgame from an invasion fleet to 200,000 AU, or even to a single robotic probe...
posted by puffyn at 7:57 AM on March 13 [2 favorites]


500 is indeed a really long way, but you could get it out there much more quickly than Voyager if that was actually the purpose of the mission. It would still take decades, but not as many as a naive extrapolation.

The PDF linked from the post talks a bit about this. Even going several times faster than Voyager means waiting 30 or 40 years to reach the 500 AU focus. Or easily more than a century, if you're aiming for the 2000 AU position.

It's a fascinating engineering problem! How do you build something to sit dormant for decades in a hostile environment to then turn on one day and have it work precisely? Also, if anything goes wrong, you don't get to ask questions of anyone who was involved in design and construction, because all of them will be dead.
posted by ddbeck at 8:02 AM on March 13 [3 favorites]


550 AU? Shit, at that point, just go there.
posted by Naberius at 8:21 AM on March 13 [1 favorite]


The closest star is 272,000 AU away.
posted by Hatashran at 8:32 AM on March 13 [14 favorites]


most significantly, the spacecraft would only ever be able to image a single target, meaning that the planet to be observed would have to be judged very carefully.

Is there a limitation here other than the different targets would result moving the telescope 10's or even 100's of AU's? If you're already sending something 50-220 AU out (and it has a nuclear powered Ion drive that can be restarted) then the limitation is time, correct?

And if the telescope is looking at something like the seven known different individual planets orbiting TRAPPIST-1 then the telescope would be moving a lot less to change it's focus, right? At these distances changing your view from TRAPPIST-1 b to TRAPPIST-1 c then that is much more manageable (or at least manageable in a future where we're sending telescopes 200 AU away).
posted by thecjm at 8:37 AM on March 13 [3 favorites]


If we were willing to put fission reactors in orbit we could get there a lot quicker. Very quickly if we wanted to put our otherwise useless weapons of mass destruction towards an otherwise politically (in the sense that the timeline is untenably long) impossible scientific endeavor.

In any event we're talking moon shot money, whether just to get a useful payload that sort of distance that will still work by the time it gets there using existing propulsion systems or to build something that will go fast enough that existing methods of powering spacecraft would be sufficient.

Not that it's even possible currently, even using a scaled up ion drive sufficient for a single shot within the lifespan of the RTGs we'd have to use to power it. All the Plutonium 240 is already allocated and we aren't making any more. Worse, the plans we do have for restarting production involve making only 5ish kilograms a year, which isn't even enough for currently planned demand, much less any new deep space missions.

We've basically let our entire space infrastructure rot in place to the point that things that were once possible no longer are without massive expense.
posted by wierdo at 9:44 AM on March 13 [1 favorite]


The resulting imagery would be of great scientific value, of course. But would it show any evidence of an alien civilization? It has always seemed to me that the alien civilizations [that are almost certainly] out there, would, after the relatively brief exploratory period of their evolution in which we currently find ourselves, take pains to cloak their planet so as to eradicate all outward signs of their existence. Their calculus (and ours at some point) would be that the odds of evil civilizations in the universe are sufficiently great (or even just non-trivial) that the risk of being spotted and attacked in some way should be avoided at all costs. A defensive stance is far smarter than remaining exposed to dangers of an unknown nature. So not only would identifyable artificial features far smaller than Central Park be avoided, but so would outbound signals, intentional or accidental. (Basically of course this is one of the proposed explanations for the Fermi Paradox, which asks, if alien civilizations are likely to exist, why haven't we heard from them yet?)

I think our resident Scottish sci fi writer had a comment here saying the first sign we're likely to have from another civilization would be a rapid warming sensation from the intergalactic equivalent of a bug zapper.

Here it is!
posted by leotrotsky at 9:54 AM on March 13 [3 favorites]


I think our resident Scottish sci fi writer had a comment here saying the first sign we're likely to have from another civilization would be a rapid warming sensation from the intergalactic equivalent of a bug zapper.

The Doctor, in a murmur to a bystander about Prime Minister Harriet Jones: "Don't you think she looks tired?"

Another civilization, as a post-hypnotic suggestion to Rudolf Diesel during one of their regular abduction runs: "I bet you could run this thing cheaper on petroleum than on peanut oil."
posted by flabdablet at 10:40 AM on March 13 [3 favorites]


I have several problems with Fermi. If a star is a million light years away, then the light we see is a million years old. Lots of things can happen in a million years. Even our own galaxy is large enough to fall under this theory. If only in that respect, a commercial from planet X could arrive any day now, or any time in the next 13.4 billion years. Or we may be outside of the so called light cone that allows us to see things far away. In the context of all of time and space, we may be a tad impatient.

We may indeed be alone in the universe if you assume that "we" includes only people who look like Captain Kirk. How about letting the term "we" include intelligent sponges or marine life that simply isn't interested in the sky? It may well be that not all intelligence must share our propensity to acquire, or our determination to dominate. Earthly life does seems to run in that pattern: eat or be eaten. This basic instinct has led to the invention of the chair, a fondness for loud music, and a love of all things pointy.

I hesitate to suggest that Fermi is unimaginative, but in this respect it seems to me that his version of intelligent life resembles humans in rubber suits looking to exploit the new world for lumber, and who have the bad manners to not phone ahead to let us know they are coming.

Anyhow, if they're out there, bring them on. When they get through analyzing our species they won't be able to stop laughing long enough to do us any harm. I say send the sensors out, and hurry up about it.
posted by mule98J at 11:42 AM on March 13


The scale of this is awesome. So much so that given our rate of technological advancement there is the possibility of making the mission obsolete before it is even in position.

Not to say we shouldn’t launch it (we totally should!) but it presents an interesting dilemma. Do we point this at our most promising exoplanet now and risk having better tech to see it later (which makes this mission wasted effort) or save the best planet for another, future mission and spread the observation around more broadly.
posted by m@f at 12:02 PM on March 13


What's with the speculative tone about đź‘˝ life? Didn't the DOD declassify/deswamp-gas chase footage of flying saucers?
posted by Fupped Duck at 12:07 PM on March 13


the first sign we're likely to have from another civilization would be a rapid warming sensation from the intergalactic equivalent of a bug zapper.

To take that a step further, that bug zapper would most likely be wielded by a fully artificial, ie., non-organic, form of intelligence. After it evolved real consciousness out of the rudimentary AI systems built by its planet's inhabitants, it would have gotten rid of them and their inconvenience, post haste. Next, it would look around for external threats and zap anything that appeared to pose a potential threat. In any case, whether the bug zapper's operators are organic or not, the fact we're still here must mean we're still just being monitored, like octopi in a fishtank. But if we talk too loudly about this gravity telescope, all bets are off.
posted by beagle at 12:24 PM on March 13


So, you mean the Borg.
posted by sio42 at 12:36 PM on March 13


I'm not a physicist so I always like to just imagine some things in science and physics are so beyond our understanding that we can't conceive they're possible.

I realize that proper physicists will argue with me about math and laws of nature etc.

But like, what if there was OTHER math. Wouldn't that be so cool.

what if our minds were actually unable to conceive of the math needed for safe fast Star Trek interplanetary travel.
posted by sio42 at 12:42 PM on March 13


Mind-blowing idea. But, light is quantized. Doesn't the resolution of the lens depend on getting enough photons from the exoplanet?

I know, its star sends out lots of photons. But if it's 35 light years away, they're spread out over a sphere of 15,000 square light years. That's a lot of spread. Surely at some distance, it gets to be so spread out that there's not enough photons to make a hi-res image?
posted by zompist at 12:58 PM on March 13 [1 favorite]


What's with the speculative tone about đź‘˝ life? Didn't the DOD declassify/deswamp-gas chase footage of flying saucers?

It was the same level of information we've been constantly getting in the form of those late-night TV shows about what so-and-so pilot Totally Saw and so-and-so heard that so-and-so saw.

It was crap, but the "news" value was how much attention was *still* being paid to it by morons with money and political power.
posted by odinsdream at 1:29 PM on March 13


Wait, this method can realistically only image a 1 km patch of the planet for all that trouble and set of caveats? Kind of a letdown?
posted by polymodus at 2:07 PM on March 13


No, it would image the whole planet with resolution down to the 1km level. Here's a 0.5km res satellite image for comparison.
posted by rhamphorhynchus at 3:01 PM on March 13


I'm trying to imagine the logistics of arrival- you get out to 500 AU and you have to decelerate, right? Seems like that's going to take a lot of fuel. Do you put yourself in orbit around the Sun? Can you just sit there, somewhat stationary in a straight line between the sun and the target, and maintain focus indefinitely?
posted by simra at 4:13 PM on March 13


A 1 meter sensor would be able to image a 1 km patch at a time, but we have panorama stitching now.
posted by ckape at 4:30 PM on March 13 [1 favorite]


Assuming you Hohmann transfer out to 500AU, the most efficient way to do it, and assuming you're using rockets without gravity assists (not something exotic like a light sail or some kind of constant thrust ion drive thing), you'll be in a solar orbit with a 500AU apoapsis and a 1AU periapsis (since you departed from Earth at 1AU). The apoapsis is also the point you'll be moving slowest, so you'll probably just remain close enough to the optimal position for a good while without further adjustment before falling back towards the sun. Circularising your orbit to avoid that would take a bunch more delta-V and a rocket that still works after a decades long transfer out there. You'd still be in an orbit though, there's no way to stop.
posted by rhamphorhynchus at 5:16 PM on March 13


I think this was a confusing sentence in the article? So the mission could only ever see a small fraction of the planet’s surface.

Also the article doesn't say what resolution the 1 m sensor would be able to achieve; only that the Einstein ringed image would have advantages of being 12.5 km wide, and 100,000x brighter than, e.g., the Hubble Space Telescope. But then what does that imply for resolution? Are they saying with a powerful hypothetical sensor you could even see inside Central Park, or is Central Park just a green pixel? And how is that estimated?
posted by polymodus at 5:18 PM on March 13


Also the wiki page seems to suggest:

an analysis of the inherent spherical aberration of the lens will limit the resolution possible

That lens distortion is the only limit on resolution. Super confusing, I don't remember my optics.
posted by polymodus at 5:24 PM on March 13


But like, what if there was OTHER math. Wouldn't that be so cool.

There is endless amounts of OTHER math. That's kind of the point of math. And yes, it absolutely is so cool.
posted by flabdablet at 7:31 PM on March 13 [4 favorites]


m@f: "Not to say we shouldn’t launch it (we totally should!) but it presents an interesting dilemma. Do we point this at our most promising exoplanet now and risk having better tech to see it later (which makes this mission wasted effort) or save the best planet for another, future mission and spread the observation around more broadly."

Well a small lateral push close in would make for a huge displacement at 2000AU. You'd have a lot of ability to change targets for years after launch if you had a constant thrust device. But really if you were going to do this I'd think you'd launch more than one scope. And the scope could probably be used as a regular space telescope during it's journey.

sio42: "So, you mean the Borg."

More like Berserkers.
posted by Mitheral at 8:17 PM on March 13 [1 favorite]


This was also studied as a NIAC proposal, and the Phase I report was recently posted to arXiv here. There's a lot more technical detail for the curious.
posted by Upton O'Good at 11:07 PM on March 13


Surely at some distance, it gets to be so spread out that there's not enough photons to make a hi-res image?

That's the point of using a light-gathering lens that's roughly the size of a planetary orbit.
posted by flabdablet at 2:08 AM on March 14 [1 favorite]


Step 1: Heavy Lift to GEO at economical rates ( See Trucking Industry )

When we got that, I'll continue with the other steps.
posted by mikelieman at 3:01 AM on March 14


Step 1: check out SpaceX rates(1/8 ULA) , consider they really have no competition at the moment but 2-3 smart companies are right on their tail. Extrapolate a few years, Space Trucking!
posted by sammyo at 11:52 AM on March 14


Huh. You inspired me to compare earth-bound and space shipping rates.

SpaceX is advertising $752/lb to low earth orbit. FedEx's absolute most expensive service that I can find (Next Flight, US to Moscow) is $612 for the first pound.

Of course, for FedEx, each additional pound is $15. SpaceX hasn't quite figured that out yet.
posted by miyabo at 7:12 PM on March 14


It may well be that not all intelligence must share our propensity to acquire, or our determination to dominate. Earthly life does seems to run in that pattern: eat or be eaten. This basic instinct has led to the invention of the chair, a fondness for loud music, and a love of all things pointy.

Obviously, our sample size is only one or maybe three if some recent thoughts on early life on Earth turn out to be correct, but natural selection seems to be universal among species on Earth and likely is everywhere. While that doesn't mean any particular alien intelligence will certainly be competitive, it does mean that they likely were at some point in the past and are therefore wired for it, at least until their species is several million years old.

Even the most cooperative organisms we know of essentially wage war on other colonies or other species in their competition for resources even when it isn't strictly necessary for survival. Some symbiotes might not be directly violent toward others, that's only because they outsource.

Many antibacterial agents are themselves tools which bacteria use against other bacteria, though many come from yeasts, fungi, and some plants. It could easily be argued that war is the default state of life. One hopes that intelligence would eventually tame the underlying beast, but given our own track record across many relatively isolated groups is not a good one.
posted by wierdo at 11:30 PM on March 18


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