This is how we can get a high-resolution image of an exoplanet:
One of the most exciting aspects of the James Webb Space Telescope (JWST) is its ability to image and gather information about exoplanets. But while JWST will give us tons of information about these celestial bodies, there's something that it can't do: take a high-resolution image of an earth-like exoplanet — specifically, an image where we can clearly see evidence of possible life on another world, such as land masses, clouds, and bodies of water.
Slava Turyshev of the NASA Jet Propulsion Laboratory is working on a solution that would give us a clearer picture of an exoplanet.This method would use a phenomenon called gravitational lensing to capture that kind of an image. Gravitational lensing occurs when the gravity of a massive object, like a galaxy or star, bends the space-time around it. This curvature in space-time acts as a lens, causing the light from objects that are much further away to bend around it and become magnified. When viewed at the right angle and distance, the magnified light will appear as a ring, known as an Einstein ring.
Turyshev's proposed solar gravitational lens would use the sun as that massive object, magnifying the light of a distant exoplanet in order to construct a high-resolution image we otherwise couldn't visualize. We sat down with Turyshev to talk about what it would take to reach this goal and how he hopes to achieve it within just a few decades. Watch our video above to see more.
(Score: 2) by JoeMerchant on Monday October 10 2022, @12:49PM (5 children)
The coolest part of this, to me, would be the agile vehicle capable of maneuvering into positions enabling imaging of the targets. The images are nice too, but the vehicle would have truly exciting alternative applications.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 3, Interesting) by Immerman on Monday October 10 2022, @02:02PM (4 children)
What agile vehicle? They even say in the video that any particular telescope would only ever image one exoplanet. They can just be small enough (1m lens) to make it feasible to send out many of them in different directions.
I'm very excited about potential of gravitational lens telescopes; however, they come with one very serious theoretical limitation which should not be overlooked:
The minimum distance to use our sun as a gravitational lens is 550AU (1AU = the distance from Earth to the sun = ~150 million km, for anyone unfamiliar)
To put that distance in perspective Voyager 1, the furthest and fastest space probe we currently have, has taken 45 years to *almost* reach 158 AU.
That distance also means that retargeting the telescope will be VERY limited. To re-aim at something just one degree away, you need to move your telescope one degree around the sun, which at that distance is about 10AU (roughly the distance to Saturn). And out that far your orbital speed is essentially zero (period =~ 13,000 years), not that you'd even be trying for a circular orbit when your telescope will be dead long before it starts falling back anyway.
He's also talking about using solar sails as the main propulsion to get telescopes out far enough in a reasonable amount of time - and while those work great in the inner solar system, they're already starting to lose power fast by the time you reach Jupiter, and will be completely useless at 500AU, where the sun is little more than a particularly bright star.
(Score: 2) by JoeMerchant on Monday October 10 2022, @02:13PM (3 children)
>What agile vehicle?
O.K. - I was still sleepy when choosing the word "agile" - but: capable certainly qualifies... what vehicles have we actually sent 550AU "out there" yet? If it's a serious program, you might characterize the launch program as "agile" (o.k. still a stretch) in being able to launch a series of vehicles to different destinations.
One ironic part: in order to get a good look at the exoplanet, we'll be sending a probe 550AU in the opposite direction.
As for Voyager, Voyager launched in 1977. Sputnik launched in 1958. I think we can do quite a bit better than Voyager in terms of speed and overall vehicle capabilities just where we stand today, 45 years post Voyager 1 launch.
I suspect (strongly) that these craft will be on solar escape trajectories and unable to slow to anything like station-keeping or orbital speed, sooner or later they'll pass the imaging sweet spot and probably just continue on out into the galaxy. Of course 550AU is 0.0087 light years, or 1/500th the distance to Alpha Centauri, so... if the first imaging mission is in EXACTLY the opposite direction of Alpha Centauri, and the imager only took 20 years to get out to 550AU, then in a mere 10,000 more years, give or take, it could be passing through the nearest solar system...
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by Immerman on Monday October 10 2022, @03:09PM (2 children)
Well, we do have proven solar sails now - I guess that's high tech? It certainly has the potential for delivering a lot of delta-V when traveling many AU directly away from the sun. Though a (as yet unproven) electrostatic solar wind sail would be *much* more powerful since thrust falls off as 1/r instead of 1/r^2, and might be a better choice - though keeping the electron gun running for years might introduce an unwanted failure mode. I suppose ion drives could probably do the job too, though that's much more complicated.
Solar escape velocity does seem inevitable if we're going to get in position within only a few decades - after all the Voyagers have exceeded it and aren't going nearly fast enough for our purposes. However that might not actually be a problem.
An important point to note though is that there is no "sweet spot" for a gravitational lens - unlike a traditional lens that has a specific focal plane, gravitational lenses have a minimum focal distance (550AU for our sun), but no maximum. So long as we remain on the line between the sun and target planet we'll be able to continuously image the planet (and anything beyond it) for as long as we can maintain communications with Earth.
I *think* I also remember hearing that the magnification from a gravitational lens actually increases as your distance from the lens increases. But I can't find any straightforward confirmation of that now that I search, and it's too early to try to process discussions targeted at someone with a stronger background in optics.
(Score: 2) by JoeMerchant on Monday October 10 2022, @07:52PM (1 child)
That would be a cool artifact of the mission: pictures start arriving when the camera reaches 550AU and increase in quality as time goes on.
Another cool aspect would be serial production of the same hardware over and over for different targets.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by Immerman on Tuesday October 11 2022, @02:06AM
Yeah it would.
Unfortunately I suspect I was wrong about that. I still can't find any explicit information about light collection or magnification, but the size of the Einstein ring seems likely to be a decent approximation, and that falls off as sqrt(1/distance to lens)
https://en.wikipedia.org/wiki/Einstein_ring [wikipedia.org]
Yeah, a lot of cheap space telescopes would open doors. You could even set up a sun-orbitting Insanely Large Array, which might not be quite as powerful (math anyone?), but would be far more versatile.
(Score: 2) by c0lo on Monday October 10 2022, @01:53PM (33 children)
vs
In other words, pics or it didn't happen.
Aaand... don't hold your breath, the detector needs to be placed 550AU away (currently Voyager 1 is @158AU and Voyager 2 @131AU).
And you'll need to keep the detector in a pretty precise focus for quite a bit of time, as many images of the planet's Einstein ring need to be deconvoluted into an actual image (using computers on Earth).
And there'll be one detector/exoplanet, you can't afford the fuel (or time) to move the detector so that another star's system is focused (at 550AU, 1 degree of 360 means about 1.53AU).
I'm afraid that, if we seriously want this to happen, we'll need to get rid of large scale use of fossil fuel and autocratic/belligerent regimes first.
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by JoeMerchant on Monday October 10 2022, @02:03PM (2 children)
So, TFS says "just a few decades" - and we have an additional 45 years of space engine development since Voyager was designed. That's over 3x as much time for development, and about 10x as many organizations involved in development during the past decades.
Of course it's not a "hold your breath" timeline, but even a few boomers might get to see the first pictures...
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by c0lo on Monday October 10 2022, @03:28PM (1 child)
Unless, that is, they are hit by then by glaucoma or macular degeneration or the like
Nah, who I'm kidding, not gonna happen in a few decades - the cause is not a question of technology or engineering, it's a question of money and will.
After my mind, outposts on Moon would be money better spent in those following decades, especially if it turns out that one can operate a "rocket fuel refinery" on Moon; the highest mass involved in a launch is fuel/oxidizer if you get them from the shallow grav-well of the Moon to a rendez-vous Earth orbit, you can reach farther faster (with all the Moon is a harsh mistress caveats considered).
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by JoeMerchant on Monday October 10 2022, @07:46PM
>it's a question of money and will
As it always is. The few boomers who want this won't get it because the rest of them want lower taxes, free healthcare but not for anyone else, etc
As for priorities, etc. that's where space exploration has missed the pork train for many decades now. While we pick and choose our space missions to make the most of a shriveled up budget, magic money always appears on demand for air conditioning for the troops in the desert, pandemic relief, etc.
Україна досі не є частиною Росії Слава Україні🌻 https://news.stanford.edu/2023/02/17/will-russia-ukraine-war-end
(Score: 2) by Immerman on Monday October 10 2022, @02:23PM (13 children)
What's unproven? We haven't done it yet, but there aren't any serious engineering challenges involved (compared to what we've already accomplished), and we already use gravitational lensing all the time to get better images of distant galaxies - just not using our own sun as the lens. And getting into position just means providing enough delta-V to reach the desired distance, which should be quite doable.
And angular tolerances should be quite high for the same reason significant retargeting will be all but impossible - you need to move 10AU just to change your aiming direction by 1 degree. You'll probably want thrusters to fine tune the trajectory to compensate for the interstellar wind, but so long as you jettison the sail once it's not doing anything useful the drag should be pretty low. And once well beyond the gas giants the trajectory will become very easy to calculate, almost a straight line, while having 100s of AUs for slight trajectory corrections to accumulate into large positional corrections.
>I'm afraid that, if we seriously want this to happen, we'll need to get rid of large scale use of fossil fuel and autocratic/belligerent regimes first.
Why?
He's talking about a 1m telescope propelled by solar sail. We already have the technology, it's not even very expensive (as space projects go). All we have to do is build it, launch it, and wait a few decades for it to reach position. Granted, it would need to be the biggest solar sail made to date to provide enough thrust, but that shouldn't present any serious challenges.
(Score: 1, Interesting) by Anonymous Coward on Monday October 10 2022, @03:22PM (1 child)
I haven't looked at the proposal in any detail yet, but I'd say a very large problem will be stray light from the Sun washing out any exoplanet signal. It is quite challenging to look for dim signals when you are pointed in the same direction as a contaminating light source. In this case the light source is in the field of view. You can try a coronograph-like approach to block out the Sun, but that doesn't solve your stray light problem (and can potentially make it worse now that you've added some more edges to cause diffraction in your field of view).
(Score: 2) by Immerman on Monday October 10 2022, @03:47PM
Obviously you'll need to obscure the sun and its corona. Optics *really* isn't my field, but I do know there have been proposed Starshields to allow more traditional telescopes to directly image exoplanets - they have more of a flower-like shape, and are positioned tens of kilometers from the telescope, which I think they said counteracts the diffraction issues somehow? Perhaps something similar might help when using our sun as a lens.
And I believe the effective lens diameter increases with distance from the sun, so as the telescope continues to get further away the problem will become less significant.
The biggest issue would seem to be selecting targets. This is going to unavoidably be a fairly expensive endeavor for the immediate future, with an incredibly tight viewing cone, and decades of delay before getting any data back. You kinda want to make sure you'll be looking at something interesting via other methods first.
(Score: 2) by c0lo on Monday October 10 2022, @03:44PM (10 children)
[Citation needed] - will be grateful for one that resulted in a deconvoluted/reconstituted image.
We may never get to the time required to see the detector in position, even if we start now. E.g. because Putin is no longer a rational player (if he ever was), so he may just decide (and succeed) to take the world down only because the world doesn't let him have the Ukraine piece of it.
Wanna bet on 'no mission to use grav lensing will depart from the Earth station in the next 25 years'?
It's not very fast either. At least not at the scales attempted until now and larger scales always offer surprises (the void space is not quite as clean [space.com] as one may think).
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by Immerman on Monday October 10 2022, @04:17PM (9 children)
Seriously? Any time you see a "ring" or "bulge" in a space image, it's because you're looking at things through a gravitational lens (and those are only the most obvious examples). Images are distorted (hence the need for deconvolution), but it's not like they're encrypted, with decent spatial awareness skills you can often manage a pretty good deconvolution by eye.
https://duckduckgo.com/?t=ffab&q=gravitational+lens+images&iax=images&ia=images [duckduckgo.com]
As for debris - we expected Webb to get hit by stuff, just bad luck that the first major impact was so soon. There's two important considerations to keep in mind in that respect:
1) Webb is in the inner solar system, where debris is a LOT denser than most places in the solar system.
2) Webb is specifically orbiting our L2 point, and the neighborhood of the Lagrange points are well known to be exceptionally "dirty", holding a disproportionate amount of debris (The L4 and 5 points are particularly bad, but the others are no slouch). They act as a sort of "funnel" concentrating a disproportionately high number of nearby trajectories to pass near them thanks to the same orbital dynamics that make it possible to keep probes in place relative to Earth.
We also only need to travel about 8x faster than the Voyagers to get into position within 20 years, and we have a pretty good idea of the debris they faced. And the scale isn't changing, only the speed. There's not suddenly more stuff in the way at higher speeds. And solar sails are as fast as you want them to be, you just have to make them bigger. They offer low acceleration, but run continuously for years, rather than running out of propellant in a few minutes like the Voyagers and almost everything else we've ever launched. Like ion drives, only simpler and with even greater endurance. That kind of acceleration adds up fast.
The only unknown is the nature of the environment that far beyond the heliosphere, where objects (technically) orbit the sun, but are also subjected to the interstellar medium rather than the solar wind. But we have no reason to believe there will be any problematic density of debris - such debris should be at its worst in the heliopause, where the solar wind and interstellar medium collide, and the Voyagers haven't had any issue passing through that region.
(Score: 2) by c0lo on Monday October 10 2022, @04:47PM (2 children)
I can't manage, that's why I asked for an already deconvoluted one (CG doesn't count)
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 3, Informative) by StupendousMan on Monday October 10 2022, @07:09PM (1 child)
This link shows a picture of an HST image of the massive galaxy cluster Cl 0024+1624.
https://iopscience.iop.org/article/10.1086/310015/fulltext/fg1.jpg?doi=10.1086/310015 [iop.org]
Note the blue galaxy images in that picture. They are all images of a single blue background galaxy, distorted in different ways by the gravitational influence of the galaxy cluster. In the lower-left portion of the images are un-lensed, reconstructed versions of that galaxy.
More details available in the paper from which the image was taken:
https://iopscience.iop.org/article/10.1086/310015/fulltext/5782.text.html [iop.org]
(Score: 2) by c0lo on Monday October 10 2022, @08:06PM
Thanks, grateful, I wish I could mod.
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by c0lo on Monday October 10 2022, @05:53PM (5 children)
Problems with the large scales [klangable.com]:
Alternatively, you will need some large planet at destination to do a grav braking - good luck finding one in the cold space [harvard.edu] and good luck in having the appropriate position to use it, but this punk doesn't think you will be that lucky
And those are only the immediate issues that popped into my head, I'm sure they be lots of others.
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by Immerman on Monday October 10 2022, @08:36PM (4 children)
Keep in mind we're not talking a huge telescope here - they're talking only a 1m primary, with the entire telescope occupying only a couple cubic meters.
1,2,3) And? You won't be accelerating appreciably half the way there, in fact you'll probably do almost all of your acceleration in the first 5% of your journey. Might even want to eject your sail soon after that to avoid drag from the solar wind and interstellar medium. So what? By that point you'll have been been accelerating for a year or two. Even with low acceleration you're going to be going a LOT faster than accelerating in the 1g range for maybe 5 minutes, which is what basically everything to date has done. There's a half-million minutes in a year, if your sail can manage 0.1% the average acceleration of a rocket, it'll be going at least 100x faster after a year.
Rigidity is also not strictly necessary - one of the lightest ways to support a solar sail is to put small weights around the rim and spin it. You'll get sort of a dome curving away from the sun, reducing thrust a bt, but if it saves you a huge amount of mass, so what? That also provides a huge amount of gyroscopic orientation stability, though admittedly at the price of making adjustments more difficult. Though tiny thrusters on the weights will let you do the job, as would having some way to "reel in" the last little bit of the rim (or openable control flaps) to create a net torque.
Spinning also tends to neutralizes any net torque from uneven degradation, etc. since half a rotation later the torque will be in the opposite direction and cancel itself out. Unless you're rhythmically reshaping the sail at the same frequency as the spin it will just introduce a slight spiral wobble around the primary acceleration axis.
4) We almost certainly won't be doing navigation relative to Earth - the obvious option, since we'd like our final trajectory to be a straight down the line intersecting our sun and the target, would be to use the telescope to look back and keep the sun correctly oriented against the background stars near its disc (presumably obscuring the sun itself with some 99.999% opaque coronagraph so it's edges can be accurately seen).
5) Why would you decelerate? We're not trying to stop anywhere, there is no maximum focal distance for a gravitational lens. The only limiting constraint is our ability to get a signal back to Earth - which could be easily extended by sending a repeater after it (or several).
(Score: 2) by c0lo on Monday October 10 2022, @09:58PM (3 children)
Imprecise at "close range" to the Sun (when most of the acceleration takes place), but perhaps a mixed approach could work.
The issue with spinning sail reorientation becomes a bit harder but is solvable as long as the sail is "under enough tension" from the radiation and/or you have enough fuel to control the weight-rockets and for "trimming those tug lines" while adjusting the sail attitude.
The deployment of a huge spinning sail may be more complicated - tricky to do it while the launch vehicle is in orbit around Earth (not a rigid body, passing into or out of the Earth's shadow is is inviting chaos, heliosynchronous orbit aren't possible because of radiation pressure on the sail, the L-points are dirty), I'm afraid one will need to get a bit further out than Earth to start the sail deployment.
But there's a limit imposed on the intensity of the light that the image sensors are able to capture and then another limit on the optical resolution of the 1m mirror+sensor.
You'd be trying to resolve an Einstein ring against the light of the Sun (get it too close to the Sun image and you'll get noise, get it too far from Sun's image and you'll have too little light and a you'll need a larger scanning area to capture the amount of same information. You'd normally compensate dim lighting by longer exposure times, but you are trying to resolve the features of a planet that likely doesn't show you the same face all the time and moves on its orbit. If the planet has clouds too and the star has flares, there'll be a lot of troubles with the deconvolution.
In addition, you'd be trying to discern the features of an exoplanet orbiting in close quarters to its star (feature size ~ 1000km, orbit size ~1-10AU, observing distance in LY) - the light reflected by the planet will be faint in comparison with the light you are receiving from the star (and pray that the orbital plane of the exoplanet is as orthogonal as possible on the observation line - which is at odds with "pick an exoplanet detected by star occultation").
One on top of the other, you have a limited range on the observation axis where you can hope to get practically something - better stay inside that range enough time to get something and even so the endeavor is far from trivial.
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by Immerman on Tuesday October 11 2022, @01:34AM (2 children)
Figure by the time you've reached 10AU your acceleration has fallen to almost nothing - only 1/100th what it was at 1 AU thanks to the 1/r^2 sunlight intensity. So you're basically getting all your delta-V within the first few AU, and then spending the next 16 years and 500+AU making tiny course corrections to end up in exactly the right place. We'll probably be past the asteroid belt before we really have to do much more than rough in the desired trajectory, at which point the sun is getting pretty small and guidance precision is improving rapidly.
Ran the numbers for a sanity check reference - to reach 550AU in 17 years we need to be going 153km/s. To reach that speed in the first 10 AU (at which point the sun is almost useless) we'd need an average of about 8mm/s^2 of acceleration (in addition to whatever is needed to climb out of the sun's gravity well, which is another 10-30%) Or about 80mm/s^2 to get up to speed within the first 1AU - reality would probably mostly be in that range. (Hey, I don't feel like doing math, and I've only got constant acceleration formulas on my quick reference sheet.)
>The deployment of a huge spinning sail may be more complicated - tricky to do it while the launch vehicle is in orbit around Earth
Maybe. Certainly it would have to start high enough orbit to avoid all the satellites and debris - a solar sail is going to be a pretty big target. Not sure Earth's shadow would really be a big issue though, and it's easy enough to avoid entirely with an inclined orbit, since we won't be spending much time in Earth space (even at 8mm/s^2 it only takes about a week to reach escape velocity from LEO, and we'll be accelerating a LOT faster this close to the sun, even if the complexity of operating a solar sail in planetary orbit orbiting takes a huge chunk away)
>But there's a limit imposed on the intensity of the light that the image sensors are able to capture and then another limit on the optical resolution of the 1m mirror+sensor.
True, but the light is coming from several light years away - a few hundred AU more or less isn't going to make any difference. The question is how much light is focused on you by the the gravitational lens.
I've been able to find fuck-all approachable information on gravitational lens magnification, light collection, etc. but perhaps the size of the Einstein ring is a good approximation? From https://en.wikipedia.org/wiki/Einstein_ring [wikipedia.org]
It looks like when the distance to the target is much greater than the distance to the lens, the diameter of the Einstein ring will scale with sqrt[1/(distance to lens)], so going from 550AU to 1100 AU (another 17 years) will only shrink the ring to 1/sqrt(2) of its maximum size, or by about 30%. Maybe half the maximum total light collected?
Meanwhile, an engine plus enough propellant to slow you down from those ridiculous speeds is going to require either mind-numbing amounts of chemical propellant, or fairly powerful ion drives and a nuclear reactor (an RTG is unlikely to cut it). Either of which will radically increase the cost of the mission. (not to mention the size of the solar sail). It's probably much cheaper to simply send out another telescope every decade or two to replace the one that's getting too far away. Assuming the first one even sees anything worth decades of further study. And especially because you'll have another decade or two of telescope advances to incorporate.
Plus, that way if there's nothing of great interest you can send the next telescope to image some other star system instead.
(Score: 2) by c0lo on Tuesday October 11 2022, @04:22AM (1 child)
Hang on, you know that the solar disk has a non-zero angular diameter and the shrinkage of the ring radius may get the two (Sun disk and Einstein ring) too close to resolve
I'll need to apply myself to some maths to get an estimation on how large the Einstein ring's angular diameter in absolute values can be hoped to be observed. I might get some time this week, but again I might not (too much of my procrastination time on S/N already and the delivery date is closing).
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by Immerman on Tuesday October 11 2022, @02:51PM
The angular size of physical objects shrinks with 1/r, so the ratio of Einstein ring size to sun size will actually *increase* as the sqrt(r)
Of course even as the ratio increases, the absolute size continues to shrink, so there's going to be some point at which our telescope can no longer resolve the details of ring. But I doubt that will be when its angular size has only shrunk 30%.
Hmm - the amount of visible ring area would probably be relevant. I'm not sure *exactly* how, perhaps amount of light collected, and possibly the total amount of "pixels" available from the source object, which I *think* would be analogous to magnification? I believe ~500 AU is the point at which the ring gets bigger than the sun so that it's actually beginning to be visible, so...
angular area of sun = S*1/r^2
angular area of Einstein ring = E*1/r
Visible Einstein ring area = E/r-S/r^2; = 0 @ r = ~500AU --> 500E-S = 0 --> S=500E
VEA = E * (1/r-500/r^2)
Which gives a graph that increases rapidly in a decaying, square-rootish looking curve until about 1000AU, and then begins to fall MUCH slower
That's all back-of-the-napkin calculations in a field I know little about, but looking at the curve I *suspect* the imaging would improve for the first 500-ish AU beyond 550, and then slowly decay until it reached the original levels at a few thousand AU.
(Score: 3, Informative) by takyon on Monday October 10 2022, @02:57PM (2 children)
https://en.wikipedia.org/wiki/Solar_gravitational_lens [wikipedia.org]
The proposed solar sails could get it there in 17 years. I'll believe that after it gets funded and launched.
https://arxiv.org/pdf/2002.11871.pdf [arxiv.org]
Still reading this. It needs to use radioisotope thermoelectric generators, but it can also include a radiation-resistant battery charged by the RTG. It seems they are targeting low costs (smallsat design and low launch costs e.g. ridesharing) and using multiple probes. They would use laser communications to send back around 12.5 bits per second at 500 AU (135 KB/day), but possibly more with a different design. "AI" could be used to observe targets of opportunity. Potentially, these probes could observe more than just a single exoplanet, by using the lensing effect and processing the data locally (they say using an FPGA or GPU) to find something interesting that was enlarged. Gravitational lensing has already been used to find objects that were not known to exist.
Here's something to keep an eye on, which would be much closer to home:
https://www.science.org/content/article/space-telescope-would-turn-earth-giant-magnifying-lens [science.org]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by Immerman on Monday October 10 2022, @03:25PM
Probably don't even need AI to get many targets of opportunity - the image field isn't going to be changing quickly at those distances, and round trip communication delays to 550AU are only about 14 hours. It's really the bit rate that's the limiting factor. Ideally you'd want to send back raw images of the entire highly-lensed region, since there's inevitably going to be plenty of more-distant objects beyond the planet benefiting from the same lens.
Using the Earth's atmosphere as a lens? Now there's an interesting idea...
And here I was all set to rant about how Earth is not a viable gravitational lens since the minimum focal plane distance decreases with mass, and for Earth it's 15,000+ AU away.
(Score: 2) by c0lo on Monday October 10 2022, @03:49PM
That's... interestinger is feasible - if only Muskie decides to stop the light pollution of his satellite constellation.
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 1) by khallow on Monday October 10 2022, @03:55PM (12 children)
One detector per star system. Most systems have multiple exoplanets which we have already detected. Even if there's only one serious target, there's probably thousands of lesser targets that would be worth imagining since you already have the telescope in place.
Because global warming or someone's flag will blur the images? My take is that we'll have fossil fuels for a moderate time, but the autocratic/belligerent regimes will be with us for a long time due to human inclinations. Better have a plan B there.
(Score: 0) by Anonymous Coward on Monday October 10 2022, @03:58PM
What do you mean by plan B? A bunker from which NASA can receive the images of an exoplanet?
(Score: 2) by Immerman on Monday October 10 2022, @04:38PM (10 children)
Thousands? I suppose maybe if you include other, more distant stars that happen to be in the background.
It's unlikely we'll be able to image anything much smaller than a large moon in the system with enough detail to be interesting. We might be able to detect large asteroids as single pixels, but even assuming there's a spectrometer on board (I assume we'd want more information about the planet composition than available from the crude color approximation of a camera) they're unlikely to be especially interesting unless something *very* weird is going on.
Actually, even moons might be a challenge - he mentioned an Earthlike planet being 10 pixels across as an example in the video - if that's actually the scale he's aiming for, rather than just an arbitrary number to explain the concept, then even a large moon would only be a pixel or two across, and asteroids may be hard to pick out from the noise.
(Score: 1) by khallow on Monday October 10 2022, @05:21PM (7 children)
(Score: 2) by Immerman on Monday October 10 2022, @07:21PM (6 children)
I mentioned both. Asteroids might be detectable, but are unlikely to be interesting at only a single pixel.
(Score: 1) by khallow on Monday October 10 2022, @10:06PM (5 children)
(Score: 2) by Immerman on Monday October 10 2022, @11:40PM (3 children)
They can be even bigger in theory, all the way up to binary gas giants. It remains to be seen how rare such massive moons are though.
If our system is at all typical, moons big enough to be round could push the number of objects into the dozens. But most would still be single pixels or small clusters, and be of limited interest beyond cataloging their existence. Though we might find an interesting anomaly or two, or even have to revise our ideas of "typical" moon sizes or moon/planet size ratios.
And yeah, we could probably map the orbits and analyze the surface composition of at least the larger asteroids - I just challenge the idea that they would be *interesting*. Unless, as I said, either they or we are very anomalous. They're rocks - assuming they fall into the same M, S, and C classifications as they do here, and in about the same ratios, (and we have reasons to strongly suspect both will be true) there's not really much of interest to be seen unless there is something very unexpected about their orbits.
Here asteroids are of interest because we've never seen such a thing before. And we can get a closer look at anything unusual we find. And we're looking to have a gold rush to them in the not too distant future. And some of them might eventually destroy all life on Earth if we don't intervene.
Around another star though? They're just more rocks. Rocks that we're unlikely to ever see in any greater detail unless there's something else VERY interesting in the system that makes it worth sending a physical probe at several percent of light speed (and mind-boggling expense).
(Score: 1) by khallow on Tuesday October 11 2022, @01:43AM (2 children)
Those classifications are very particular to the Solar System. We don't have reasons to strongly suspect they'll be the same classifications in other star systems.
(Score: 2) by Immerman on Tuesday October 11 2022, @01:54AM (1 child)
Sure, it's there to look at - so is the gravel stuck in the tread of my shoe. Doesn't make either interesting.
>Those classifications are very particular to the Solar System
Citation?
Every third-gen proto-stellar cloud should have broadly similar ratios of elements, which should stratify and react in broadly similar ways to form broadly similar early clumps of debris during stellar formation - aka asteroids. Planet(oid)s accumulate enough material to start having more intense gravitational stratification, tectonics, and interesting chemistry. Asteroids seem to just be left-over debris - every one we've looked at so far has been roughly similar to the others of its class, at least to to the limits of what can be determined from a few pixels, and that's held true for those few we've looked at closer as well. (I would regard Ceres, 16 Psyche, and the few other huge "asteroids" as more rightly being considered planetoids)
(Score: 1) by khallow on Tuesday October 11 2022, @02:40AM
Only if it has a very similar history, star, neighborhood, and non-stellar mass. Those other star systems won't have that.
Left-over debris from some very interesting past, such as the formation of the Solar System, breakup of a protoplanet, and some of the biggest collisions in the Solar System since. Consider the broadest classification you mentioned: chrondite (C), stony (S), and metallic/iron-nickel (M). The chrondite asteroids are among the oldest objects known in the Solar System. The metallic asteroids could have only formed from a protoplanet object that had an iron-nickel core and thus, melting and differentiation of the asteroid. And the stony asteroids might have come from that same protoplanet, but closer to the surface.
The only part that would be guaranteed to show up in something like the Solar System are the chrondite asteroids. Even those would be differentiated by how close they formed to the star (volatiles would get blasted away by being too close to the star) and subsequent collisions.
(Score: 1) by khallow on Tuesday October 11 2022, @04:26AM
(Score: 2) by c0lo on Monday October 10 2022, @11:06PM (1 child)
4:43 [youtu.be] he talks about 1000x1000 resolution. At 13000km diameter (Earth like), that gets a 13x13 km/pixel.
I'd be pleased with 100x100km/pixel
https://www.youtube.com/watch?v=aoFiw2jMy-0
(Score: 2) by Immerman on Monday October 10 2022, @11:47PM
Nice! I skimmed the video (the new information density was pretty low), and must have skipped past that bit. Thanks!
Yeah, with 13km pixels, or even 100km, things get much more interesting. Even larger moons might reveal enough details to be pretty interesting.
(Score: 2) by bradley13 on Monday October 10 2022, @08:26PM (3 children)
Hugely impractical, and not the best solution. Put a bunch of telescopes into an ordinary orbit around the sun. If they are around 1 AU (the easiest option), they can effectively simulate a telescope with an aperture of 2AU.
Everyone is somebody else's weirdo.
(Score: 2) by Immerman on Monday October 10 2022, @08:50PM
Such a telescope array would certainly be useful, and a lot more versatile, but while the simulated aperture is good for resolving detail it doesn't contribute anything to light collection, which is limited by the total combined area of size of your physical scopes.
I also feel like having your scopes all moving at 30km/s in wildly different directions would complicate things... but it probably just makes the math a little more difficult.
1AU wouldn't actually be the easiest option though, unless you only want three telescopes. Orbital dynamics means there's really only three quasi-stable points sharing Earth's orbit - the L3,4,and 5 points in an equilateral triangle around the sun, and L3 isn't very stable. Anything else will rapidly drift out of alignment.
(Score: 0) by Anonymous Coward on Monday October 10 2022, @08:51PM
You can get away with that in the RF, but you're not going to get there optical or IR wavelengths.
(Score: 2) by takyon on Tuesday October 11 2022, @03:39AM
Like AC said, that only works with radio frequencies.
There are plans to try optical interferometry in space, but it will be at more down to Earth sizes, like tens or hundreds of meters.
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