[HN Gopher] Mission to reach and operate at the focal region of ... ___________________________________________________________________ Mission to reach and operate at the focal region of the solar gravitational lens Author : WithinReason Score : 199 points Date : 2022-07-28 10:22 UTC (6 hours ago) (HTM) web link (arxiv.org) (TXT) w3m dump (arxiv.org) | garettmd wrote: | Can someone ELI5 for me? | MattPalmer1086 wrote: | Use the sun's gravity as a giant lens (bends light) so you can | see a really long way away. | | But the focal point of this lens is about 500 times the | distance of the earth to the sun, so difficult to get to. | walnutclosefarm wrote: | It's an interesting idea, and why not write a paper about it and | try to get it published? Every academic needs papers with their | name on them, and thinking about this had to be fun, if you don't | have anything useful to do with your time. | | But as an actual scientific investment, in my opinion, it belongs | pretty near the bottom of pile of things we should spend our | astronomy / cosomology / astrophysics budget on. The cost per | unit of new information is just way too large, and the risk of | mission failure too high, to justify making it a priority. | superkuh wrote: | It's not a new idea and there already have been dozens of | papers, and entire books (http://erewhon.superkuh.com/library/S | pace/Spacecraft/Deep%20...), published about using the solar | gravitational focus as a lens and sending a spacecraft there. | In fact NASA was already funding early mission studies like the | Heliopause Electrostatic Rapid Transit System (HERTS) a decade | ago. | | And not only is it good for planetary sciences, it's good for | cosmology too since it enables looking at the truly small scale | structure of the cosmic microwave background. A mission to the | gravitational focal line opposite some star should be one of | the highest priorities. | | http://erewhon.superkuh.com/library/Space/Spacecraft/Diffrac... | | http://erewhon.superkuh.com/library/Space/Spacecraft/Direct%... | | http://erewhon.superkuh.com/library/Space/Spacecraft/Image%2... | | http://erewhon.superkuh.com/library/Space/Spacecraft/Mission... | | http://erewhon.superkuh.com/library/Space/Spacecraft/Photome... | | http://erewhon.superkuh.com/library/Space/Spacecraft/Resolve... | JoeDaDude wrote: | Claudio Maccone's proposal, to put a radio telescope at the | solar focal point for SETI or communications purposes, is | included as a chapter titled "Radio Links enabled by | Gravitational lenses of the Sun and Stars" in the book | Communications with Extraterrestrial Intelligence edited by | Douglas Vakoch [1]. | | [1]. https://www.seti.org/book/communications- | extraterrestrial-in... | bowsamic wrote: | Are you a physicist? This sounds like the opinion of a non- | physicist. In physics we usually work on and publish basically | any idea possible, just so that we have a full picture of what | actually is possible and what the challenges are. Of course | it's better if it's practical but that's not a necessity | pmayrgundter wrote: | "Using a meter-class telescope one can produce images of the | exoplanet with a surface resolution measured in tens of | kilometers and to identify signs of habitability." | | Here's gmaps satellite view at ~10km/px | | EDIT: fixed permalink | https://www.google.com/maps/@41.4220797,-93.7912673,6877284m... | | also: https://imgur.com/a/JwHmaIY | | Wow. | bartread wrote: | That link just opens a standard map of the whole globe in a | flat projection - I think you might need to use the sharing | link generator to share what you intended. | simias wrote: | I think that's what they wanted? Although it's still a | strange way to communicate that given that it'll change | wildly based on screen resolution. A screenshot would | probably be a better idea. | rchard2scout wrote: | I'm not sure if it's possible to easily share the correct | settings in an URL, but: | | In the Layers menu, set it to Satellite, Globe view, and turn | off Labels. Then, zoom until the earth is ca. 1275 pixels | wide | abhaynayar wrote: | I think the link intended to show 10 km/pixel, to give an | idea of what it would look like. It shows a scale of length | 1000 km to me, if it is 10 km/pixel then there should be a | 100 pixels within that length, which seems okay as a sanity | check. But yeah, it depends on the screen resolution as well. | pmayrgundter wrote: | Thanks, fixed! | p1mrx wrote: | When you can resolve territorial borders and labels, that's a | pretty strong sign of intelligent life. | codethief wrote: | I think you might want to switch to satellite view. There are | definitely human-made structures that you can recognize at | 10km/px. | pmayrgundter wrote: | Weird, fix didn't work either :( Just use the imgur :) | phkahler wrote: | Didn't they say the spacecraft will have to move around to get | each pixel? That means the planet would turn between pixels and | you wouldn't get a coherent image. It would also take a very | long time to cover 10's of thousands of pixels. May need to | send many imagers and combine the results... | jackmott wrote: | WithinReason wrote: | I wonder if you could use just 1 spacecraft and actually | exploit the rotation of the planet to "scan" the planet | surface in 1 dimension. The movement of your telescope would | provide the other dimension, so in a slow fly-through you | could get a 2D image of the planet surface. So e.g. imaging a | 12000 km (Earth-size) planet at 10 km/pixel would take 1200 | planet rotations, each providing a row of pixels, taking | about 3 years assuming it's rotating at the speed of Earth. | You would just have to know ahead of time the orientation of | the planet's axis of rotation so you approach the "focal | region" from the right angle. | Brian_K_White wrote: | Before I read this... "focal region" sounds nonsensical to me. | Surely the focal length and direction depends on the thing you | want to look at? The "focal region" would be something like a | sphere starting some distance from the sun and extending out in | all directions to infinity? | WithinReason wrote: | I think that's why it's called a focal _region_ instead of a | focal _point_. | simias wrote: | Given the scales we're talking about I presume that everything | you want to look at is effectively "at infinity", as such I | expect that you consider where two parallel rays would meet due | to solar lensing and that's your focal region. | Orothrim wrote: | I don't believe so, I believe that the size and gravity of the | sun have a gravitational effect on space an result in a | focusing of light at 500+AU distance from the sun. Hence the | focal region is around this sphere and is where you would "sit" | to use the sun as a lens and get information about the universe | on the opposite side of the sun. | | https://en.wikipedia.org/wiki/Solar_gravitational_lens | krisoft wrote: | > Surely the focal length and direction depends on the thing | you want to look at? | | Yes. | | And "aiming" your observatory involves moving it on that | sphere. Given the distances involved that is pretty much either | impossible or time prohibitive. | | The region starts at 548 AU from the Sun. So 548 times the | average Sun-Earth distance. | | In an ideal world you would teleport your camera to this | location instantaneously, take a picture and then teleport to | the next location to look at something else. | | We don't know how to do that. The distances are immense. | | So instead we pick a target, and send out a satellite or | satellites on the opposite vector from it to take a peek. There | is a single point where the target will be in perfect focus, | but in practice (as the paper shows) the target is "in-focus" | enough in a larger region that your satellites can take a | picture while they fly through the region around the ideal | point. | adg001 wrote: | It seems there are a pretty good deal of ideas for ever more | sophisticated imaging technologies. That's nice. However it would | be more reassuring to come up, at the same time (or in due | course), with a similar supply of clever ideas for more | sophisticated rocket engines, or, more likely, with a long series | of fundamental contributions to our understanding of physics and | biology. The ambition of the proposed mission is to reach a focal | region ~548-900 AU away in order to image exoplanets which are | distant up to 100 light years. I am sorry to have to remind us | all about this, but given the extenuating long journey to reach a | region that is not any closer than 548 AU, it would be even more | "painful" to discover even more distant exoplanets which would | remain beyond reach for all practical purposes - As per me | discoveries of such level should remind us to reaffirm our | commitment to take care of the only planet we can live for the | foreseeable future. | [deleted] | cptaj wrote: | Astronomy still provides useful insights regardless of whether | we can reach those places or not. | | That said, we are indeed researching ever more advanced | propulsion technologies! | | We've made great strides in electric propulsion, which is far | more efficient for long voyages than chemical rockets. This | tech is already in wide use today in satellites and probes of | all kinds. | | We're ramping up research in nuclear rocket propulsion again. | There are several branches here: nuclear electric, nuclear | thermal and nuclear pulse. Of these, the last one is the least | developed since it basically means using nuclear explosions to | boost you, but it has the most promise for futuristic spaceship | drives. | | There's also the possibility of using antimater pulse drives | but that's a hairy can of worms. Very hard to produce the fuel | in enough quantities. | lstodd wrote: | 30 years.. I wouldn't be surprised when a bigger and better | telescope launched 10 years later arrives there 15 years before | this crazy contraption. | abecedarius wrote: | On that timescale my bet would be on very large telescopes | built in space nearer us (supplanting the ones built on Earth | and launched then unfolded). This wouldn't perfectly substitute | for a solar gravitational lens scope, but it could do a hell of | a lot. | Cthulhu_ wrote: | Maybe, but only if there's a big leap in propulsion technology, | and as far as I know there's not been anything big in that | regard in the past 50-odd years. Closest thing is probably | reusable rockets to reduce cost. | skykooler wrote: | There's a few things that could be used to complete the | mission significantly faster with basically-current tech | (e.g. NERVA, or Project Orion), but even for deep-space | missions they are unlikely to see use any time soon. | sandworm101 wrote: | A much better idea is the terrascope, using Earth's upper | atmosphere as a refracting lens. This wouldn't require a multi- | decade mission, nor a huge sunshield. | | https://arxiv.org/abs/1908.00490 | [deleted] | TomGullen wrote: | An excellent video on this: | https://www.youtube.com/watch?v=jgOTZe07eHA | | Earths atmosphere and weather affects this sort of telescope | IIRC and will filter out some lightwaves but seems like a much | easier win | jcims wrote: | Couple of examples shot from the ISS - | https://www.youtube.com/watch?v=1t8UNxY2bgQ | someguydave wrote: | the sunshield would not be huge at 900 AU | londons_explore wrote: | The fact that this telescope takes 30+ years to get into position | and take a photo, and that it in its lifespan can only look at a | single planet, is a real disadvantage... | est31 wrote: | You just have to mass produce these things and send them to | interesting targets in parallel. | mabbo wrote: | 2042: Earth receives a message from an alien intelligent species | 32 light years away. | | 2109: Aliens receive a reply, which includes a map of their own | world, including where their largest cities are located. | | I'm just saying, this is totally a possibility! We can creep on | the neighbours! | multiplegeorges wrote: | > Aliens receive a reply, which includes a map of their own | world, including where their largest cities are located. | | I think we'd interpret this as a threat, maybe, like a target | map. They might too. | | Probably best to reply with something more innocuous, like the | Fibonacci sequence. | dylan604 wrote: | yeah, that was my reaction as well. | | "We hear you, and just letting you know, we know where you | live and have started targeting solutions. Just so you know, | we're all armed down here!" | causality0 wrote: | _solar sailing technologies and in-space aggregation of | modularized functional units to form mission capable spacecraft_ | | Am I alone in thinking this is somewhat pointless to discuss | before the prerequisite technology is developed? It's a bit like | "how to keep your sentient sexbot from deciding to murder you". | Like if we could do those things in the first place there would | be a thousand applications with a better return on investment | than this. | krisoft wrote: | > Am I alone in thinking | | Probably not. Most people have trouble thinking long term. | | > this is somewhat pointless to discuss before the prerequisite | technology is developed? | | People wouldn't develop said prerequisite technologies if there | are no applications for it. This paper shows that if we would | have those technologies we could get this neat thing. | | > there would be a thousand applications with a better return | on investment than this. | | Name them. | TremendousJudge wrote: | I'd say it's pretty useful to discuss hypotheticals of all | kinds. In this case, generating ideas for uses of a technology | that is under development might increase interest and therefore | funding, or recruit new people to the cause, and generate new | ideas that may be useful for the active development of the | technology. | croo wrote: | Well, Diffe Whitfield envisioned an internet highway around | 1974 then went on to find out how can we keep secrets when | everyone has a computer in his home. | rendall wrote: | > _somewhat pointless to discuss before the prerequisite | technology is developed_ | | From the article "The study reveals elements of such a | challenging mission, but it is _nevertheless found to be | feasible with technologies that are either extant or in active | development._ " (emph. mine) | | It's pointless to discuss the application of technologies in | active development? | | > _there would be a thousand applications with a better return | on investment than this_ | | You veered into a baffling non-sequitur, there. ROI in a unique | science mission to image an exoplanet 100 l.y. distant to a | resolution of 10s km for potential human habitation? The | successful ROI is incalculable. | nautilius wrote: | Yeah, have you heard of that Patent clerk in Switzerland who | wrote about what changes when we ride on a train close to the | speed of light - even though we're still not capable of | building a train that fast, more than a century after. What a | waste. | sp332 wrote: | This would also work for radio waves, right? We would be able to | listen in on radio broadcasts from a distant planet. | hamter wrote: | For those like me who need some kind of reference for the | distances mentioned (548-900 AU), Voyager 1 is 156.5 AU from | earth today. | scotty79 wrote: | I wonder how much faster we could get there with solar sail and | laser boost from Earth | ben_w wrote: | Without specifying the size of the laser, anything from "even | slower" to "whole trip in just under 16 days". | | https://en.wikipedia.org/wiki/Breakthrough_Starshot | | http://www.wolframalpha.com/input/?i=548%20AU%2F0.2c | lazide wrote: | Hah, the latter number requiring some significant percent | of earths mass being converted to energy or something? | vilhelm_s wrote: | Not really, it's the velocity the "Breakthrough Starshot" | probes would reach. They propose[1] that launching each | probe would take 84 GWh, which is not super much (about | 15 times more than a space shuttle launch), but of course | the Starshot probes would be much lighter than this | proposed telescope so it's not directly comparable. | | [1] https://youtu.be/KIDuXQHt8pk?t=1562 | zardo wrote: | Accelerating a meter class telescope to .2 c is well | beyond our current capabilities, but it's nothing like | _that_ fast. | MattPalmer1086 wrote: | There's a nice article on centauri dreams just published | looking at solar and nuclear options for such a mission. | | https://www.centauri-dreams.org/2022/07/26/getting-there- | qui... | pavel_lishin wrote: | One issue would be slowing down when you get there. | | You'd need to carry a deployable/detachable mirror with you | to reflect the laser back at the craft, but that mirror | itself would also get accelerated further out, which means | having to correct for that, etc., etc. | tokamak-teapot wrote: | With a solar sail you can just start tacking, right? | tgarv wrote: | I think a solar sail mostly works at a broad reach or a | run, so it would be more of a jibe than a tack ;) | sp332 wrote: | For this mission, you don't need to slow down or stop. Just | keep taking image data starting at 548 AU and keep going | until you're at 900 AU. | Cerium wrote: | I thought you have to move laterally to get the pixels? | "The data are acquired pixel-by-pixel while moving an | imaging spacecraft within the image." | scottmsul wrote: | The fastest way there would probably be with a nuclear | propulsion engine, as researched in Project Orion. | | https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls. | .. | dublin wrote: | Yeah, the solar lensing point is WAY the hell out there: since | 1 AU is 8 light-minutes, so the 548 AU minimum works out to 73 | light-hours away. When LIGHT takes half a week to make a one- | way trip, you're in the deep space boondocks, folks. | | I haven't read the paper yet, but this thing would have to have | a fair amount of nuclear power, and comms would be a challenge | as well. As the abstract mentions, though, while the project | has a high degree of difficulty, there appear to be no complete | technology showstoppers to actually doing this, so it's at | least as doable (and considerably cheaper than) a von Braun- | style centrifugal space station in Earth orbit. | | It'll be interesting to see if the idea gets any traction... | quirkot wrote: | For those looking for a live look at Voyager status: | https://voyager.jpl.nasa.gov/mission/status/ | [deleted] | alexpotato wrote: | The solar system explorer view they have on that page is | fantastic! | | I recommend clicking on the "solar system" toggle in the | bottom middle of the view. It gives you a real sense of the | planets, probes, asteroids etc that are flying around our | solar system. | | Also reminds me of looking at air traffic control maps and | what that might look like once intra-solar system space | travel becomes routine. | MichaelMoser123 wrote: | An interview with Dr. Slava Turyshev, who is one of the authors | of the paper. They are talking about the project | | https://www.youtube.com/watch?v=lqzJewjZUkk | [deleted] | femto wrote: | I wonder if a cluster of stars can be treated as a MIMO | scattering channel for more distant unknown objects? If so, it | should be possible to resolve details in the unknown object. I | guess the geometry would have to be such that there is | appreciable signal from each star/scatterer (ie. sort of | colinear), but there would be no requirement to be on a focal | line? | londons_explore wrote: | You should also be able to use the fact that empty space is | (very nearly) black to constrain any optimization algorithm. | pmayrgundter wrote: | Neat idea! | femto wrote: | I guess one problem could be that the scatterers/stars are | luminous, so their own emissions might overpower the | scattered signal? Maybe a cluster of darker objects? Or maybe | luminous objects are okay if the scattered waves are coming | from dark regions surrounding the scatterers and have enough | angular separation that they can be resolved from the | scatterer's own emissions? | pmayrgundter wrote: | hmm.. right.. if the angle of deflection is low and the | star is close enough that its light and deflected light | show up very close together. My intuition is this is not | the case... remember Eddington's test of relativity was for | deflection of starlight around our Sun. We're really close, | yet it was observable with the moon obscuring the main | sunlight. | | the article[1] says "For light grazing the surface of the | sun, the approximate angular deflection is roughly 1.75 | arcseconds." So, what, we take the arcsin of 1.75 | arcseconds to get the apparent divergence ratio, and | multiply that by distance to stars? As long as that value | is larger than the aperture of your camera, then you don't | get competing light? Or maybe you'd need something like the | TESS satellite, where you have a screen specially created | to only allow certain beam transits into your detector. | | I've worked with a nearest 10k stars database | (https://celestiary.github.io/, zoom way out) and the edge | of that is about 2k light years away. So very roughly, | let's say there's 1/8th of those in a certain direction... | so you get.. what? some 2k sample points towards some | distant object? But really most of them wouldn't deflect | that object's light towards Earth, but usually over or | undershoot. | | Don't really know how to put these together quickly, but is | giving me some good food for thought! | | [1]https://en.wikipedia.org/wiki/Eddington_experiment | everyone wrote: | Video about it by launchpad astronomy | https://youtu.be/NQFqDKRAROI | ramraj07 wrote: | There's a ton of astronomy YouTube channels but this is now my | favorite, dethroned pbs space time. The video that converted me | was his supernova explanation https://youtu.be/RZkR9zdUv-E - | for all the content out there no one else has anything this | good about supernovae. | WithinReason wrote: | Starshade deploying: | | https://exoplanets.nasa.gov/resources/1015/flower-power-nasa... | | "The "petals" of the "sunflower" shape of the starshade are | designed to eliminate the diffraction that is the central | feature of an Aragoscope." | | "The starshade is a spacecraft designed by Webster Cash, an | astrophysicist at the University of Colorado at Boulder's | Center for Astrophysics and Space Astronomy. The proposed | spacecraft was designed to work in tandem with space telescopes | like the James Webb Space Telescope, which did not use it, or a | new 4-meter telescope." | | https://en.wikipedia.org/wiki/New_Worlds_Mission | SideburnsOfDoom wrote: | I think I've read about using a swarm of these probes "at the | focal region of the solar gravitational lens" (i.e. in spherical | shell starting 548 AU from the Sun) in A Sci-Fi novel. | | I think this one: | https://www.goodreads.com/book/show/13039884-existence ___________________________________________________________________ (page generated 2022-07-28 17:00 UTC)