Could we turn the sun into a gigantic telescope?

[Admin]

Using a phenomenon known as gravitational lensing, it might be possible to use the sun as a gigantic telescope to peer deep into space.

Could we turn the sun into a gigantic telescope? : Read more

 

[George²]

Yes, we can theoretically use the Sun as a giant telescope. Does it make sense? Firmly no. It would be cheaper, faster, and more operable to build an optical telescope with a primary mirror diameter of a full mile, at a distance of tens of thousands, or even several million kilometers from Earth. Just reaching the focal point of the Sun is unachievable with today's technology within a lifetime and even with those of the next 30-40 years. Moving the telescope's camera to view an object in a sector in a sufficiently different direction from the original may require traveling many hundreds of billions of kilometers more.

 

[nforystek]

I think I've seen this, so be careful you don't poke your eye out. It must hurt with the sun doing the poking. I would call it the ALL camera. Altitude, Longitude Latitude, like it's God mode on cell walls. Anyway, just thinking about it (how it does utilize the sun and would be like more advanced of a satellite form NASA like the Hubble, not so traffic control) all of a sudden, I received case documents with James Webb's name on them. 2017. I have no idea what that was about.

 

[Mr Man]

It seems like using the earth would be a logical stepping stone. Focus is closer and more accessible with today’s technology

 

[Unclear Engineer]

Wouldn't the effective focal length of the Earth be longer, not shorter, than the effective focal length of the Sun? Less mass would bend the light paths less, so the paths would converge more slowly. The difference in diameter is not the most important factor for determining effective focal length.

 

[SpaceCaseAli]

Yes, we can theoretically use the Sun as a giant telescope. Does it make sense? Firmly no. It would be cheaper, faster, and more operable to build an optical telescope with a primary mirror diameter of a full mile, at a distance of tens of thousands, or even several million kilometers from Earth. Just reaching the focal point of the Sun is unachievable with today's technology within a lifetime and even with those of the next 30-40 years. Moving the telescope's camera to view an object in a sector in a sufficiently different direction from the original may require traveling many hundreds of billions of kilometers more.

I firmly agree but maybe for different reasons...

I think getting there would not be the problem. We have newer technology and better understanding and more powerful computers so we can be much more accurate about gravitational assists from large bodies like planets than we did in the 70s. Plus, I think people might think it worthwhile to wait for the satellites to get there, even if we could get there in half the time it did/does for Voyager 1.

The challenge is then to slow down to hold this constellation of satellites at the correct distance. Then you have to synchronize them and position them to hold them, flying in formation, to either micron or nanometer precision. Otherwise you get all sorts of aberrations and distortions.

Then to aim at different objects, you'd have to move the satellite constellation around the sun. Which would be enormous distances at that point. And once they're there, again get into and hold an extremely precise formation.

To get to a significant number of targets, you'd actually probably have to send a full constellation for every single target you want to observe, or maybe group of targets that are in the same proximity.

Then if you wanted to observe targets that aren't on the same plane as our planets, you'd have to find good ways of then placing the targets in orbit around the sun, at that distance, which by some is considered not even inside our solar system, on an orbital plane that is significantly altered from ours. Which that would also require a lot more fuel and careful planning of gravity assists than an orbit that's on the same orbital plane.

Then there's the issue of: look at all the issues we're having with Voyager 1 right now. And how long it takes to get messages to and from it. These would have to go farther... So, realistically, you'd probably have to send several redundant cubesats in case of systems failures, like, a minimum of two redundant cubesats for each member of the constellation.

And then by the time they get there, let's say we use a combination of solar sails and some crazy nuclear propulsion system and they get there in 20 years... Which I think people would see that as worth it... Somehow carrying enough fuel or some future propulsion system that could slow them to stay in orbit... That tech would then be already obsolete. At which point, some other mad astronomer scientist would be like "let's replace them with newer tech!"

It's an extremely novel idea, and we need more like them because maybe we could come up with actual useful ideas by piggy backing off of them... Like... What if instead of placing the cube sats that far out, at the focal length like a refractor, what if we put mirrors in at a much closer spot, in a giant formation and and then reflected those to another satellite that then reflected that to a much closer focal point, effectively making a giant SCT or RCT in space? Many of the same challenges remain, but at that point they're likely more manageable.

 

[billslugg]

"Then you have to synchronize them and position them to hold them, flying in formation, to either micron or nanometer precision. Otherwise you get all sorts of aberrations and distortions."

The Sun's gravity would form a virtual image in space. Each individual craft would be responsible for one pixel, not a complete image, thus spacing accuracy would not be critical.

 

[SpaceCaseAli]

"Then you have to synchronize them and position them to hold them, flying in formation, to either micron or nanometer precision. Otherwise you get all sorts of aberrations and distortions."

The Sun's gravity would form a virtual image in space. Each individual craft would be responsible for one pixel, not a complete image, thus spacing accuracy would not be critical.

So, how many pixels are we talking here then? What's our pixel count? Are we talking 800×600, so, 480,000 satellites flying in formation. I don't see that giving enough detail to make it useful. If we're talking about 1km/pixel (using the Proxima B example).

Maybe 1280x720? 921,600 satellites.

We're not even getting full planets in many cases, much less full stars.

Then, again as I stated before, if one satellite goes down, you now have a hole in your image, or maybe you reconfigure and you now have increasingly smaller images as they eventually fail. So, you'd really need, as I said, to likely have multiple redundant backups for each satellite. I guess, however, if you do it that way, you could send them in waves and have increasingly larger images....

You'd also probably want to power these things via nuclear. There's not enough sun that far out for solar panels. I guess that's okay... But now how much do each of these cubesats cost? How many rockets would we have to launch to put that many that far out?

Honestly, I think we'd probably need to basically make a space based cubesat factory that would source the raw materials from meteors or asteroids or whatever, because that's sooooo much rocket fuel that would be required and the environmental impact of that would be astronomical (if you'll pardon my pun).

Or maybe you'd put that factory on the moon, and build a giant solar/nuclear powered mass driver/rail-gun that would then shoot them into deep space.

That still leaves you with the issue of slowing them down once they reach their destination, which would require a lot of energy.

And while you may not have to have them in perfect formation, they'd still have to fly in a pretty good approximation of a formation.

Either way, this is not happening in our lifetime or probably even the lifetimes of our grandchildren or great grandchildren.

 

[George²]

Yes, I see you understood some of the basis for my comment. Acceleration with chemical rocket engines will not work. Apparently most 99%+ of these traveling probes won't even be able to use gravity assist to accelerate them. They would reach the focal point of the sun in about 200 years. You've already listed that they'll need to carry fuel for ramping up and down and other maneuvers, and that means a lot of fuel and oxidizer. But these probes will be long dead due to lack of electricity. Radioisotope generators don't live that long, at least the current models. At a distance of 542-547 AU, the light from the Sun will be weaker than that of some relatively nearby high-luminosity stars, so it is absolutely pointless to equip the probes with photovoltaic panels. The only way out of the situation would be resolved if we could deliver a very high speed to the probes. At least 150-200km/s to reach the focal point in a reasonable amount of time, and there must be an extremely long-lasting and powerful power source on board. We do not have ready-made solutions, but also the technological possibility to reproduce something sufficiently compact and light. The laser acceleration of probes with solar sails means that the probes are literally no bigger than a matchbox, obviously they will not be able to carry enough fuel even if slow down, let alone drift in and out, when needed to capture objects in different sky sectors. So, they can just take a series of shots, or even just 1-2 on the fly and hopefully hit the moment they're in focus.
Who knows, maybe around 2080-2085 will be possible if civilization survive and make constant high technology progress.

 

[SpaceCaseAli]

Yes, I see you understood some of the basis for my comment. Acceleration with chemical rocket engines will not work. Apparently most 99%+ of these traveling probes won't even be able to use gravity assist to accelerate them. They would reach the focal point of the sun in about 200 years. You've already listed that they'll need to carry fuel for ramping up and down and other maneuvers, and that means a lot of fuel and oxidizer. But these probes will be long dead due to lack of electricity. Radioisotope generators don't live that long, at least the current models. At a distance of 542-547 AU, the light from the Sun will be weaker than that of some relatively nearby high-luminosity stars, so it is absolutely pointless to equip the probes with photovoltaic panels. The only way out of the situation would be resolved if we could deliver a very high speed to the probes. At least 150-200km/s to reach the focal point in a reasonable amount of time, and there must be an extremely long-lasting and powerful power source on board. We do not have ready-made solutions, but also the technological possibility to reproduce something sufficiently compact and light. The laser acceleration of probes with solar sails means that the probes are literally no bigger than a matchbox, obviously they will not be able to carry enough fuel even if slow down, let alone drift in and out, when needed to capture objects in different sky sectors. So, they can just take a series of shots, or even just 1-2 on the fly and hopefully hit the moment they're in focus.
Who knows, maybe around 2080-2085 will be possible if civilization survive and make constant high technology progress.

Gravity assist could happen if you're sending them in packages, basically like cluster bombs.

Or perhaps you build a cubesat factory that would build them out of raw materials and you just load up the raw materials and send it in one giant package. May require less fuel that way because you only have to stop the thing once? Maybe it starts building them on it's way, and shoots them out in the opposite direction to help slow it down when it starts approaching.

I'm being mostly silly and pedantic here, but it's so easy to poke holes in all of these scenarios. And every solution people come up with would have other issues. And every time it gets more and more complicated.

And speaking of complicated, as our electronics gets smaller and smaller, the more susceptible they are to damage from heat and radiation, etc. and we keep putting in more components, which significantly increases the rate of inevitable faults. And we're having issues with Voyager 1.

 

[Unclear Engineer]

I'm still stuck on the one-pixel-per-satellite comment.

I don't see that as correct, but am not familiar with interferometry telescopes.

Still, the telescopes we are currently using to image black holes, etc. seem to be creating images that have more pixels than the number of telescopes used to make them.

 

[Andrew Wright]

So, how many pixels are we talking here then? What's our pixel count? Are we talking 800×600, so, 480,000 satellites flying in formation. I don't see that giving enough detail to make it useful. If we're talking about 1km/pixel (using the Proxima B example).

Maybe 1280x720? 921,600 satellites.

We're not even getting full planets in many cases, much less full stars.

Then, again as I stated before, if one satellite goes down, you now have a hole in your image, or maybe you reconfigure and you now have increasingly smaller images as they eventually fail. So, you'd really need, as I said, to likely have multiple redundant backups for each satellite. I guess, however, if you do it that way, you could send them in waves and have increasingly larger images....

You'd also probably want to power these things via nuclear. There's not enough sun that far out for solar panels. I guess that's okay... But now how much do each of these cubesats cost? How many rockets would we have to launch to put that many that far out?

Honestly, I think we'd probably need to basically make a space based cubesat factory that would source the raw materials from meteors or asteroids or whatever, because that's sooooo much rocket fuel that would be required and the environmental impact of that would be astronomical (if you'll pardon my pun).

Or maybe you'd put that factory on the moon, and build a giant solar/nuclear powered mass driver/rail-gun that would then shoot them into deep space.

That still leaves you with the issue of slowing them down once they reach their destination, which would require a lot of energy.

And while you may not have to have them in perfect formation, they'd still have to fly in a pretty good approximation of a formation.

Either way, this is not happening in our lifetime or probably even the lifetimes of our grandchildren or great grandchildren.

The concept is for ONE spacecraft per target object, manuevering around a roughly 1sq km image. The expectation is that future technology would allow the focal line to be reached in 20-30 years.

 

[Unclear Engineer]

How do yo do long-based interferometry with one satellite? Or, is this now purely optics? And one spacecraft maneuvering around a square kilometer of space to make a picture seems infeasible for a variety of reasons. Position errors, fuel, time required for exposure.

Maybe when we have spacecraft with fusion engines and a lot of time?

Maybe never?

 

[Andrew Wright]

How do yo do long-based interferometry with one satellite? Or, is this now purely optics? And one spacecraft maneuvering around a square kilometer of space to make a picture seems infeasible for a variety of reasons. Position errors, fuel, time required for exposure.

Maybe when we have spacecraft with fusion engines and a lot of time?

Maybe never?

It is not a new idea, it has been studied for years. It is based on complex deconvolution of optical data gathered over months, I think. The positional accuracy required is not high, with maybe 1 sq m per pixel.
I don't recall what technology was assumed for delivery, but not fusion.
Edit: Solar sail with close flyby of the Sun at the trip start was the suggestion.
Google "SGLF Mission".

 

[billslugg]

"So, how many pixels are we talking here then? What's our pixel count? Are we talking 800×600, so, 480,000 satellites flying in formation. I don't see that giving enough detail to make it useful. If we're talking about 1km/pixel (using the Proxima B example)."

The resolution is 1 km at the distance of Proxima Centauri. This is 250,000 AU. The probes would be at 500 AU thus the pixel spacing locally would be about one 500th that or about 2 meters. Pick your field of view, make a giant fish net with 2 meter openings, put a telescope with coronagraph at each junction. The array could be held by just four craft, one at each corner. Paying for it and getting it there are other issues, perhaps intractable at this stage of human evolution. We can't even make a car door that stays open on a hill and won't cut your leg off, so I don't hold out much hope.

 

[Questioner]

Proper terminology would be informative.

Gravity is the re-centering [acceleration] of the center mass of a vibratory object in the direction of an external mass field's center. In most cases that is mutual.

The non-Euclidean geometry of space-time (mass fields) does facilitate gravity but is independent of it.

Light/EM follows that non-Euclidean geometry but doesn't have a vibratory mass, so is unaffected by gravitational acceleration. Light cannot be accelerated.

What is called 'gravitational lensing' would be more accurately called 'geometric lensing' or mass or massfield lensing.

Gravitational acceleration has nothing to do with the geometric lensing.

 

[Classical Motion]

The coherence and quality of bowed light should depend on the stability of the density gradient.
Think mirage. In morning they are still and steady but soon begin to shimmer.

 

[Classical Motion]

I don’t think it can be a telescope. But if we put large blinds in a perpendicular orbit with a 50% duty cycle, timed with earth’s orbit, any life out there that can travel will be on the way.

Would you want to chance it you really think alien life is out there. I don’t know about you, but if I ever was convinced of alien life, I would want to be quiet. And watch and listen for a few millennium.

Do you know why we don’t see any life…… because as soon as it peeps, it’s eaten.

 

[uswine]

While intriguing, this concept comes with several critical and likely insurmountable problems.

First off, it faces the same photon scarcity problem seen in synthetic aperture optical interferometry—collecting enough photons at extreme resolution is a major hurdle. Trying to capture light from a planet orbiting a distant star, which is already dwarfed by its own sun, and then adding in noise from the Sun’s gravitational lensing, could mean waiting centuries just to form a single image. The photons just aren’t there in any practical quantity.

Moreover, the Sun is far from static. It’s constantly undergoing upwelling, downwelling, solar flares, coronal mass ejections (CMEs), and sunspot cycles—all of which create micro-perturbations in its gravitational field. These tiny shifts act like long shadows, and when projected over the 500+ AU focal distance, they’re amplified. This results in smearing and distortions that would make it practically impossible to focus anywhere near the theoretical limit.

This isn’t even something we can correct for like we do with atmospheric turbulence here on Earth. We can’t send a laser to measure the solar distortions and adjust for them in real-time. These solar perturbations are random and uncorrectable, which means the turbulence would essentially be baked into the system.

Another problem is that achieving the required contrast to extract a faint planetary signal from the Sun's photon noise would sharply reduce angular resolution. And don’t forget about signal loss due to photon divergence—the optics of this setup simply aren’t controllable at such extreme distances.

Now, all of this said, using a neutron star instead of the Sun would be much more workable. The gravitational field of a neutron star would be far more stable, and its compact size and extreme gravity would lead to fewer perturbations, making the concept at least theoretically more feasible. Though this will never happen with our understanding of physics.

 

[Andrew Wright]

The optics part of the concept has been computer modelled, in detail, by competent professionals. A convincing dismissal of this idea would need to point out errors in the models. Not that there aren't major challenges; for example, if the target has too much shifting cloud, you are very limited. (A plausible amount of coronal noise has been included in the models, I understand.)
I think the delivery spacecraft is the bigger challenge.

 

[Questioner]

Do you know why we don’t see any life…… because as soon as it peeps, it’s eaten.

Lol.
I'm laughing but not without a twinge of nervousness.
It could true in one form or another.

 

[uswine]

The optics part of the concept has been computer modelled, in detail, by competent professionals. A convincing dismissal of this idea would need to point out errors in the models. Not that there aren't major challenges; for example, if the target has too much shifting cloud, you are very limited. (A plausible amount of coronal noise has been included in the models, I understand.)
I think the delivery spacecraft is the bigger challenge.

take that with a grain of salt ... its clear from understanding the theoretical limits and the dynamics of the system that their model is off. see referenced paper link ...in summary:

Using the Sun as a gravitational lens is practically unworkable due to several insurmountable challenges. The Sun’s dynamic nature—caused by its rotation, solar activity, and multipole gravitational moments like its quadrupole (J2)—creates microgravity perturbations that distort light into complex caustic patterns rather than a smooth Einstein ring. These perturbations result in unpredictable smearing and shifting of the image, and with the focal point over 500 AU away, these distortions are amplified, making the light effectively unfocusable. Unlike Earth's atmosphere, you can’t correct for these solar-induced fluctuations in real time, which means you’re left with a constantly shifting, uncorrectable image—far from the extreme resolution one might hope for.

https://arxiv.org/pdf/2104.08442

https://ntrs.nasa.gov/api/citations/20180002197/downloads/20180002197.pdf

The optics part of the concept has been computer modelled, in detail, by competent professionals. A convincing dismissal of this idea would need to point out errors in the models. Not that there aren't major challenges; for example, if the target has too much shifting cloud, you are very limited. (A plausible amount of coronal noise has been included in the models, I understand.)
I think the delivery spacecraft is the bigger challenge.

the issue of parse photons ... a problem you cannot get around.. few photons ... hi noise...

"The field of exoplanets remains particularly photon-starved even though various detection techniques have uncovered thousands of extrasolar worlds. Often little more is known of such worlds than the most basic parameters, like the period of the planet’s orbit, and the planet-to-star radius ratio or upper limits on the planet’s mass. The number of planets which have been atmospherically characterized using spectra of significant resolution and signal-to-noise are in the ∼10s, and they tend to be giant planets with masses of Neptune or greater "
low contrast https://ar5iv.labs.arxiv.org/html/2407.17741v1

I am not saying it won't be a great telescope. What I am casting doubt on is the angular resolution ...it is far to great considering the dynamic nature of the sun itself. and the noise of the local and remote viewing environment. A realistic view would be welcome. it won't be anywhere near the theoretical limit

s

 

[Andrew Wright]

take that with a grain of salt ... its clear from understanding the theoretical limits and the dynamics of the system that their model is off. see referenced paper link ...in summary:

Using the Sun as a gravitational lens is practically unworkable due to several insurmountable challenges. The Sun’s dynamic nature—caused by its rotation, solar activity, and multipole gravitational moments like its quadrupole (J2)—creates microgravity perturbations that distort light into complex caustic patterns rather than a smooth Einstein ring. These perturbations result in unpredictable smearing and shifting of the image, and with the focal point over 500 AU away, these distortions are amplified, making the light effectively unfocusable. Unlike Earth's atmosphere, you can’t correct for these solar-induced fluctuations in real time, which means you’re left with a constantly shifting, uncorrectable image—far from the extreme resolution one might hope for.

https://arxiv.org/pdf/2104.08442

https://ntrs.nasa.gov/api/citations/20180002197/downloads/20180002197.pdf

the issue of parse photons ... a problem you cannot get around.. few photons ... hi noise...

"The field of exoplanets remains particularly photon-starved even though various detection techniques have uncovered thousands of extrasolar worlds. Often little more is known of such worlds than the most basic parameters, like the period of the planet’s orbit, and the planet-to-star radius ratio or upper limits on the planet’s mass. The number of planets which have been atmospherically characterized using spectra of significant resolution and signal-to-noise are in the ∼10s, and they tend to be giant planets with masses of Neptune.

I am not saying it won't be a great telescope. What I am casting doubt on is the angular resolution ...it is far to great considering the dynamic nature of the sun itself. and the noise of the local and remote viewing environment. A realistic view would be welcome. it won't be anywhere near the theoretical limit

The first paper you link is from 2021, is generally positive, has some modelling, and that work has been built on since.

The second paper, the Landis one, is from 2017, is negative (but not dismissive). I find it unpersuasive. He talks about 100s of spacecraft, which is not the current concept. He worries about photon counts, because he says the image will move over the spacecraft in 40 seconds, limiting integration time. But you'd just match the motion, wouldn't you? (It is a few 100m per second.) That gives you more photons. Other points he brings up seem to be covered by recent modelling.

 

[uswine]

The first paper you link is from 2021, is generally positive, has some modelling, and that work has been built on since.

The second paper, the Landis one, is from 2017, is negative (but not dismissive). I find it unpersuasive. He talks about 100s of spacecraft, which is not the current concept. He worries about photon counts, because he says the image will move over the spacecraft in 40 seconds, limiting integration time. But you'd just match the motion, wouldn't you? (It is a few 100m per second.) That gives you more photons. Other points he brings up seem to be covered by recent modelling.

reasons to be skeptical... too much use of theoretical best case...

>A coronagraph will perfectly block the Sun’s light while allowing the ring of light from the exoplanet to pass through, resulting in minimal signal loss.
Unproven Assumptions: The ability to block the Sun's light perfectly without allowing diffraction effects or scattered light from the corona to leak around the edge of the coronagraph and that edge diffraction from the occulter is assumed to be negligible, which may not be true in practice. The assumption that alignment at 550 AU can be precisely controlled as a system here.

The assumption that the plasma density variations in the Suns corona only slightly perturb the path of light from the exoplanet, introducing minimal phase distortions and blurring. The reality is the corona is dynamic, with significant variations due to solar wind, coronal mass ejections, and other solar phenomena. The models assume this can be correct but this has never been experimentally verified, especially at 550AU.

Additionally, the gravitational lens is expected to amplify the exoplanets light perfectly, improving the signal-to-noise ratio. This ideal case assumes no significant losses due to scattering or absorption and that photon integration is optimal, even with short exposure times and the sparse photon signal from distant exoplanets, which remains an unproven assumption.

I can go on but my point is that these papers are intentionally optimistic and are filled with best case calculations and unproven assumptions. All of which is common in white papers.... I am countering this with some common-sense grounding.

Sure it will work to some degree, but there are many issues here that will drop the resolution back to just a few pixels. The promised clarity is the best possible case of perfectly optimized signal in a noiseless instrument that is near its theoretical performance limits and operated remotely at 550AU.

what is there to be skeptical of ?..piece of cake

 

[Andrew Wright]

reasons to be skeptical... too much use of theoretical best case...

>A coronagraph will perfectly block the Sun’s light while allowing the ring of light from the exoplanet to pass through, resulting in minimal signal loss.
Unproven Assumptions: The ability to block the Sun's light perfectly without allowing diffraction effects or scattered light from the corona to leak around the edge of the coronagraph and that edge diffraction from the occulter is assumed to be negligible, which may not be true in practice. The assumption that alignment at 550 AU can be precisely controlled as a system here.

The assumption that the plasma density variations in the Suns corona only slightly perturb the path of light from the exoplanet, introducing minimal phase distortions and blurring. The reality is the corona is dynamic, with significant variations due to solar wind, coronal mass ejections, and other solar phenomena. The models assume this can be correct but this has never been experimentally verified, especially at 550AU.

Additionally, the gravitational lens is expected to amplify the exoplanets light perfectly, improving the signal-to-noise ratio. This ideal case assumes no significant losses due to scattering or absorption and that photon integration is optimal, even with short exposure times and the sparse photon signal from distant exoplanets, which remains an unproven assumption.

I can go on but my point is that these papers are intentionally optimistic and are filled with best case calculations and unproven assumptions. All of which is common in white papers.... I am countering this with some common-sense grounding.

Sure it will work to some degree, but there are many issues here that will drop the resolution back to just a few pixels. The promised clarity is the best possible case of perfectly optimized signal in a noiseless instrument that is near its theoretical performance limits and operated remotely at 550AU.

what is there to be skeptical of ?..piece of cake

I don't think informed advocates think anything other than "this will be difficult", but they think it may be possible. I'll just add that the expected image integration time is of the order of years, with a lot of processing of the data. Brief observations would be useless. The spacecraft has to manuever to keep inside the image.