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COMMENT PAGE FOR:
HTML A solar gravitational lens will be humanity's most powerful telescope (2022)
tzs wrote 1 hour 35 min ago:
Here's a PBS Space Time episode [1] from a couple years ago that
describes a couple different proposals for how to do this that take
quite different approaches. It starts getting into the specifics of
those approaches at 7 minutes in if you don't need the introductory
material.
HTML [1]: https://www.youtube.com/watch?v=4d0EGIt1SPc
pfdietz wrote 2 hours 28 min ago:
One could also lens neutrinos using the Sun's core. Because neutrinos
are not absorbed by the Sun, there is a critical offset from the core
where they are maximally focused. This would form a caustic, and would
cause increased magnification of the neutrino signal at that focal
distance.
est31 wrote 1 hour 47 min ago:
The sun is the biggest neutrino source in the sky. So we'd need some
way to filter out neutrinos that are not from the sun, like we do
with various photon telescopes.
Furthermore, we can barely detect neutrinos. Building neutrino
detectors is extremely challenging. Usually they are extremely
massive and surrounded by lots of rock (even more massive). We'd have
to get all that mass to the focal point of the observatory which is
extremely far away.
Lastly, the gravitational field inside the sun is much different than
outside. In fact, the field is strongest at the surface (or slightly
below, as it doesn't have equal density). The further inside you go,
the more parts of the sun start pulling you outside, until you reach
the center of mass, where the gravitational forces cancel out.
JoeAltmaier wrote 2 hours 15 min ago:
What non-uniform field of neutrinos would one expect? I seem to
recall that neutrinos come from every direction. Perhaps some stellar
event like a nova? Otherwise the image would be the same everywhere,
as the sun is relatively uniform.
holografix wrote 3 hours 17 min ago:
Is this a similar principle to the concept in the 3 Body Problem series
of books? As in, how one of the main characters is able to boost the
transmission power of an earth bound antenna
koolala wrote 3 hours 21 min ago:
This is almost the plot of Three Body Problem. Could we use a Solar
Gravitational Lens in reverse and project signals out of the lens in
reverse?
sbierwagen wrote 1 hour 16 min ago:
Protector by Larry Niven (1973) also features a gravity-powered
telescope.
tombh wrote 3 hours 56 min ago:
Christian Ready made a great video on his Youtube channel, Launch Pad
Astronomy, about NASA's plans for a solar gravitational lens. It's got
some great graphics and visualisations, and is accessibly narrated. I
was inspired and learnt a lot of new ideas. [1] (23 minutes)
HTML [1]: https://www.youtube.com/watch?v=NQFqDKRAROI
cryptoz wrote 3 hours 57 min ago:
Iâve put this in my âother ideasâ section in YC applications for
a couple rounds now. No luck yet.
Would love to send 1,000 probes to 550AU+ out in order to observe
1,000+ ânearbyâ exoplanets, hopefully find life, make contact,
start tradeâ¦haha. Or otherwise defend the solar system from invaders
that are perhaps already on the way!
Maybe YC rejects me specifically because I put that thereâ¦hm.
dylan604 wrote 1 hour 22 min ago:
What kind of ROI would attract a VC to this kind of project? How
could they monetize it?
Would each image created be proceeded by ads that you can skip after
5s or would they be unskippable? Data harvesting is kind of the point
of the platform, but maybe they could track that data and get the
PII/deanonymized information? "This user spent 104 hours continuously
staring at the sun. Maybe they would be interested in sunglasses, or
maybe some sun block"
bensandcastle wrote 3 hours 37 min ago:
how much analysis have you done on this? I'm working on a series
around Kardashev II work - space solar, asteroid mining, dyson
spheres and the real work that is happening to support this now.
contact me if you'd like to discuss - @bensand on X
consumer451 wrote 4 hours 9 min ago:
The most complete plan for this was proposed by JPL's Slava Turyshev
and team. It has been selected for Phase III of NASA Innovative
Advanced Concepts. [0]
> In 2020, Turyshev presented his idea of Direct Multi-pixel Imaging
and Spectroscopy of an Exoplanet with a Solar Gravitational Lens
Mission. The lens could reconstruct the exoplanet image with ~25
km-scale surface resolution in 6 months of integration time, enough to
see surface features and signs of habitability. His proposal was
selected for the Phase III of the NASA Innovative Advanced Concepts.
Turyshev proposes to use realistic-sized solar sails (~16 vanes of 10^3
m^2) to achieve the needed high velocity at perihelion (~150 km/sec),
reaching 547 AU in 17 years.
> In 2023, a team of scientists led by Turychev proposed the Sundiver
concept,[1] whereby a solar sail craft can serve as a modular platform
for various instruments and missions, including rendezvous with other
Sundivers for resupply, in a variety of different self-sustaining
orbits reaching velocities of ~5-10 AU/yr.
Here is an interview with him laying out the entire plan.[2] It is the
most interesting interview that I have seen in years, possibly ever.
[0] [1] [2]
HTML [1]: https://en.wikipedia.org/wiki/Slava_Turyshev#Work
HTML [2]: https://www2.mpia-hd.mpg.de/~calj/sundiver.pdf
HTML [3]: https://www.youtube.com/watch?v=lqzJewjZUkk
bloopernova wrote 4 hours 49 min ago:
Sort of related question:
Would space telescopes use interferometry to get a clearer picture?
If we had thousands of telescopes spread across the solar system, what
sort of images of distant stars/planets/galaxies could we gather? Would
such an array be scientifically worth making in our distant future, or
does it suffer from diminishing returns?
jiggawatts wrote 3 hours 51 min ago:
There have been plans drawn up for space telescopes flying in
formation to do the same kind of interferometry thing as the Keck
observatory.
The problem is that even far from the Earth, there are tiny but
significant forces pushing the space telescopes around. Solar wind,
outgassing, gravitational influences from planets, etc...
The precision required to maintain formation is... challenging.
E.g.:
HTML [1]: https://arxiv.org/abs/1907.09583
mmaunder wrote 4 hours 55 min ago:
Spoiler: the focal point is 3.5x the distance to Voyager 1.
trhway wrote 4 hours 20 min ago:
if to use existing nuclear reactor tech and already existing, as
tested by NASA (and drives Starlink satellites), ionic drive - about
3500 ISP - that focal point would take about 10 years to reach. I
hope that SpaceX flights to Mars will, after the probably first
chemical ones, be done using ionic drive with solar as it is just
faster, thus getting tech developed and with adding nuclear for
beyond Mars - so in 10-20 years we'll have the stuff flying. (note
that "small" reactors - 100MW - we have for submarines, and with MS,
ORCL, GOOG, AMZN getting into nuclear we'll have such small reactors
productized into normal commercial use which will simplify space use
too as commercial use require higher reliability/etc. compare to
military)
kibwen wrote 3 hours 36 min ago:
> that focal point would take about 10 years to reach
Is this taking into account the time needed to slow down?
trhway wrote 3 hours 27 min ago:
It is the napkin scale, not precise mission calculation. Doing 2
stages you can get faster, doing higher voltage you can get
faster, etc. Slow down would of course take time and delta-v,
changing observation station would also take them, etc. What
interesting is that increasing Isp 10x seems to be doable with
the today's/near-future tech, and that would even allow 1000 year
mission to the closest star using 3 stages (unfortunately even my
napkin breaks though when trying to stretch to the 100 years
mission to the star using the today's/near-future tech).
kibwen wrote 2 hours 39 min ago:
Right, but assuming constant acceleration, there's an enormous
difference between accelerating all the way to the target and
only accelerating halfway to the target, and then decelerating
the rest of the way.
ndheebebe wrote 1 hour 30 min ago:
Silly question. Can you do a "drive by". In other words not
slow down. How much time you need to "take the photo". I am
using terms like Randall in Thing Explainer here!!
Maybe it has further missions in deep space after that. Or
look in other directions and use other stars.
kibwen wrote 58 min ago:
I've actually just finished watching the video linked
elsewhere in this thread and a drive-by is exactly what
they propose, using multiple telescopes launched on
staggered schedules in order to make repeated observations
and gradually refine the image.
trhway wrote 2 hours 10 min ago:
>but assuming constant acceleration
it isn't realistic assumption. Until you're talking pure
solar, the amount of acceleration is limited by the reaction
mass available. Actually to get there in 10 years with the
Isp 3500 3 stages are necessary, or better the Isp should be
increased 2x-4x - still seems doable - to get with like 2
stages with realistic [today] parameters of the reactors/etc.
freeqaz wrote 5 hours 20 min ago:
Is there anything stopping you from putting 2+ satellites out "closer"
but in the path of the lensed light, capturing the light
simultaneously, and then resolving the image via async computation
later? I think this is called interferometry and I know it's hard
because you need _very_ precise timing, but I'm curious if that would
be possible or not. (Maybe you can get the timing in sync with atomic
clocks, or by sending a laser to both from a central point that lets
them keep time with some very tight tolerance?)
Weird idea but I wonder if there are ways to take this from "crazy
tech" to "hard tech".
cyberax wrote 3 hours 21 min ago:
> Is there anything stopping you from putting 2+ satellites out
"closer" but in the path of the lensed light
The Sun. Literally.
Satellites have to be that far for the Einstein ring to be bigger
than the apparent size of the solar disk.
Edit: to make it a bit more clear, the gravitational lens does not
quite behave like a normal lens. Instead, you see the light from
_behind_ the object. So if you're too close to the lensing object so
that the Einstein ring is not larger than it, you'll just see a part
of the object to be a bit more bright.
Also, the gravitational lens does not actually _focus_ the image, it
distorts it into a band around the lensing object.
Dalewyn wrote 2 hours 50 min ago:
>to make it a bit more clear, the gravitational lens does not quite
behave like a normal lens. Instead, you see the light from _behind_
the object.
Or to put it another way: A gravity lens bends space so that the
light from behind an object curves around it while travelling
straight.
tbrownaw wrote 1 hour 37 min ago:
"Normal" lenses bend light more strongly farther out towards the
edges. Gravitational lensing is shaped differently.
Dalewyn wrote 38 min ago:
The point is you aren't bending the light, no the light is
travelling straight.
You are bending the dimension, the light travels straight
through a bent dimension thus coming out curved.
I think that's mindblowing.
chgs wrote 4 hours 33 min ago:
On a cosmic scale what does simultaneously mean? Two object in a
distinct orbit will be in different planes of reference
hatthew wrote 3 hours 23 min ago:
Presumably it means that two light rays that leave the same point
on the planet simultaneously (but going in slightly different
directions) arrive at the two telescope satellites simultaneously
colechristensen wrote 5 hours 9 min ago:
The precision you need for interferometry depends on the wavelength,
and being able to do this over astronomical distances at visible
wavelengths would indeed be a challenge. I think the scale is timing
more accurate than 0.1 nanoseconds and distance accuracy on the order
of 100 nanometers. Near those orders of magnitude at least and over
astronomical distances that might be measured in AU.
Then again the precision of the gravitational wave instruments
measure distance on the order of the width of a proton, so who knows.
Terrestrial infrared and optical interferometry telescopes are on the
bleeding edge right now.
vlovich123 wrote 3 hours 18 min ago:
"Boring" cesium atomic clocks can do 50 ps per day with the best
cutting edge optical clocks coming in at ~739 fs per day. Optical
clocks would only need to resynchronize once every ~ 135 days while
cesium clocks would need to do it every 2 days to get 0.1ns of
accuracy.
I think the bigger challenge may be how you would transport the
clocks after synchronization to maintain it across astronomical
distances since they're very sensitive to any kind of acceleration.
Since you have to regularly re-synchronize them in space anyway,
that feels like the engineering problem you'd have to solve - how
do you synchronize two atomic; the current record is synchronizing
to within 0.32fs at a distance of 300km [1]
HTML [1]: https://spectrum.ieee.org/atomic-clock-femtosecond-accurac...
asdfman123 wrote 5 hours 41 min ago:
Could we do a less extreme version of this with a planet in the solar
system? Or would a probe have to be too far away from it?
mbrubeck wrote 4 hours 55 min ago:
If you use Earth, you can use atmospheric lensing (rather than
gravitational) to get a focal point inside the EarthâMoon system:
HTML [1]: https://www.scientificamerican.com/article/earth-could-be-a-...
yodon wrote 5 hours 34 min ago:
A planet would be a weaker lens so you'd have to be even farther
away, and you'd have less collecting area as well.
worldsayshi wrote 5 hours 35 min ago:
Cool worlds YouTube channel has a great video about Earth sized
telescopes:
HTML [1]: https://youtu.be/jgOTZe07eHA?si=0veG99yEbLQTKs4I
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