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First images from Euclid are in

(dlmultimedia.esa.int)
534 points mooreds | 11 comments | 21 Oct 24 20:15 UTC | HN request time: 1.126s | source | bottom
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lfmunoz4 ◴[22 Oct 24 00:22 UTC] No.41909953[source]▶
600x zoom didn't seem to help from the 150x zoom. Wonder if we will ever be able to see actual planet surfaces or we need some other technology to do that, i.e, we should have small satellites every 10 light years. but this map is amazing and a good step forward.

Edit: Was just thinking that image does us tells us something i.e, there no large artificial structures or billboards anywhere we can see. Maybe I watch too much sci-fi but honestly would have expected someone to build some huge structure around a star or planet, would be disappointing if no one does.

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1. stouset ◴[22 Oct 24 00:29 UTC] No.41909980[source]▶
There is zero way to optically resolve an exoplanet’s surface without something like a gravitational lens.
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2. xpl ◴[22 Oct 24 01:35 UTC] No.41910325[source]▶
Can't we build a giant optical interferometer in space by sending multiple telescopes out there?
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3. frabjoused ◴[22 Oct 24 02:42 UTC] No.41910695[source]▶
If light is hitting it, can you explain why not?
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4. recursive ◴[22 Oct 24 03:20 UTC] No.41910903[source]▶
I don't know much about it, but my guess is that 0* photons from that planet make their way into any given telescope lens in a given day.
5. thrtythreeforty ◴[22 Oct 24 03:35 UTC] No.41910961[source]▶
The naïve optical instrument will be diffraction limited. The resolving power of a lens, basically how "sharp" the resulting image will be, goes down as you decrease the size of the aperture relative to the focal length (that is, as the f-stop number goes up).

A telescope that could zoom into an exoplanet would have an f value of a kajillion or so.

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6. mlyle ◴[22 Oct 24 03:53 UTC] No.41911032[source]▶
Possibly, but the challenges to do so are immense. Using the sun as a giant gravitational lens seems much more tractable.
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7. cvoss ◴[22 Oct 24 04:45 UTC] No.41911269{3}[source]▶
Really? I wouldn't think the sun is nearly massive enough to do what would be required here. Stars visible near the edge of the Sun appear in slightly different spots from their actual locations. If there was a distant planet directly behind the Sun whose light were focused back to an image on our side of the Sun, you'd have to get really far back from the Sun to resolve the image, no? And furthermore, it's exceedingly difficult to orient such an apparatus to look in the desired direction; you are beholden to the orbital mechanics of your viewing satellite as it plods along.

Whereas, multi-site telescopes spread across the Earth have already been demonstrated as a feasible technology (recall the black hole images). It is well within our ability to set up a constellation of satellites, perhaps spanning a few of the Earth-Sun Lagrange points.

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8. stouset ◴[22 Oct 24 06:04 UTC] No.41911612{4}[source]▶
> Really? I wouldn't think the sun is nearly massive enough to do what would be required here.

You "just" need to get far enough away (~600AU). Interferometry is extremely difficult to pull this off with and it’s further complicated by the host star being so much brighter than the exoplanet.

See this recent Fraser Cain interview with Dr. Slava Turyshev:

https://www.youtube.com/live/lqzJewjZUkk?si=WWNdR1PESYzD0d4X

9. stouset ◴[22 Oct 24 06:07 UTC] No.41911626{3}[source]▶
You’d need a 90km aperture to get a one pixel image of an Earth-sized exoplanet at 100ly.
10. mlyle ◴[22 Oct 24 06:12 UTC] No.41911646{4}[source]▶
https://en.wikipedia.org/wiki/Solar_gravitational_lens

> you'd have to get really far back from the Sun to resolve the image, no?

Yah, a few hundred AU.

> you are beholden to the orbital mechanics of your viewing satellite as it plods along.

Yah, any mission like this -- interferometry or gravitational lensing -- is going to be super long and hit very few targets.

> Whereas, multi-site telescopes spread across the Earth have already been demonstrated as a feasible technology

Yah, at radio frequency while pinned to a common rock. The wavelength of visible light is hundreds of nanometers and we're talking across massive distances and significant gravity gradients and even relativistic corrections. The "big" space interferometers currently being considered are in the mid-infrared (e.g. longer wavelengths) across baselines of hundreds of meters.

All of these ideas are really hard.

11. skykooler ◴[22 Oct 24 06:20 UTC] No.41911698{4}[source]▶
Yes, you'd need to get quite far from the Sun to use it as a lens - about 650 AU is where it starts becoming practical. It would also not be re-orientable, so any "telescope" launched to that location would only be able to observe a single target. (But, notably, it is far easier to send a probe to a far point in our own solar system than it is to send it to another star entirely.) There's a paper that goes into much more detail at https://arxiv.org/pdf/1604.06351

So why not use interferometry instead? Well, it has some significant drawbacks. For example: the Event Horizon Telescope used radio telescopes - and pretty much had to, due to how interferometry works: you need to be able to compare the phase shifts between the multiple telescopes, which means you need to be able to sample the signal faster than the radio frequency you're using and record it. The EHT records 64 gigabits per second for each telescope, and then all this data needs to be combined to compute the resolved image. This amount of data would be problematic for space-based telescopes - even on Earth, it was not practical to send multiple petabytes over the internet, so it was saved to hard drives which were shipped by truck instead. This isn't practical in space, so you would need to transmit the data by radio, which means you'd end up with some crazy ratio of thousands of hours of transmitting for every one hour you spend recording.