This episode is sponsored by 80,000 Hours. 80,000 Hours is a nonprofit that aims to help people have a positive impact with their career.

Head to 80000hours.org/scishowspace to start planning a career that can help solve one of the world’s most pressing problems. [♪ Intro] I would like for humans to take a picture of an exoplanet. I mean, we can image them.

By which I mean, you can see the little points of light that are planets in other solar systems. So that’s kind of a picture. But I really want to see one.

You know, like we’re flying up to it in a sci-fi movie. I want to see the clouds and the continents and that, of course, is impossible. Except it’s not.

We just need bigger, badder telescopes. And you’d be surprised how creative astronomers can get when it comes to coming up with them. A telescope is really just two things: some way of focusing light, and some way of detecting that light.

This can be as simple as, say, a lens and Galileo’s eyeball. These days it’s more along the lines of mirrors and tons of different cameras and detectors. In theory, though, to get better and better photographs of distant objects, you just need a bigger lens.

Or a bigger mirror. Just a system to collect more light. Galileo’s telescope had a 38 millimeter lens.

And from there we’ve scaled up to the James Webb Space Telescope’s 6.5 meters in space, with even larger mirrors on the ground. And currently under construction in Chile, the appropriately named Extremely Large Telescope will have a 39 meter mirror! But those are just peanuts compared to some “telescopes” we’re already using.

See, there’s no reason the detector and the lens of a telescope have to be in one piece. In theory, you could have a telescope that is very, very, very long with a detector literal light-years away from the lens. And, indeed, those telescopes exist… thanks to gravity.

Gravity warps space. Specifically, very massive objects distort space around them. And warping space causes light passing through it to bend as well, and bending light is what the lens of a telescope does.

And, in very particular situations, this effect creates an accidental telescope. This is an Einstein ring: a weird ring around a massive object in the sky. The stuff you can see around that star is not actually there, it’s behind the star.

WAY behind it. The light coming from those extremely distant objects is being warped by the divot the star makes in space, allowing us to see stuff that is very very far away as if it were much closer. Gravity is warping the space, so we call this gravitational lensing.

These accidental telescopes are how we know a ton of stuff about our universe, including seeing some of the most far-off, and therefore earliest, stuff in the universe. In 2022, for example, astronomers wrote that they’d actually used gravitational lensing to spot the oldest star ever seen. The James Webb Space Telescope will be able to use gravitational lensing, effectively pointing at telescope at another telescope to make some seriously superpowered images, potentially seeing some of the very first stars to ever exist in the universe.

Many objects, such as stars, galaxies, and even black holes, can create a gravitational lensing effect, but almost none of them are useful because we cannot control these telescopes. The detector, which is us, and the “lens”, which is the star, have to line up perfectly with the object we’re observing… and all by pure astronomical chance. Luckily, even though space is very empty, it’s also very big, which means there are lots of opportunities to get lucky.

We’ve identified thousands of these alignments that have allowed us to discover all kinds of cool things. But we don’t really have a choice about what’s being lensed. Except we haven’t even really gotten to the cool part yet, because in the future, we might.

Which would let us use gravitational lensing to do all kinds of things, including taking an actual photograph of an exoplanet. Photographs could show us if they have continents, oceans, clouds… In 2021, an article called “Image recovery with the solar gravitational lens” was published in the journal Physical Review D. And by “solar” they don’t mean any old star out there.

They mean our Sun. This is just the latest proposal for a solar gravitational lens in an idea that goes back decades. What’s different about this one is that it considers what is possible with current technology and draws the conclusion that we already have the computing capacity to take pictures with solar gravitational lensing, if not the spacecraft.

But all you’d have to do there is launch a detector of some sort and line it up with the Sun and whatever it is you want to see. Of course, this is not without its challenges. Let’s hit some of the big ones the authors identified.

First, the sun doesn’t have a perfectly sharp edge. It has an atmosphere called the corona, and the corona would block a lot of what we’d like to see. So we would need sophisticated ways to correct for that.

Second, we need to put our detector far enough away from the sun to actually use it as a gravitational lens. This… is far away, around 550 astronomical units from the sun. That’s 550 times the distance between the Sun and the Earth.

Voyager 1, the most distant spacecraft we have ever sent out into space, is a bit more than 150 AU from the sun. Third, these telescopes would, in effect, be single use. You need them to be perfectly aligned with whatever they’re observing.

So if we want to observe the Alpha Centauri system, we’d send out a telescope for the Alpha Centauri system. If we wanted to observe the TRAPPIST-1 system, we’d need a totally different mission. But the big win of this study was that they actually offered a simulation of what the Earth would look like if it was about 4.3 light years away and we were able to take a picture of it this way.

This is what we would get before correcting for any fuzziness from the Sun’s corona, and the fact that it’s not a perfect sphere. This is what we would get after correction. It seems impossible, but this is likely a thing that humanity really could do!

Probably not super soon, though. There are a lot of challenges to overcome, and probably a number that are yet to be uncovered. Even if a solar gravitational lens was built, it would take, with current technology, at minimum, 17 years to arrive at the proper focal distance to start doing astronomy.

And I really want to see those pictures, so… tick tock, astronomers. Thanks for watching this episode of SciShow Space, which was brought to you by 80,000 Hours. 80,000 Hours is a nonprofit that aims to help people have a positive impact with their career. Your career is on average 80,000 hours long, so it’s a pretty big opportunity to make a difference.

They offer a bunch of free resources to help you build your career and create the impact you want to see in the world. They have a job board that lists over a thousand high-impact roles that are currently accepting applications. They even have a team of impartial career advisors who give one on one calls.

That’s right, you can apply to have an hour-long career development video call with a real human and it’d be completely free. Because they just want to help you make a difference! Click our link in the description or go to 80000hours.org/scishowspace to be sent a free copy of their in-depth career guide, as well as to sign up for their newsletter to get updates on their research and new job opportunities. [♪ Outro]