Episode for August 14th, 2023 Download

One of the reasons we’ve created Exoplanet Radio is that Exoplanets are awesome. The idea that there are planets in orbit around stars outside our solar system - and even rogue planets that do not orbit a star meandering through interstellar space - is one that cannot help but capture our imagination.

The thing is, finding them is very hard. They are small and dim compared to stars so we need to rely on indirect methods to see them like looking for dips in brightness or a wobbling star, or, in the case of rogue planets with no stars, tiny flashes of light from background stars.

But ideally, we’d like to see them directly, in our telescopes. Is that possible? You probably guessed I wouldn’t have brought up the question if the answer wasn’t ‘yes’.

So far, we have discovered over 5000 exoplanets, using transit, radial velocity and microlensing methods. But there is another way to find exoplanets that has only recently been possible: by directly seeing them with our eyes. This is unimaginatively called the direct imaging method, and has revealed some amazing results.

So here’s the scenario: We see all planets - including those in our solar system - in reflected light from the star. Starlight shines on a planet and is reflected to our telescopes. Now imagine trying to see a tiny speck of dust next to a bright light bulb. That is the challenge of direct imaging planets light years away.

The star’s light is so dazzling that it blinds us from seeing the planet’s faint glow. To fix that, astronomers use a special device called a coronagraph, which blocks out the star’s light and lets us see the planet’s light. It is like putting a finger over the light bulb, so we can see the dust speck.

Using this method, astronomers have captured some stunning images of exoplanets, such as 2M1207b, the first exoplanet to be directly imaged, and also the first one to orbit a brown dwarf star, a failed star that is too small to shine. We have also seen four planets orbit around the young star HR8799, in a mesmerizing choreography of motion.

Direct imaging is not only beautiful, but also powerful. It can tell us more about the exoplanets than any other method. It has the potential to show us their colors, shapes, sizes, and even their weather patterns. It can reveal their oceans, continents, and maybe even signs of life. It can open our eyes to new worlds and new possibilities.

Direct imaging is still a young and evolving technique, but it has already shown us some of the most incredible sights in the universe. As our technology improves, we will be able to see more and more exoplanets with direct imaging, and learn more about them. We will be able to witness the diversity and beauty of these distant worlds, and maybe even find one that is like our own.