Just over 300 light-years away is a star that’s a lot like a very young version of our Sun, with multiple exoplanets orbiting it. That’s an interesting find in itself. But what makes the system truly dazzling is that it just became the first of its kind to be directly imaged, planets and all.
On the night of 16 February 2020, astronomers using the Very Large Telescope in Chile were able to obtain direct observations of two enormous exoplanets on extremely large orbits around the star named TYC 8998-760-1.
Directly imaging exoplanets is challenging, to say the least. They are very dim compared to their host stars, and very far away from us. Most of the over 4,000 exoplanets confirmed to date have only been detected via indirect means – such as faint, regular dips in the star’s light as the exoplanet passes in front of it, or a slight wobble in the star’s position due to the exoplanet’s gravity.
Because these signals are easier to pick up when the planet is big and close to the star, most of the confirmed exoplanets are big and close to their stars. But it’s hard to get a clear picture of exoplanets in close orbits because their host stars tend to shine much brighter than them, and planets in older systems that orbit far away are too cool for infrared detection.
So far, only a few tens of exoplanets and two other multi-planet systems that orbit stars very different from the Sun have been directly imaged.
But last year, a group of astronomers led by Alexander Bohn of Leiden University in the Netherlands found a strange planet orbiting TYC 8998-760-1. They did this by taking direct pictures of the star.
It was a gas giant about 14 times as big as Jupiter and about 160 astronomical units away from its star. To give you an idea of how far away that is, Pluto is 39 astronomical units from the Sun on average when it goes around it.
So Bohn and his colleagues used the exoplanet-imaging SPHERE instrument on the Very Large Telescope to get a better look. They took a number of observations from the past year and added them to data from 2017.
