This image shows the star TYC 8998-760-1 accompanied by two giant exoplanets, TYC 8998-760-1b and TYC 8998-760-1c (both in the right foreground). Image: ESO/Bohn et al
Our first ever sighting of a sun-like star and two exoplanets is a snapshot of an environment similar to our solar system, but at a ‘much earlier stage of evolution’.
Despite our catalogue of known exoplanets now numbering in the thousands, very few have ever been directly imaged. Now, astronomers using the European Southern Observatory’s (ESO) Very Large Telescope (VLT) have revealed the first image of two such planets orbiting a distant, sun-like star.
The direct imaging of more than two exoplanets has only ever been achieved twice before, but their parent stars were considerably different from our sun.
Writing in The Astrophysical Journal Letters, the team of astronomers, led by Alexander Bohn of Leiden University in the Netherlands, said the sighting was made in a planetary system known as TYC 8998-760-1, which is approximately 300 light years away.
The two planets in the new image released today (22 July) are shown as bright points of light distant from their parent star. It was achieved by taking different images at different times to distinguish the planets from background stars.
These planets are gas giants at a distances 160 and 320 times the Earth-sun distance. This is much further than our own gas giants of Jupiter and Saturn, which lie at around five and 10 times the Earth-sun distance, respectively.
‘Implications for history of our solar system’
Also, both of these exoplanets are much heavier than their solar system equivalents, with the inner planet having 14 times Jupiter’s mass and the outer one being six times greater. While similar in make-up to our own sun, the star TYC 8998-760-1 is an infant version just 17m years old.
Bohn said the discovery is a snapshot of an environment similar to our solar system, but “at a much earlier stage of its evolution”.
The astronomers used VLT’s Sphere instrument – which blocks the bright light from the star using a device called a coronagraph – to see the much fainter planets. While older planets, such as those in our solar system, are too cool to be found with this technique, young planets are hotter and so glow brighter in infrared light.
Future imaging of the system using ESO’s in-development Extremely Large Telescope (ELT) will allow astronomers to test whether these planets formed at their current location distant from the star or migrated from elsewhere.
“The possibility that future instruments, such as those available on the ELT, will be able to detect even lower-mass planets around this star marks an important milestone in understanding multi-planet systems, with potential implications for the history of our own solar system,” Bohn said.
