First Multi-Planet System Around a Sun-Like Star Imaged

This image, captured by the SPHERE instrument on ESO’s Very Large Telescope, shows the star TYC 8998-760-1 accompanied by two giant exoplanets. This is the first time astronomers have directly observed more than one planet orbiting a star similar to the Sun. The image was captured by blocking the light from the young, Sun-like star (on the top left corner) using a coronagraph, which allows for the fainter planets to be detected. The bright and dark rings we see on the star’s image are optical artefacts. The two planets are visible as two bright dots in the centre and bottom right of the frame.

The universe is teeming with exoplanets, but we’ve only been able to detect a small fraction of them. We’ve directly imaged just a handful, but you can add two more to the tally today. The European Southern Observatory has captured a pair of exoplanets with the Very Large Telescope array (VLT), marking the first time scientists have gotten a picture of a multi-planet system around a sun-like star. 

Astronomers usually spot exoplanets using two different methods. There’s the radial velocity approach, which checks stars for small “wobbles” caused by orbiting planets. Most newer instruments rely on the transit method, which monitors stars for small dips in luminance that indicate a planet has passed in front of them. We can learn some basic details about exoplanets from these techniques, but actually seeing an alien world? That’s very rare because planets are so dim compared with the stars they orbit. In this case, scientists were specifically scanning nearby sun-like stars to see if any of them had visible exoplanets. 

The VLT is one of the few observatories capable of imaging exoplanets, and even it can only do so under very specific circumstances. The star known as TYC 8998-760-1 is about 300 light-years away, which is practically in our own backyard (on a galactic scale). The two gas giant planets visible in the frame are also easy to spot compared with most exoplanets. The inner planet is 12 times more massive than Jupiter and 160 times farther from TYC 8998-760-1 than Earth is from our sun. The outer planet is 320 times farther out than Earth and has a mass about six times that of Jupiter. 

The SPHERE instrument on the VLT.

Being so large and far away from the star made these worlds easier to spot, but they’re still extremely faint. The ESO was only able to image them with the help of its Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) instrument. That’s the same tool that revealed the beginnings of a planetary system earlier this year. SPHERE blocks light from the star using a device called a coronagraph, allowing the telescope to focus on the nearby planets. 

This star is a very young version of our own sun, a mere 17 million years old. Understanding how this solar system is forming could shed light on our own little corner of the universe. Further observations with the VLT and the upcoming Extremely Large Telescope will help astronomers determine if these planets formed where they are or if they migrated out. There may also be lower-mass planets in this solar system we cannot currently detect — maybe even some primordial Earth-like planets.

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