Stellar snapshot: astronomers have photographed a sun-like star with two large exoplanets – it is the first direct image of such a multi-planet system around a strange sun. The star TYC 8998-760-1 is around 300 light years away from us and is much younger than our sun. The telescope image is therefore almost a review of the past of our own star.
Astronomers have discovered thousands of exoplanets, including many potentially life-friendly worlds in our immediate neighborhood. Many stars, like the sun, are also orbited by several planets, including our neighboring star Proxima Centauri with two planets or the red dwarf TRAPPIST-1, which is only 40 light years away, with the same seven planetary satellites.
But despite this abundance of alien worlds – photos of exoplanets have so far been rare. Most of them are too far away and too dark to be imaged even with the most powerful telescopes. And portraits of stars with multiple planets are even rarer: So far, only two such systems have been observed directly and both belong to stars that differ significantly from our sun.
Younger sister of the sun
Now astronomers led by Alexander Bohn from Leiden University have succeeded for the first time in photographing a sun-like star with several planets. They took this stellar snapshot using the Very Large Telescope (VLT) of the European Southern Observatory in Chile. The SPHERE instrument of this telescope blocks the bright light of the star with a so-called coronograph, so that it no longer outshines the planets. This makes them visible in infrared light.
The now photographed planetary system is about 300 light years away from us in the southern constellation Musca (fly). At only 17 million years old, the star TYC 8998-760-1 is a much younger “twin sister” to our sun. “This discovery is a snapshot of an environment that is very similar to our solar system, but at a much earlier stage in its development,” explains Bohn.
Two gas giants in wide orbits
The photo shows the young, sun-like star TYC 8998-760-1, which is accompanied by two bright, diagonally positioned points of light. They are two young gas giants orbiting their stars at a distance of 160 and 320 astronomical units. For comparison: the gas planets Jupiter and Saturn are only five or ten astronomical units away from the sun.
The two planets around TYC 8998-760-1 are also much heavier than our “domestic” gas giants: the inner exoplanet is 14 times the mass of Jupiter and the outer is still six times the mass of Jupiter. It was only this combination of size, large distance from the star and the heat radiation from these planets, which was still intense due to their young age, that made it possible to see them in the telescope.
Looking back at the history of our solar system
Observations of recent versions of our sun and the solar system help astronomers to better understand the past of our star and planet system. At the same time, TYC 8998-760-1 offers the perfect opportunity to research the dynamic development of young gas giants in such systems. Because according to common theory, many of these gas planets only migrate into their final orbit around their star – also Jupiter has changed its orbit.
The researchers hope that future telescopes such as NASA’s James Web space telescope, which will start in 2021, or ESO’s Extremely Large Telescope, which is currently under construction, will provide further insights into the planetary system of the young sun TYC 8998-760-1 – and perhaps even more planets discover.
“The possibility that future instruments will be able to discover even less massive planets around this star is an important milestone for the understanding of multi-planet systems, with possible effects on the history of our own solar system,” says Bohn. (The Astrophysical Journal Letters, 2020; doi: 10.3847 / 2041-8213 / aba27e)
Quelle: European Southern Observatory (ESO)
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