About 300 light years from Earth is TYC 8998-760-1, a star that resembles our own sun, like a twin, but was born about four and a half billion years later. In May, a team of astronomers studying the sun-like star discovered that it was not alone - a giant gas planet kept it in company on its journey through the cosmos. They called it TYC 8998-760-1, as required by the convention.
Now, just two months later, the same team has discovered Another Planet, even farther from the star, called TYC 8998-760-1 c.
The discovery, published in the Astrophysical Journal Letters on Wednesday, is significant for planet hunters: it is the first time that several planets have been found directly mapped orbit a star similar to our sun.
"Our team was able to take the first picture of two gas giant companions orbiting a young solar analog," said Maddalena Reggiani, astronomer at the KU Leuven in Belgium and co-author of the study.
What does this mean for everyday skywatchers?
First of all, it is difficult to map exoplanets directly. Most of these distant worlds are discovered indirectly. Astronomers do not see the planet in visible light, but they can recognize it by its effects on bright stars. Some telescopes like NASA's TESSLook for dips in the brightness of the stars, which indicates that a planet has crossed the field of view. Other planetary hunters are looking for significant changes in the speed of stars caused by the gravitational effect of an invisible world. Both methods have helped astronomers find a huge amount of exoplanets.
However, there are rare cases where telescopes can See the planets directly. This is how the planets around TYC 8998-760-1 were discovered. It is difficult to image planets directly because they do not emit much light. The closer they are to their home sun, the more they hide the sun in the sky. With the Very Large Telescope in the Chilean Atacama Desert and the attached SPHERE instrument, planetary hunters can block the light - and discover nearby planets.
So TYC 8998-760-1 c was found.
It is not the first time that astronomers have seen several planets orbiting a star. This award goes to HR 8799. Researchers using the WM Keck Observatory and the Gemini Observatory in Mauna Kea, Hawaii, discovered three planets in orbit around HR 8799 in 2008. But HR 8799 is a strange kind of star that lacks heavy metals - it's nothing like our sun.
However, TYC 8998-760-1 is like our sun. It resembles a very (very) young version of our own sun, and the two planets resemble oversized versions of our own gas giants Jupiter and Saturn.
"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," said Alexander Bohn, astronomer at Leiden University in the Netherlands, who led the study, in a statement.
The next planet discovered in May is approximately 14 times as massive as Jupiter, while TYC 8998-760-1 c is approximately six times as massive. But the planets are much further away from their host star. The distance to planet b is approximately 160 au or astronomical units - which makes it 160 times larger than the distance between the earth and the sun. Planet c is twice as far away.
The former planet Pluto on the edge of our solar system is only 40 au.
The European Southern Observatory, which operates the Very Large Telescope, is constructing a brand new eye for the sky with the imaginative name "Extremely Large Telescope". Seriously. The new telescope should go online sometime in 2025 and offer astronomers an even clearer insight into TYC 8998-760-1. And when other planets lurk invisibly in the system, the ELT can help them discover them.
There are also NASA's infinitely delayed James Webb telescopeThis could examine the system at different wavelengths and help determine the atmosphere types of the giant exoplanets.
