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Multiplanet system around sunlike star photographed for 1st time ever

For the first time ever, astronomers have directly imaged multiple planets orbiting a sunlike star.

The European Southern Observatory's Very Large Telescope (VLT) in Chile photographed two giant planets circling TYC 8998-760-1, a very young analogue of our own sun that lies about 300 light-years from Earth, a new study reports.

"This discovery is a snapshot of an environment that is very similar to our solar system, but at a much earlier stage of its evolution," study lead author Alexander Bohn, a doctoral student at Leiden University in the Netherlands, said in a statement. 

Related: The strangest alien planets (gallery)

The two giant planets in the TYC 8998-760-1 system are visible as two bright dots in the center (TYC 8998-760-1b) and bottom right (TYC 8998-760-1c) of the frame, noted by arrows. Other bright dots, which are background stars, are visible in the image as well. By taking different images at different times, the team was able to distinguish the planets from the background stars. The image was captured by blocking the light from the young, sunlike star (top-left of center) using a coronagraph, which allows for the fainter planets to be detected. The bright and dark seen on the star’s image are optical artifacts.

The two giant planets in the TYC 8998-760-1 system are visible as two bright dots in the center (TYC 8998-760-1b) and bottom right (TYC 8998-760-1c) of the frame, noted by arrows. Other bright dots, which are background stars, are visible in the image as well. By taking different images at different times, the team was able to distinguish the planets from the background stars. The image was captured by blocking the light from the young, sunlike star (top-left of center) using a coronagraph, which allows for the fainter planets to be detected. The bright and dark seen on the star’s image are optical artifacts.  (Image credit: ESO/Bohn et al.)

Before this historic cosmic portrait, only two multiplanet systems had ever been directly imaged, and neither of them features a sunlike star, study team members said. And snapping a photo of even a single exoplanet remains a rare achievement.

"Even though astronomers have indirectly detected thousands of planets in our galaxy, only a tiny fraction of these exoplanets have been directly imaged," study co-author Matthew Kenworthy, an associate professor at Leiden University, said in the same statement.

Bohn, Kenworthy and their colleagues studied the 17-million-year-old star TYC 8998-760-1 with the VLT's Spectro-Polarimetric High-contrast Exoplanet Research instrument, or SPHERE for short. SPHERE uses a device called a coronagraph to block a star's blinding light, allowing astronomers to see and study orbiting planets that would otherwise be lost in the glare.

The newly reported SPHERE imagery revealed two planets in the system, TYC 8998-760-1b and TYC 8998-760-1c. Astronomers already knew about TYC 8998-760-1b — a team led by Bohn announced its discovery late last year — but TYC 8998-760-1c is a newfound world.

The two planets are huge and farflung. TYC 8998-760-1b is about 14 times more massive than Jupiter and orbits at an average distance of 160 astronomical units (AU), and TYC 8998-760-1c is six times heftier than Jupiter and lies about 320 AU from the host star. (One AU is the average Earth-sun distance — about 93 million miles, or 150 million kilometers. For comparison: Jupiter and Saturn orbit our sun at just 5 AU and 10 AU, respectively.)

It's unclear whether the two worlds in TYC 8998-760-1 formed at their present locations or were pushed out there somehow. Further observations, including those made by huge future observatories such as the European Extremely Large Telescope (ELT), could help to solve that mystery, study team members said.

Other questions remain about the TYC 8998-760-1 system as well. For example, do the two gas giants have company? Might several rocky planets circle relatively close to the star, as they do in our solar system? 

"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 multiplanet systems, with potential implications for the history of our own solar system," Bohn said. 

The new study was published online today (July 22) in The Astrophysical Journal Letters.

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook. 

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