If you’ve ever tried to take a group photo, you know it can be tricky to get everyone lined up nicely in the frame. Now, imagine how hard it is to snap a cosmic family photo that includes multiple planets orbiting a Sunlike star some 300 light years from Earth.
An international team of astronomers has accomplished this feat for the first time ever, according to a study published on Wednesday in The Astrophysical Journal Letters. The stunning snapshot reveals two huge worlds orbiting a star called TYC 8998-760-1, and was taken by European Southern Observatory's Very Large Telescope in Chile.
“Even though tens of directly imaged companions have been discovered in the past decades, the number of directly confirmed multiplanet systems is still small,” said the team in the study, which was led by Alexander Bohn, a PhD student at Leiden University in the Netherlands.
“TYC 8998-760-1 is the first directly imaged multiplanet system that is detected around a young, solar analog,” the researchers added.
While astronomers snap pictures of stars all the time, any planets in these systems are normally too dim to show up in images. For this reason, the vast majority of exoplanets, which are worlds outside our solar system, are discovered when they pass in front of their stars from our perspective on Earth, allowing scientists to detect a dip in the brightness of the star’s light.
Though more than 4,000 exoplanets have been detected, only about two dozen of those bodies have been directly imaged from Earth. Capturing multiple planets in one shot is even rarer; astronomers have only taken two images that show more than one exoplanet, and neither of those systems contained a star similar to the Sun.
TYC 8998-760-1, in contrast, is about the same mass as the Sun, though it is a baby compared to our middle-aged star. While the Sun has been around for at least 4.5 billion years, TYC 8998-760-1 and its planets are a wee 17 million years old.
The young age of the system is part of the reason that Bohn and his colleagues were able to capture the spectacular new shot. Like their host star, the two giant planets in the picture are infants, which means they are still hot out of the cosmic oven compared to planets in our own solar system that have gradually cooled down. As a result, the two planets glow with infrared light, making it easier for VLT to image them.
The unprecedented snapshot was also made possible by the sheer girth of these colossal gas planets. Jupiter may be the titan of our solar system, but it is 14 times smaller than the inner exoplanet orbiting TYC 8998-760-1, and six times smaller than the more distant giant planet.
The two enormous planets also orbit their star at more extreme distances than planets in our solar system orbit the Sun. The inner exoplanet is located about 32 times as far as Jupiter is from the Sun, and the outer exoplanet is about twice that distance from its star. Future observations may reveal whether the planets formed at those farflung positions or if they have migrated out into the stellar wilds over the past few million years.
"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," said Bohn in a statement.
“The possibility that future instruments, such as those available on the [ESO’s Extremely Large Telescope], 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."