Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have spotted a circumplanetary disk around a still-forming gaseous exoplanet called PDS 70c.
Source: Sci News
“For the first time, we can conclusively see the telltale signs of a circumplanetary disk, which helps to support many of the current theories of planet formation,” said Dr. Andrea Isella, an astronomer at Rice University.
PDS 70, also known as V1032 Cen, is a K7-type star at a distance of about 370 light-years.
The star is only 5.4 million years old, slightly smaller and less massive than our Sun, and it hosts at least two young gas giants.
The planets are 5-10 times larger than Jupiter, and the innermost, PDS 70b, orbits about 1.8 billion miles from the star, roughly the distance from the Sun to Uranus. PDS 70c is a billion miles further out, in an orbit about the size of Neptune’s.
“Planets form from disks of gas and dust around newly-forming stars, and if a planet is large enough, it can form its own disk as it gathers material in its orbit around the star,” Dr. Isella said.
“Jupiter and its moons are a little planetary system within our Solar System, for example, and it’s believed Jupiter’s moons formed from a circumplanetary disk when Jupiter was very young.”
But most models of planet formation show that circumplanetary disks disappear within about 10 million years, which means circumplanetary disks haven’t existed in the Solar System for more than 4 billion years.
To look for them elsewhere and gather observational evidence to test theories of planet formation, Dr. Isella and colleagues search for very young star systems where they can directly observe disks and the planets still forming inside them.
In the new study, the astronomers analyzed observations made by ALMA in 2017.
“There are a handful of candidate planets that have been detected in disks, but this is a very new field, and they are all still debated,” Dr. Isella said.
“PDS 70b and c are among the most robust because there have been independent observations with different instruments and techniques.”
The findings appear in the Astrophysical Journal Letters.