Signs of two infant planets around young star detected

New York, Dec 13 (IANS) Astronomers believe they have found compelling evidence for two newborn planets, each about the size of Saturn, orbiting around a young star known as HD 163296.

These planets, which are not yet fully formed, revealed themselves by the dual imprint they left in both the dust and the gas portions of the star’s protoplanetary disk, the researchers said.

In studying HD 163296, the research team used Atacama Large Millimeter/submillimeter Array (ALMA) to trace, for the first time, the distribution of both the dust and the carbon monoxide (CO) gas components of the disk at roughly the same level of detail.

“Our new observations provide intriguing evidence that planets are indeed forming around this one young star,” said study lead author Andrea Isella, astronomer at Rice University in Houston, Texas, US.

HD 163296 is roughly five million years old and about twice the mass of the Sun. It is located approximately 400 light-years from Earth in the direction of the constellation Sagittarius.

The researchers found three distinct gaps in the star’s dust-filled protoplanetary disk.

Using ALMA’s ability to detect the faint millimeter-wavelength “glow” emitted by gas molecules, Isella and his team discovered that there was also an appreciable dip in the amount of carbon monoxide in the outer two dust gaps.

By seeing the same features in both the gas and the dust components of the disk, the astronomers believe they have found compelling evidence that there are two planets coalescing remarkably far from the central star.

The width and depth of the two carbon monoxide gaps suggest that each potential planet is roughly the same mass as Saturn, the astronomers said in a study published in the journal Physical Review Letters.

In the gap nearest to the star, the team found little to no difference in the concentration of CO gas compared to the surrounding dusty disk.

This means that the innermost gap could have been produced by something other than an emerging planet, the study said.