Scientists directly observe growth of infant exoplanet

Observation will give scientists new insights into the early stages of planet formation.

For the first time ever, scientists have observed a baby exoplanet in the process of growing by accreting material from the disk surrounding the star it orbits.

Using adaptive optics on the 6.5-meter Magellan Clay Telescope in Chile, a team of astronomers led by Kevin Wagner of the University of Arizona, Amherst College, NExSS and Earths in Other Solar Systems studied the 10-million-year old parent star, an orange dwarf known as PDS 70, located 370 light years from Earth.

Unlike most planets in the process of forming, which can be imaged only indirectly as gaps in the circumstellar disks surrounding young stars, PDS 70b has been seen directly as it accretes material from the disk surrounding its star.

“These disks around young stars are the birthplaces of planets, but so far, only a handful of observations have detected hints of baby planets in them. The problem is that until now, most of these planet candidates could just have been features in the disk,” said Miriam Keppler of the Max Planck Institute for Astronomy in Heidelberg, Germany, and leader of the group that initially discovered PDS 70b.

The researchers observed the system in hydrogen alpha and similar wavelengths on two nights last May. They detected hydrogen alpha emissions at the site of the planet, indicating hot hydrogen gas is falling onto it, a clear sign that it is still accreting material.

Even though it is a baby planet still in the process of forming, PDS 70b is already larger than Jupiter. Scientists estimate it has completed 90 percent of its growth and that it likely accreted material at a much faster rate in its early years than it is doing so now.

PDS 70b’s surface temperature is estimated to be approximately 1,382 degrees Fahrenheit (1,000 degrees Celsius), and its atmosphere is thought to be cloudy.

Being able to observe the process of a planet growing by gathering materials from a star’s circumstellar disk will give scientists new insight into the planet formation process.

The research team’s findings have been published in The Astrophysical Journal Letters.

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