Astronomers Devise a New Strategy For Discovering Infant Planets Around Young Stars

Saturday, 16 June 2018 - 4:40PM
Space
Astronomy
Saturday, 16 June 2018 - 4:40PM
Astronomers Devise a New Strategy For Discovering Infant Planets Around Young Stars
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NRAO/AUI/NSF; S. Dagnello
As it becomes more common to discover exoplanets in distant (or nearby) solar systems, we're starting to see more variety in the weird planets we're coming across.

And while that can teach us a lot about what sorts of planets can be out there, they teach us very little about how these planets form. Finding baby planets, or "protoplanets", isn't easy because young planets are usually found in young solar systems with young stars, and current methods for tracking down exoplanets don't work as well with young stars (more on that in a bit). 

So it's impressive that a team of astronomers has successfully developed a new planet-hunting strategy that's allowed them to pinpoint a young star with three protoplanets orbiting around it. Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, the researchers identified the star HD 163296, about 330 lightyears away, with the soon-to-be planets forming in its "protoplanetary disk".



When a star first forms, things are messy - the leftover materials used to form the star still linger around it, forming a protoplanetary disk which will, over time, split apart and form the planets in new solar system. Since most exoplanets are found using the "transit" method, by looking for dips in a star's brightness which suggest a planet is passing in front of it, an amorphous disk muddying up the solar system can make this method impossible.

What the researchers ultimately did was look at gases inside the disk, rather than dips in the brightness of the star. By focusing in on trace signals of carbon monoxide (which ALMA was well suited for), they could make use of the Doppler effect to determine whether gas was moving toward or away from Earth, and they could pick up disturbances in the gas which matched up with how a planet would be moving through the disk.

There were two teams here, with one led by Richard Teague of the University of Michigan who found two Jupiter-mass protoplanets in the HD163296 solar system, and a second team led by Christopher Pinte Monash University in Australia who found a third protoplanet on the edges of the solar system.

The star itself is two times the size of our sun, but only a thousandth of its age at a young four million years. Our sun is about 4.6 billion years old, so it's no child, but it's still got a lot of life left before it explodes (although it's too small to ever go supernova).
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