Since the 1990s, scientists have detected thousands of exoplanets orbiting distant stars, but the discovery of baby protoplanets embedded within stellar expanses of gas and dust has proven to be a challenge. An international team of astronomers has used a new technique to finally discover not one, but three infant planets around a newborn star—an incredible finding that’s affirming long-held assumptions about planet formation.
Normally, exoplanets are detected when they move in front of their host star, resulting in a brief dimming effect, or when their gravity causes a host star to jiggle ever so slightly. But these techniques don’t lend themselves very well to the study of protoplanetary disks—murky expanses filled with rocks, dust, and gas. This is a problem because scientists would very much like to detect protoplanets; the going theory is that planets form within these disks, but astronomers have never actually seen this process in action, nor have they ever detected an infant planet within these dusty incubators. But that’s now changed, thanks to two new papers published today in Astrophysical Journal Letters .
Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, two teams of astronomers have detected three infant planets around HD 163296, a young star located about 330 light-years from Earth. This star is twice the size of our own Sun, but at four million years old, it’s a mere one-thousandth the Sun’s age. To detect the new planets, the astronomers used a new technique that detects anomalous patterns of flowing gas within planet-forming disks.
The team, led by Richard Teague, an astronomer at the University of Michigan, found a pair of Jupiter-massed protoplanets located 7.4 billion miles (12 billion km) and 13 billion miles (21 million km) from the host star—that’s 80 and 140 times the distance from the Earth to the Sun (AU), respectively.
Independently, astronomer Christopher Pinte and his team from Monash University in Clayton, Australia, found a planet a bit further out , around 24 billion miles (39 billion km) from the host star, or 260 AU. All three planets were firmly embedded within HD 163296’s protoplanetary disk.