3 baby alien planets discovered around newborn stars

Artist illustration of protoplanets forming around a young star. Credit: S. Dagnello; NSF/NRAO/AUI

Three exoplanets are in the process of being born around a young star that is not too far from the sun, two new studies report.

That star is the 4-million-year-old HD 163296, which is located about 330 light years from our solar system, in the direction of the constellation Sagittarius.

Previous observations of HD 163296 by the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile turned out to be a “protoplanetary disk of gas and dust the star they orbit. This disc features two dark holes, which astronomers believe were carved by newly formed planets. [See: 2 Births Planets Can Form Around a Distant Young Star]

The two new studies give strong evidence for the existence of the two alleged alien worlds, as well as a third. All three are Jupiter-like gas giants, and they orbit at distances of 80 AU, 140 AU and 260 AU, researchers said. (An AU, short for “astronomical unit” is the average Earth-sun distance, about 93 million miles, or 150 kilometers.)

Both teams looked to ALMA data. But, instead of studying the holes in the disk, they used a new strategy: analyze the movement of carbon monoxide (CO) gas. CO and other gases tend to move in a predictable way in protoplanetary disks, unless they run into heavy obstacles.

“It would be a relatively solid object, such as a planet, to create localized disturbances in this otherwise orderly movement,” Christophe Pinte of Monash University in Australia, lead author of one of the two new papers, said in a statement. “Our new technique applies this principle to help us understand how planets form.”

Pinte team determined that the outer planet in the HD 163296 system. The other team, led by Richard Teague of the University of Michigan, used the same methods to spot the other two worlds.

The combining of the ALMA CO observations with computer modeling work, the researchers were able to estimate the masses of the young exoplanets. All three of them seem to be gas giants, with masses not too different from that of Jupiter, the researchers said.

Astronomers have discovered more than 3,700 confirmed exoplanets to date. The vast majority have been detected using one of two strategies — the “transit-method”, that the comments of the small brightness dips caused when a world crosses its star’s face; or the “radial-velocity method”, which picks up the small movements in a star caused by the gravitational pull of an orbiting planet.

However, none of these techniques is suitable for the finding of new-born worlds in protoplanetary disks. So the two new studies could open doors, researchers said.

“This completely new approach could discover in some of the youngest planets in our galaxy, all thanks to the high-resolution images from ALMA,” Teague said in the same statement.

The two studies were published online today (13 June) in the Astrophysical Journal Letters.

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