Planets are known to form from protoplanetary discs, which are dust rings that surround young newly born stars. Astronomers have discovered hundreds of such discs throughout the universe, but they have only rarely been able to observe planetary formation and birth. The Harvard & Smithsonian Centre for Astrophysics has now developed a new method for detecting these “newborn planets.”
“Detecting young planets directly is extremely difficult and has only been successful in one or two cases so far.” “The planets are always too faint for us to see because they’re embedded in thick layers of gas and dust,” said Feng Long, a postdoctoral fellow at the Center for Astrophysics and the study’s lead author, in a press release. Long is the study’s first author, and it was published in The Astrophysical Journal Letters.
Instead, scientists must look for clues that will lead them to believe that a planet is forming beneath the dust. “In recent years, we’ve seen many structures appear on discs that we believe are caused by the presence of a planet, but they could also be caused by something else.” “We need new techniques to look at and support the existence of a planet,” Wong added.
Long began her investigation by re-examining LkCa 15, a protoplanetary disc 518 light years away from Earth in the direction of the Taurus constellation. Previously, scientists used ALMA Observatory observations to report evidence of planet formation in the disc.
Long discovered two previously unknown faint features in high-resolution ALMA data of LkCa 15—two separate and bright bunches of material orbiting within the disc about 42 astronomical units away from the star at the centre. These bunches had the appearance of a small clump and a larger arc.
“This arc and clump are about 120 degrees apart,” she says. “That degree of separation doesn’t just happen; it’s mathematically significant.” “We’re seeing that this material is stable and has a preference for where it wants to be located based on physics and the objects involved,” Long explained.
The arc and clump of material in the disc are located at the L4 and L5 Lagrange points. A small planet about 60 degrees between them is causing dust accumulation. Lagrange points are locations in space where two moving bodies, such as a star and an orbiting planet, create areas of enhanced attraction where matter can accumulate. The observations reveal a planet roughly the size of Neptune that is one to three million years old, which is relatively young in planetary terms.
However, due to technological limitations, direct imaging of the small “baby” planet is not possible, but Long believes that additional ALMA observations of LkCa 15 will provide additional evidence to support her discovery. Long also hopes that astronomers will use the new method for detecting young planets by looking for material accumulating at Lagrange points in the future.