Astronomers have long known that planets are born in protoplanetary disks – rings of dust and gas surrounding young, newborn stars. However, although hundreds of such disks have been spotted throughout the universe, observations of actual planetary birth and formation are quite difficult due to technological limitations. Now, a team of astronomers from the Center for Astrophysics | Harvard & Smithsonian has developed a novel method to detect such elusive newborn planets through which they spotted a young planet located 518 light years away.
“Directly detecting young planets is very challenging and has so far only been successful in one or two cases,” said study lead author Feng Long, a postdoctoral fellow at the Center for Astrophysics. “The planets are always too faint for us to see because they’re embedded in thick layers of gas and dust.”
“In the past few years, we’ve seen many structures pop up on disks that we think are caused by a planet’s presence, but it could be caused by something else, too. We need new techniques to look at and support that a planet is there.”
Together with her colleagues, Dr. Long re-examined a protoplanetary disk called LkCa 15, located 518 light years away from the Earth, in the Taurus constellation. By using high-resolution data collected from the ALMA Observatory, the scientists discovered a dusty ring with two separate, bright bunches of material orbiting within it approximately 42 astronomical units from the star (about 42 times the distance between the Earth and the Sun). This material consisted of a small clump and a larger arc separated by 120 degrees. According to Dr. Long, the size, location, and structure of these materials suggested the presence of a newborn planet.
“This arc and clump are separated by about 120 degrees. That degree of separation doesn’t just happen — it’s important mathematically,” she explained. “We’re seeing that this material is not just floating around freely, it’s stable and has a preference where it wants to be located based on physics and the objects involved.”
To detect this planet, the scientists investigated positions in space known as Lagrange points, where two bodies in motion, such as a star and its orbiting planet, produce enhanced areas of attraction around them where matter can accumulate. In this case, the arc and clump of material detected were located at the L4 and L5 Lagrange points. Hidden 60 degrees between them was a small, young planet causing the accumulation of dust at these points. The analysis revealed that the planet is roughly the size of Saturn or Neptune, and was formed between one and three million years ago – a young age when it comes to planets.
Although imaging this small, newborn planet may not be possible in the near future due to technological limitations, the researchers hope that further ALMA observations of LkCa 15 can provide additional evidence supporting this planetary discovery, and that this new approach of detecting planets – with material accumulating at Lagrange points – could be used by other astronomers.
“I do hope this method can be widely adopted in the future. The only caveat is that this requires very deep data as the signal is weak,” Dr. Long concluded.
The study is published in the Astrophysical Journal Letters.
By Andrei Ionescu, Earth.com Staff Writer