Astronomers have captured the first-ever image of a growing planet outside our solar system, nestled within a cleared gap of a multi-ringed disk of dust and gas. This groundbreaking discovery was made by a team led by University of Arizona astronomer Laird Close and Richelle van Capelleveen, a graduate student at Leiden Observatory in the Netherlands. Using advanced adaptive optics systems at the Magellan Telescope in Chile, the Large Binocular Telescope in Arizona, and the Very Large Telescope at the European Southern Observatory in Chile, the team unveiled their findings in The Astrophysical Journal Letters.
For years, scientists have speculated about the existence of planet-forming disks around young stars, which often display gaps hinting at the presence of nascent planets. However, until now, no definitive protoplanets had been observed within these dark rings. “Dozens of theory papers have been written about these observed disk gaps being caused by protoplanets, but no one’s ever found a definitive one until today,” said Close, emphasizing the significance of this discovery in resolving a longstanding scientific debate.
Unveiling the Mysteries of Protoplanetary Disks
Approximately 4.5 billion years ago, our solar system began as a similar disk of dust and gas. As material coalesced, the first protoplanets formed, a process still shrouded in mystery. To unravel these secrets, astronomers study planet-forming disks, or protoplanetary disks, in other systems. Close’s team utilized the MagAO-X adaptive optics system, which enhances image sharpness by compensating for atmospheric turbulence, to explore these disks.
The team’s focus was on detecting hydrogen alpha (H-alpha) emissions, a specific type of visible light emitted when hydrogen gas crashes onto a forming planet, creating hot plasma. “MagAO-X is specially designed to look for hydrogen gas falling onto young protoplanets, and that’s how we can detect them,” explained Close.
Discovering WISPIT 2b: A Rare Protoplanet
Using the Magellan Telescope and MagAO-X, the team examined WISPIT-2, a disk recently discovered by van Capelleveen. In H-alpha light, they identified a dot of light within the gap between two rings of the protoplanetary disk, marking the presence of a protoplanet. Additionally, they observed a second potential planet within the cavity between the star and the disk’s inner edge.
“Once we turned on the adaptive optics system, the planet jumped right out at us,” Close remarked, describing the discovery as one of the most significant in his career. The planet, named WISPIT 2b, is a rare example of a protoplanet actively accreting material. Its host star, WISPIT 2, is similar in mass to the sun. The inner planet candidate, CC1, is estimated to have about nine Jupiter masses, while WISPIT 2b has approximately five Jupiter masses.
“It’s a bit like what our own Jupiter and Saturn would have looked like when they were 5,000 times younger than they are now,” said Gabriel Weible, a graduate student involved in the research.
Implications and Future Research
This discovery has significant implications for our understanding of planetary formation. The detection of WISPIT 2b supports the hypothesis that protoplanets can indeed create gaps in protoplanetary disks. “Around WISPIT 2 you likely have two planets and four rings and four gaps. It’s an amazing system,” Close noted.
CC1 is believed to orbit at about 14-15 astronomical units (AU) from its star, comparable to the distance between Saturn and Uranus in our solar system. WISPIT-2b is farther out at about 56 AU, akin to the outer edge of the Kuiper Belt.
A parallel study led by van Capelleveen and the University of Galway identified the planet in the infrared spectrum and detailed the multi-ringed system using the VLT telescope’s SPHERE adaptive optics system. “To see planets in the fleeting time of their youth, astronomers have to find young disk systems, which are rare,” van Capelleveen explained.
This research was supported by the NASA eXoplanet Research Program, with MagAO-X developed through grants from the U.S. National Science Foundation and the Heising-Simons Foundation. As astronomers continue to explore these celestial phenomena, discoveries like WISPIT 2b provide invaluable insights into the early stages of planet formation, offering a glimpse into the processes that shaped our own solar system billions of years ago.
