A team of astronomers has detected for the first time a growing planet outside our solar system, embedded in a cleared gap of a multi-ringed disk of dust and gas.
The team, led by University of Arizona astronomer Laird Close and Richelle van Capelleveen, an astronomy graduate student at Leiden Observatory in the Netherlands, discovered the unique exoplanet using the University of arizona’s magao-X extreme adaptive optics system at the Magellan Telescope in Chile, the U of A’s Large Binocular telescope in Arizona, and the Very Large Telescope at the European Southern Observatory in Chile.
Their results are published in The Astrophysical Journal Letters.
For years, astronomers have observed several dozen planet-forming disks of gas and dust surrounding young stars. Many of these disks display gaps in their rings, hinting at the possibility that they are being “plowed” by nearby nascent planets, or protoplanets, like lanes being cleared by a snowplow.
Yet, only about three actual young growing protoplanets have been discovered to date, all in the cavities between a host star and the inner edge of its adjacent protoplanetary disk. Until this revelation, no protoplanets had been seen in the conspicuous disk gaps-which appear as 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,” says Close, professor of astronomy at the University of Arizona.
He calls the discovery a “big deal,” because the absence of planet discoveries in places were they shoudl be has prompted many in the scientific community to invoke alternative explanations for the ring-and-gap pattern found in many protoplanetary disks.
“It’s been a point of tension, actually, in the literature and in astronomy in general, that we have these really dark gaps, but we cannot detect the faint exoplanets in them,” he says.
“Many have doubted that protoplanets can make these gaps, but now we know that in fact, they can.”
4.5 billion years ago, our solar system began as just such a disk.As dust coalesced into clumps,sucking up gas around them,the first protoplanets began to form. How exactly this process unfolded,however,is still largely a mystery. To find answers, astronomers have looked to other planetary systems that are still in their infancy, known as planet-forming disks, or protoplanetary disks.
Close’s team took advantage of an adaptive optics system, one of the most formidable of its kind in the world, developed and built by Close, Jared Males, and their students.
Astronomers Capture First Image of a Growing Protoplanet with Rings
Astronomers have, for the first time, directly imaged a young planet still in the process of formation, complete with a surrounding ring system. The groundbreaking discovery, detailed in two recently published papers, offers a glimpse into the early stages of planet formation, resembling what Jupiter and Saturn may have looked like billions of years ago.
The protoplanet, designated WISPIT 2b, orbits the star WISPIT 2, a sun-like star of comparable mass located within the WISPIT (Warm, young, and Isolated Planet-forming disk) survey. The observations were made possible by the University of Arizona’s 8.4-meter Large Binocular Telescope (LBT) on mount Graham, utilizing the MagAO-X adaptive optics system, and the European Southern Observatory’s 8-meter Very Large Telescope (VLT) in Chile.
“After combining two hours’ worth of images, it just popped out,” said Dr. Jared Close, lead author of one of the studies and a professor at Arizona State University, describing the moment WISPIT 2b became visible.
The system appears to host at least two planets. The outer planet, WISPIT 2b, is estimated to be approximately five times the mass of Jupiter. An inner planet candidate, CC1, is even more massive, weighing in at around nine Jupiter masses. These mass estimations were derived from thermal infrared light observations. The team also identified evidence of four rings and four gaps within the surrounding disk of material.
“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,” explained Gabriel Weible, a university of Arizona astronomy graduate student involved in the research.
The planets in the WISPIT-2 system are significantly more massive and more widely spaced than the gas giants in our solar system.However, astronomers believe the overall appearance would be recognizable to an “alien astronomer” observing a young solar system 4.5 billion years ago.
The MagAO-X system played a crucial role in the discovery. “Our MagAO-X adaptive optics system is optimized like no other to work well at the H-alpha wavelength, so you can separate the radiant starlight from the faint protoplanet,” Close explained.
CC1 orbits at approximately 14-15 astronomical units (AU) – halfway between Saturn and Uranus in our solar system. WISPIT 2b is much further out, at around 56 AU, placing it beyond Neptune and near the outer edge of the Kuiper Belt.
A parallel study, led by Dr. Christian van Capelleveen of the University of Galway, confirmed the planet’s presence using infrared light and detailed the multi-ringed system with the VLT’s SPHERE adaptive optics system. Van Capelleveen emphasized the rarity of observing protoplanets directly. “To see planets in the fleeting time of their youth, astronomers have to find young disk systems, which are rare, because that’s the one time that they really are brighter and so detectable. if the WISPIT-2 system was the age of our solar system and we used the same technology to look at it, we’d see nothing. Everything would be too cold and too dark.”
This research highlights the importance of studying young planetary systems to understand the processes that lead to the formation of planets like those in our own solar system.
The research was supported by grants from NASA’s eXoplanet Research Program, the US National Science Foundation, and the Heising-simons Foundation.
Sources:
* University of Arizona News: https://news.arizona.edu/news/growing-baby-planet-photographed-first-time-ring-darkness