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A global team of researchers, with affiliations to the University of Michigan, has observed the earliest instances of planets starting to form around a star beyond our solar system.
This discovery represents the first occasion when a planetary system has been recognized at such an early phase of development, providing insight into the history of our own solar system.
This nascent planetary system is coming together around the young star HOPS-315, located approximately 1,300 light years from Earth. Around these youthful stars, astronomers frequently observe disks of gas and dust referred to as protoplanetary disks, which serve as the birthplaces of new planets.
Utilizing the JWST space telescope alongside the Atacama Large Millimeter Array (ALMA) in Chile, the scientists noted indicators of dust and gas coalescing to form solid materials. These materials subsequently merge, initially creating planet-like seeds termed “planetesimals,” which eventually evolve into full-fledged planets over time.
“This process has never been captured before in a protoplanetary disk—or anywhere beyond our solar system,” remarked Edwin Bergin, co-author of the new research and a professor of astronomy at U-M.
While researchers have previously observed disks containing young planets, they have not witnessed the actual genesis of planets. However, they had a clear idea of what to seek to finally document the initial stages of a planet’s existence.
“We’ve always understood that the first solid components of planets, or planetesimals, would have to form earlier, at previous stages,” stated Melissa McClure, lead author of the paper and an assistant professor at Leiden University in the Netherlands. McClure completed her doctorate at U-M in 2015.
Now, researchers from eight institutions across five nations have combined the capabilities of JWST and ALMA to capture “an image of the infant solar system,” said co-author Merel van ‘t Hoff, who initiated the project as a postdoctoral researcher at U-M and is currently an assistant professor at Purdue University.
“This system is one of the finest we know to analyze some of the processes that took place in our solar system,” she observed regarding the HOPS-315 system.
In our solar system, the very first solid substances to condense near Earth’s current location around the sun are found embedded within ancient meteorites. Astronomers utilize age-dating techniques on these primordial rocks to ascertain when the formation clock for our solar system began. Such meteorites are filled with crystalline minerals that contain silicon monoxide, or SiO, and can condense at the extremely high temperatures found in young planetary disks.
As time passes, these newly formed solids merge, planting the seeds for planet formation as they accumulate both size and mass. The initial kilometer-sized planetesimals in the solar system, which eventually became the cores of Earth and Jupiter, emerged shortly following the condensation of these crystalline minerals.
In this recent discovery, astronomers have identified signs of these hot minerals beginning to solidify in the disk surrounding HOPS-315. Their findings indicate that SiO exists around the young star in both its gaseous form and within crystalline minerals, implying it is only starting to turn solid.
“We’re truly observing these minerals in the same vicinity within this extrasolar system as where we encounter them in asteroids in the Solar System,” states co-author Logan Francis, a postdoctoral researcher at Leiden University.
Due to this, the disk of HOPS-315 serves as an excellent model for exploring our cosmic past. It also grants astronomers a fresh opportunity to investigate early planet formation, acting as a representative for nascent solar systems throughout the galaxy.
The minerals were initially identified with the JWST, a collaborative project between NASA, the European Space Agency, and the Canadian Space Agency. To determine the exact origin of the signals, the team scrutinized the system using ALMA, an international observatory located in Chile’s Atacama Desert, managed by the National Radio Astronomy Observatory, the European Southern Observatory, and the National Astronomical Observatory of Japan.
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