Astronomers used the James Webb Space Telescope to investigate a stellar nursery full of baby stars in the Orion Nebula. The research helped reveal the impact of radiation from massive stars on planet formation.
The Orion Nebula is a huge complex of gas and dust that forms the building blocks of new stars. In fact, it is the closest star forming region to Earth. However, this star precursor material can also absorb light, acting as a shield for newborn, post-natal stars. This makes it difficult for scientists to see those baby stars from our vantage point on Earth. The light emitted by bodies is effectively hidden. Fortunately, the material is less effective at blocking low-energy, longer-wavelength light: infrared light.
This means that the powerful, infrared-sensitive JWST allows astronomers to peer through the clouds of the Orion Nebula even from nearly 1,400 light-years away. And the team’s new research focused on a disk of material called d203-506. This is a disk that is currently forming planets. After closer examination, the researchers found that the disk, called the protoplanetary disk, may not form some planets. They think this is due to the actions of other stars.
The present protoplanetary disk surrounds a small red dwarf star thought to be less than 1 million years old and to have at most 10% the mass of the Sun. This means that the star is relatively young and relatively cold. But in addition to being only lightly irradiated by its central star, d203-506 is also bombarded by intense, high-energy ultraviolet radiation from surrounding young massive stars.
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“Massive stars 10 times the size of the Sun are 100,000 times brighter than the Sun and therefore emit strong UV radiation into the disks around nearby sun-like stars,” said team leader and research scientist Olivier Berné. Institut de Recherche en Astrophysique et Planétologie told space.com. “This radiation heats the gas, which then escapes from the disk where planets are expected to form; we call this ‘photoevaporation.’ So their actions may suppress the formation of planets.”
Some stars find it harder to lose mass
The main result of the team’s research was the discovery that whatever planetary system emerges from the d203-506 disk, there will be no analogue to our solar system’s largest world, Jupiter.
This is because the intense burst of UV radiation would likely suppress the formation of such a gas giant.
“Thanks to infrared observations with JWST, we were able to measure the rate at which the gas escapes,” said Berné. “We found that in D203-506 the disk is losing about one Earth mass per year. That’s a huge mass loss!”
This research was necessary because, ironically, the massive stars that bombard protoplanetary disks with radiation do not always act in ways that suppress planet formation. “We think the solar system formed in an environment similar to Orion, so observing systems like d203-506 is a way to travel into the past,” Berné said.
However, this raises the question of why the solar system was able to form Jupiter while d203-506 could not.
“An important parameter is the mass of the star around which planets can form,” Berné said. said. “The star D203-506 has 5 to 10 times less mass than the Sun. Therefore, it has a weak gravitational field, which means its disk cannot resist photoevaporation well. A star like the Sun has a larger gravitational field, so It can better resist photoevaporation.”
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Protoplanetary disk d203-506 came to the attention of the team behind this discovery after being observed by the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile.
“It was a bit of a stroke of luck. This object was seen with Hubble, but it was very faint. But in some previous observations with ALMA, we saw that it was quite bright, so we zoomed in with ALMA. Our ALMA data was also very nice, so we thought we should observe it with JWST,” he said. Berne. “JWST produced many surprises, the biggest of which was how rich the spectra we obtained were.
“There is an incredible amount of information in the data; it has already been a year since we obtained it, but we have probably only used 10% of the useful information.”
The team’s research will be published in the March 1 issue of the journal Science.