Using the Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the NASA/ESA/CSA James Webb Space Telescope, astronomers have discovered six new free-floating planetary-mass members of NGC 1333 with estimated masses between 5 and 15 times the mass of Jupiter. One of these objects, at 5 Jupiter masses (about 1,600 Earths), is a good candidate to be the lowest mass object known to have a dusty circumplanetary disk.
At an estimated mass of 5 Jupiter masses, NIRISS-NGC1333-5 (also known as NN5) is a good candidate to be the lowest-mass object found in NGC 1333 thus far and the lowest-mass object with a disk in any region identified to date. Image credit: Langeveld et al., doi: 10.3847/1538-3881/ad6f0c.
NGC 1333 is a star-forming cluster located some 1,000 light-years away in the northern constellation of Perseus.
Also known as Ced 16 and LBN 741, the cluster was first discovered by the German astronomer Eduard Schönfeld in 1855.
Only 1-3 million years old, NGC 1333 hosts about half as many brown dwarfs as stars, a higher proportion than seen before.
“We are probing the very limits of the star forming process,” said Johns Hopkins University astrophysicist Adam Langeveld.
“If you have an object that looks like a young Jupiter, is it possible that it could have become a star under the right conditions? This is important context for understanding both star and planet formation.”
Dr. Langeveld and his colleagues carried out an extremely deep spectroscopic survey of NGC 1333 using Webb’s NIRISS instrument.
The observations revealed 19 known brown dwarfs and 6 free-floating planetary-mass objects between 5 and 10 times more massive than Jupiter.
That means they are among the lowest-mass objects ever found to have grown from a process that would generally produce stars and brown dwarfs, objects straddling the boundary between stars and planets that never ignite hydrogen fusion and fade over time.
“We used Webb’s unprecedented sensitivity at infrared wavelengths to search for the faintest members of a young star cluster, seeking to address a fundamental question in astronomy: how light an object can form like a star?” said Johns Hopkins University astrophysicist Ray Jayawardhana.
“It turns out the smallest free-floating objects that form like stars overlap in mass with giant exoplanets circling nearby stars.”
The Webb observations revealed no objects lower than five Jupiter masses despite possessing sufficient sensitivity to detect such bodies.
That’s a strong indication that any stellar objects lighter than this threshold are more likely to form the way planets do.
“Our observations confirm that nature produces planetary mass objects in at least two different ways — from the contraction of a cloud of gas and dust, the way stars form, and in disks of gas and dust around young stars, as Jupiter in our own Solar System did,” Dr. Jayawardhana said.
The most intriguing of the planetary-mass objects, NIRISS-NGC1333-5, is also the lightest, having an estimated mass of 5 Jupiters.
“The presence of a dusty disk means the object almost certainly formed like a star, as space dust generally spins around a central object in the early stages of star formation,” Dr. Langeveld said.
“Disks are also a prerequisite for the formation of planets, suggesting the observations may also have important implications for potential mini planets.”
“Those tiny objects with masses comparable to giant planets may themselves be able to form their own planets,” said Dr. Aleks Scholz, an astrophysicist at the University of St Andrews.
“This might be a nursery of a miniature planetary system, on a scale much smaller than our Solar System.”
The astronomers also discovered a new brown dwarf with a planetary-mass companion, a rare finding that challenges theories of how binary systems form.
“It’s likely that such a pair formed the way binary star systems do, from a cloud fragmenting as it contracted,” Dr. Jayawardhana said.
“The diversity of systems that nature has produced is remarkable and pushes us to refine our models of star and planet formation.”
The findings will be published in the Astronomical Journal.
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Adam B. Langeveld et al. 2024. The JWST/NIRISS Deep Spectroscopic Survey for Young Brown Dwarfs and Free-Floating Planets. AJ, in press; doi: 10.3847/1538-3881/ad6f0c
Source : Breaking Science News