Ann Arbor Times

An international collaboration, including the University of Michigan, has identified six likely rogue worlds—objects with planet-like masses but not bound to any star’s gravity—using the James Webb Space Telescope (JWST). This discovery includes the lightest rogue planet candidate ever found with a dusty disk around it. These objects provide new evidence that cosmic processes responsible for star formation may also create objects slightly larger than Jupiter.

“We are probing the very limits of the star forming process,” said lead author Adam Langeveld, an astrophysicist at Johns Hopkins University. “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.”

The findings come from JWST’s deepest survey of NGC1333, a young nebula about 1,000 light-years away in the Perseus constellation. A new image from this survey was released today by the European Space Agency. The survey's results will be published in The Astronomical Journal.

“The take-home message here is that the JWST and, in particular, the NIRISS instrument is a great tool to find the very lowest mass objects in star clusters,” said Michael Meyer, professor and chair of U-M Department of Astronomy. He noted that one project he helped champion became NIRISS—the Near Infrared Imager and Slitless Spectrograph.

Infrared light has longer wavelengths than visible light and can travel through clouds of gas and dust relatively unperturbed. Instruments capable of detecting IR light are thus useful for observing areas where stars form.

“The JWST is the best IR telescope in space and it will be the very best facility for this type of work for years to come,” Meyer said. “We’ve been working on it for more than 25 years and it exceeded expectations.”

Matthew de Furio, now a postdoctoral researcher at the University of Texas, also contributed to this project as a doctoral student at U-M.

The data suggest these discovered worlds are gas giants 5 to 10 times more massive than Jupiter. They are among the lowest-mass objects formed from processes generally producing stars and brown dwarfs—objects straddling between stars and planets without igniting hydrogen fusion.

“We used Webb’s unprecedented sensitivity at infrared wavelengths to search for faint members of a young star cluster,” said Johns Hopkins Provost Ray Jayawardhana. “It turns out the smallest free-floating objects that form like stars overlap in mass with giant exoplanets circling nearby stars.”

The telescope detected no objects lighter than five Jupiter masses despite having sufficient sensitivity to do so. This indicates stellar objects lighter than this threshold likely form similarly to planets.

“Our observations confirm that nature produces planetary mass objects in at least two different ways—from gas cloud contraction like stars or within disks around young stars,” Jayawardhana explained.

One intriguing object is estimated at five Jupiters' mass—about 1,600 Earths—and has a dusty disk suggesting it formed like a star since space dust typically spins around central bodies during early stages of formation.

“Those tiny objects with masses comparable to giant planets may themselves be able to form their own planets,” said co-author Aleks Scholz from St Andrews University. “This might be a nursery of miniature planetary systems.”

Using NIRISS on JWST, astronomers measured infrared spectra across observed portions of NGC1333's cluster and reanalyzed 19 known brown dwarfs while discovering another brown dwarf with a rare planetary-mass companion challenging binary system formation theories.

“It’s likely such pairs formed like binary star systems do—from fragmenting clouds during contraction,” Jayawardhana stated. “Nature's diversity pushes us towards refining our models.”

Rogue worlds may originate from collapsing molecular clouds lacking nuclear fusion capacity or from coalescing gas/dust within disks ejected due to gravitational interactions with other bodies.

These free-floating entities blur celestial classifications due overlapping masses with gas giants/brown dwarfs yet account for about 10% within targeted clusters per new JWST data despite being rare galaxy-wide occurrences.

In upcoming months researchers plan atmospheric studies comparing faint object profiles against heavier counterparts alongside exploring potential mini-planetary system formations resembling those orbiting Jupiter/Saturn using further awarded JWST time focusing on similar dusty-disked entities.

Other authors include Koraljka Mužić & Daniel Capela (Universidade de Lisboa), Loïc Albert/René Doyon/David Lafrèniere (Université de Montréal), Laura Flagg (Johns Hopkins) & Doug Johnstone (Herzberg Astronomy/Astrophysics Research Centre).

The Deep Spectroscopic Survey utilized NASA/ESA/CSA collaborative Near Infrared Imager/Slitless Spectrograph onboard James Webb Space Telescope supported by UKRI Science/Technology Facilities Council; Fundação para Ciência e Tecnologia FCT; US National Science Foundation/National Research Council Canada contributions acknowledged accordingly.