The James Webb Space Telescope has discovered six objects that lie on the border between stars and planets.
Researchers using the James Webb Space Telescope are studying low-mass objects in the reflection nebula NGC 1333, hoping to find a link between star and planet formation. Credit: ESA/Webb, NASA and CSA, A. Scholz, K. Muzic, A. Langeveld, R. Jayawardhana
A team of researchers has used the James Webb Space Telescope (JWST) to discover six possible alien planets. These objects have similar masses to planets, but do not orbit host stars.
The new objects, whose masses range from five to 10 times that of Jupiter, are all located in NGC 1333, a reflection nebula in the constellation Perseus about 960 light-years away that has several star clusters within it. These rogue planets originated in a process that normally forms stars, and they have some of the lowest masses known for objects that formed this way. They add to a growing body of evidence that the physics of what astronomers call “star formation” can also produce smaller planet-like objects with masses several times that of Jupiter.
However, the researchers did not find any objects with masses less than five times that of Jupiter, even though the sensitivity of the JWST would allow them to see them. This leads them to believe that they have identified a threshold: objects lighter than this mass become planets.
The work seeks to “address a fundamental question in astronomy: How can a light object form like a star?” said Johns Hopkins University Chancellor Ray Jayawardhana, an astrophysicist and senior author on the paper. In a statement“It turns out that smaller, free-floating objects that form like stars overlap in mass with giant exoplanets orbiting nearby stars.”
The research is part of the Deep spectroscopic study of young brown dwarfs and free-floating planets and used the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument on JWST. The work is detailed in a paper that was published in arXiv preprint server August 26 and has been accepted for publication in The Astronomical Diary.
What the planets can teach us about the stars
“We’re probing the limits of the star formation process,” said lead author Adam Langeveld, an astrophysicist at Johns Hopkins University. “If we 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 an important context for understanding star and planet formation.”
The least massive of the discovered objects has an estimated mass of five times that of Jupiter, about 1,600 times that of Earth. The presence of a dust disk means the object almost certainly formed as a star, since space dust typically swirls around a central object in the early stages of star formation, Langeveld said.
Some rogue worlds likely originate in molecular clouds. Gravity eventually causes these regions to collapse, and if their masses are large enough, star clusters form. However, not all of these clouds contain enough mass to initiate the process of nuclear fusion, the source of energy in the cores of stars. Another way rogue planets can form is by being ejected from their star systems due to gravitational interactions with other bodies. Although these objects are considered rare in the Milky Way, the new JWST data show that they make up about 10 percent of the celestial bodies in NGC 1333.
In the coming months, the team will study the atmospheres of some of the rogue planets and compare them to those of gas giant planets. Researchers have also been given time aboard JWST to study similar objects with dusty disks and explore the possibility that they are forming mini planetary systems that resemble the numerous moons of Jupiter and Saturn.
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