JWST finds a solitary world challenging the distinction between star and planet

Astronomers have discovered six new worlds that look like planets but formed like stars. These so-called “rogue worlds” are between five and 15 times the mass of Jupiter, and one of them may even host the beginnings of a miniature solar system.

Ray Jayawardene Using the James Webb Space Telescope, a researcher from Johns Hopkins University in Maryland and his colleagues discovered these strange worlds in the NGC 1333 star cluster. Despite being planet-sized, none of these worlds orbit a star. This indicates that they likely formed by the collapse of a cloud of dust and gas, similar to how stars like our Sun are born. These objects that form like stars but are not massive enough to sustain the fusion of hydrogen are called brown dwarfs, or failed stars.

“In some ways, the most shocking thing is what we didn't find,” Jayawardene says. “Even though we had the sensitivity to do so, we couldn't find anything with a mass less than five times that of Jupiter.” This may indicate that brown dwarfs can't form at lower masses — that is, they are the smallest objects that can form like stars.

From their observations, the researchers found that about 10 percent of the objects in NGC 1333 are made up of brown dwarfs — a much higher number than expected based on star formation models — and that additional processes, such as turbulence, may be driving the formation of these nomadic planets.

One of the brown dwarfs is particularly unusual, with a ring of dust around it similar to the ones that formed the planets in our solar system. At about five times the mass of Jupiter, it's the smallest planet with such a ring ever found and may mark the beginning of a strange, shrunken planetary system around a dysfunctional star.

“From the miniature world around these objects, [brown dwarf] “It will glow mostly in the infrared, with a very reddish glow, and over hundreds of millions of years it will gradually fade away and become invisible,” Jayawardene says. As the brown dwarf fades, any planets that form around it will freeze out completely, darkening the entire system and making it a less than promising world for searching for life.

Journal References: Astronomical Journal, Printing