Our knowledge of the formation of stars is being called into question by a recently discovered record-breaking object.
With a mass of three to four times that of Jupiter, this brown dwarf looks to be the lowest-mass object of its sort yet found. It is a lonely space object.
Among the many intriguing issues raised by this is the question of how it came to be in the first place.
“Using current models, creating massive planets in a disc around a star is quite simple,” explains European Space Agency astronomer Catarina Alves de Oliveira. However, three Jupiter masses is 300 times smaller than our Sun, thus it would be implausible that this item in this cluster formed in a disk and instead developed like a star. Therefore, we must inquire as to how the star creation process functions at such minuscule masses.”
The term “failed stars” is often applied to brown dwarfs, which is a little derogatory but not totally false. An entity that forms from a dense cluster amid a cloud of gas and dust in space and collapses due to gravity is called a star. It keeps expanding until it reaches a mass large enough for the heat and pressure inside its core to ignite hydrogen fusion. This requires a minimum mass of roughly 80–85 times that of Jupiter.
An object that grows in the same manner but lacks the mass to induce hydrogen fusion is called a brown dwarf. But a brown dwarf isn’t a planet either. The brown in their name really denotes the fact that they are larger than non-glowing “dark” planets and smaller than white dwarf stars. A brown dwarf can fuse atoms of the heavier isotope deuterium, for which the fusion pressure and temperature are lower than those of hydrogen, at a critical mass of roughly 13 Jupiters.
Another method involves the slow accumulation of material left over after a star has finished developing to produce planets. Therefore, something that is too low-mass to start fusion yet originates by gravitational collapse may nevertheless eventually turn into a brown dwarf. These planet-route objects are sometimes referred to as rogue planets, planetary-mass brown dwarfs, or sub-brown dwarfs by astronomers. The goal of a group of astronomers from Pennsylvania State University is to locate the smallest of these objects under the direction of Kevin Luhman.
“One basic question you’ll find in every astronomy textbook is, what are the smallest stars?” Says Luhman. “That’s what we’re trying to answer.”
They surveyed the core of IC 348, a young star cluster located in the Perseus star-forming area approximately 1,000 light-years away, using the James Webb Space Telescope. Compared to stars, sub-brown dwarfs are extremely cool and faint, hence a JWST-caliber infrared telescope is required. They first searched for candidates using the near-infrared NIRCam, and then they examined them using the spectrograph NIRSpec.
With masses ranging from three to eight Jupiters and temperatures ranging from 1100 to 1800 Kelvin (827 to 1527 degrees Celsius, or 1520 to 2780 degrees Fahrenheit), they discovered three additional members of IC 348 that met the criteria. With a mass of about three to four Jupiter, the record-breaker is the smallest of these possibilities. This truly is a riddle. A cloud has a lot of mass, which means it has a lot of gravity for star formation. The formation process would be much more difficult to produce anything the size of a planet because it would begin with a smaller cloud and less gravity, according to the researchers.
Although less likely, the objects may be exoplanets that were forced to leave their planetary systems. The planets in IC 348 are rather massive in comparison to the majority of the stars, which are fairly small. There are also no easy answers for how big planets arise around little stars. In addition, the cluster is quite new. The researchers conclude that planets haven’t had enough time to form and eject themselves thus far from their systems.
Furthermore, that is not the only puzzle. Two of the objects contained an unidentified hydrocarbon, according to the spectrographic study. The signature of this unidentified chemical species has never before been observed in an extrasolar atmosphere, although it has been observed floating around in interstellar space and in the atmospheres of Saturn and Titan in the Solar System. Thus, it’s evident that whatever it is we’re studying here is teaching us something fresh and thought-provoking about the peculiar point at which planets and stars converge.
“This is the first time we’ve detected this molecule in the atmosphere of an object outside our Solar System,” Alves de Oliveira explains. The existence of a brown dwarf atmosphere is not predicted by models. We are witnessing something novel and unexpected when we examine items that have lower masses and younger ages than we have ever seen before.”
