Astronomers have announced their latest discovery – the smallest brown dwarf to date, with only 3 to 4 times the mass of Jupiter. This incredibly light object is classified as one of the "failed stars". Brown dwarfs are not massive enough to start nuclear fusion at their core, and this object is even smaller than some planets. This is the smallest known object to form in a stellar manner.
The formation of stars is through the process of collapse of gas clouds. The stellar nursery is an infinite version of the vast gas cloud, and the overcrowded areas of these places can form stellar objects. Once gravity takes over control, an object with a certain amount of heat and internal pressure generated by the fusion process is formed. The star then begins nuclear fusion, while the brown dwarf remains less hot and active. Exactly how small they can be has long been a matter of debate.
Kevin Luhmann, lead author at Penn State, said in a statement, "In every astronomy textbook, one fundamental question can be found: What is the smallest star? ”
The IC 348 star cluster in the Knowles Cloud is an excellent location to find small brown dwarfs. The cluster is still very young, only 5 million years old. This means that brown dwarfs will still shine in the infrared because of the heat during their formation. Using JWST, the team found three very interesting targets, all of which were less than one-eighth the mass of Jupiter.
The formation of the smallest brown dwarfs poses a challenge to current models. JWST has also spotted some potentially small objects in other regions, such as the Orion Nebula. It is clear that theoretical perspectives will have to be adjusted to account for these observations. The team is confident that these objects are not formed like planets. The other stars around are all quite small, and they have time to form such a massive planet and then kick it into interstellar space.
Co-author Catarina Alveš de Oliveira, from the European Space Agency (ESA), added, "Current models could easily make huge planets in disks around stars. But in this cluster, there is a high probability that this object did not form in the disk, but like a star, and the mass of three Jupiters is 300 times smaller than that of our Sun. So we have to ask, how does the process of star formation work at such a small mass?"
If one record-breaking brown dwarf wasn't enough, the researchers report that two brown dwarfs in the sample exhibit unusual characteristics in the atmosphere. This is a hydroxyl molecule made up of carbon and hydrogen, the composition of which is unknown. The same features can also be seen on Saturn's largest moon - Titan, and in interstellar space.
"This is the first time we have detected such a molecule in the atmosphere of an object outside our solar system," explains Alvish de Oliveira. "Models of brown dwarf atmospheres do not predict their existence. We are looking at younger, lighter objects that we haven't observed before, and we're discovering something new and unexpected. ”
The results of these studies were published in the Journal of Astronomy.