🌟 A "failed star" ready to fulfill itself

Some astronomical objects seem doomed to be "in-betweens" and remain in the shadow, like brown dwarfs. Too massive to be planets but not heavy enough to ignite into stars, they lead a discreet existence.

However, a recent observation has just shaken up what we thought, by revealing that dynamic processes could offer them an unexpected opportunity to transform into a real star.

Brown dwarfs form similarly to stars, from the collapse of gas and dust clouds, but they don't accumulate enough matter to trigger the nuclear fusion of hydrogen into helium in their core. This absence of nuclear reactions prevents them from shining like the Sun, earning them the sometimes unflattering nickname of failed stars. Their mass is generally between 13 and 80 times that of Jupiter, which is less than that of a typical star.


A team of scientists studied data collected by the Zwicky Transient Facility at the Palomar Observatory, which allowed them to identify a binary system composed of two brown dwarfs in a very tight orbit. This duo, designated ZTF J1239+8347, is located about 1,000 light-years away in the constellation of Ursa Major. The two objects, each with a mass of 60 to 80 times that of Jupiter, orbit so close to each other that the entire system could fit between the Earth and the Moon (between about 238,855 and 251,900 miles (384,400 km) apart).

In this system, one of the brown dwarfs is actively transferring matter to its companion, a process that could allow the receiver to reach the necessary mass to initiate nuclear fusion. Indeed, each of the two brown dwarfs is very close to the mass limit required to become a true star.

This gravitational interaction causes a swelling of the donor object, whose matter flows toward a specific point on the other brown dwarf, creating a heated and bright zone. This region emits a detectable variation in brightness every 57 minutes, a signal that caught the researchers' attention among the billions of objects analyzed.

This type of mass transfer had never been observed before in a pair of brown dwarfs, making it a notable discovery. According to the researchers, these systems could be more common than we think, and future observations with facilities like the Vera Rubin Observatory in Chile could reveal dozens more.

The work of the team, led by Samuel Whitebook of the California Institute of Technology, has been published in The Astrophysical Journal Letters.