An international team of astronomers has discovered a new brown dwarf by analyzing data from the Next Generation Transit Survey (NGTS). The newly discovered object, called NGTS-28Ab, completes its orbit of its host star in just 30 hours. The discovery was reported in a paper published on the preprint server on February 15. arXiv.

Brown dwarfs (BDs) are intermediate objects between planets and stars and occupy a mass range from 13 to 80 Jupiter masses (0.012 to 0.076 solar masses). Although many brown dwarfs have been discovered to date, these objects orbiting other stars are a rare find.

Now, a team of astronomers led by Beth A. Henderson of the University of Leicester in the United Kingdom has reported the discovery of such a rare new BD. Using data from NGTS as well as NASA’s Transiting Exoplanet Survey Satellite (TESS), they investigated the binary system known as NGTS-28.

“We identified a brown dwarf for the first time in Next Generation Transit Survey data, confirming observations in TESS sectors 11 and 38,” the researchers wrote in the paper.

The team detected a massive object, an M dwarf known as NGTS-28A, orbiting the parent star in the system. This object was confirmed to be a brown dwarf by follow-up observations from various ground-based facilities, including the South African Astronomical Observatory (SAAO).

The newly discovered brown dwarf is slightly smaller than Jupiter (0.95 Jupiter radius), but is 69 times larger than the largest planet in the Solar System. This gives a density of approximately 98.7 g/cm2. ³ .

According to the article, NGTS-28Ab orbits its host star at a distance of about 0.02 AU every 30.1 hours. The brown dwarf has an equilibrium temperature of about 863 K and is estimated to be at least 500 million years old.

NGTS-28A is approximately half the size and mass of the Sun. Its effective temperature is 3626 K and its age is approximately 7 billion years. The companion NGTS-28B has a similar effective temperature but is about a third smaller and less massive than its host star. The system is located approximately 404 light years away from us.

The results make NGTS-28Ab one of the shortest BD transition periods in the “brown dwarf desert”; the absence of these objects orbiting very close (within 3 AU) of main sequence stars. It turns out that NGTS-28Ab orbits one of the hottest M dwarfs in this desert.

“NGTS-28Ab offers a new opportunity to understand this region in more depth. The brown dwarf desert is thought to result from minimal overlap in the tail of the distribution between planet and star formation mechanisms. Therefore, it is important to model parameters that can indicate the formation of each object.” the study authors concluded.