Objects straddling the boundary between planets and stars offer new insights into how massive bodies can end up in very short orbits. In a study led by a Czech scientist from the Astronomical Institute of the Czech Academy of Sciences, in collaboration with the Harvard & Smithsonian Center for Astrophysics and Chile\u2019s Universidad Adolfo Ib\u00e1\u00f1ez, astronomers show that while short-period brown dwarfs and hot Jupiters likely do not form in the same way, they may share a similar migration path in young protoplanetary disks.<\/p>\n\n\n\n
An international team of astronomers has now confirmed four new transiting brown dwarfs using data from the TESS space mission and follow-up radial velocity measurements from the FEROS and PLATOSpec spectrographs. \u201cTransiting\u201d means that, as seen from Earth, they regularly pass in front of their star, causing a slight dimming of its light.<\/p>\n\n\n\n
\nWe present four newly validated transiting brown dwarfs identified through TESS photometry and confirmed with high-precision radial velocity measurements obtained from the FEROS and PLATOSpec spectrographs. Notably, three of these companions exhibit orbital periods exceeding 100 days, thereby expanding the sample of long-period transiting brown dwarfs from four to seven systems. The host stars of the long-period brown dwarfs show mild subsolar metallicity. These discoveries highlight the expansion of the metal-poor long-period distribution and help us better understand the brown dwarf desert. In our comparative analysis of eccentricity and metallicity demographics, we utilized catalogs of long-period giant planets, brown dwarfs, and low-mass stellar companions. After accounting for tidal influences, the eccentricity distribution aligns with that of low-mass stellar binaries, presenting a different profile than that observed within the giant planet population. Additionally, the metallicity of the host stars reveals a noteworthy trend: Short-period transiting brown dwarfs are predominantly associated with metal-rich stars, whereas long-period brown dwarfs are more often found around metal-poor stars, thus demonstrating statistical similarities to low-mass stellar hosts. This trend has been previously observed in studies of hot and cold Jupiters and points to a period-coded mixture of channels. A natural explanation is that most brown dwarfs originate from fragmentation at wider separations, with long-period systems retaining this stellar-like imprint, while only those embedded in massive, long-lived metal-rich protoplanetary disks are efficiently delivered and stabilized to short orbits.<\/p>\n<\/blockquote>\n\n\n\n