New brown dwarf discovered from James Webb early release data

It’s about 30 times larger than Jupiter.
Christopher McFadden
jupiter-dwarf.jpg
Image cutouts of the newly discovered dwarf.

Nonino et al., 2022. 

  • Scientists believe they have found a new distant brown dwarf.
  • The discovery was made using data from the James Webb Space Telescope.
  • The new brown dwarf is about 30 times larger than Jupiter.

A new faint, distant, and cold brown dwarf has been found by a global team of astronomers using the James Webb Space Telescope (JWST). It turns out that the recently discovered object, called GLASS-JWST-BD1, is around 31 times as massive as Jupiter.

The discovery was described in a paper posted on arXiv.org on July 29.

Between planets and stars, brown dwarfs are considered to be intermediate objects. Most astronomers concur that they are substellar objects with masses ranging from 13 to 80 Jupiter masses. T dwarfs are a subtype of brown dwarfs that have effective temperatures of between 500 and 1,500 K. They are the coolest and least luminous substellar objects that have been discovered to date.

Astronomers' understanding of objects close to the contentious planet/star border, including massive exoplanets, may be improved by studying T dwarfs. Although there have been several discoveries of brown dwarfs to date, there have only been 400 discoveries of T dwarfs to date.

In light of this, the newly discovered brown dwarf, most likely belonging to the T dwarf subclass, according to a team of astronomers led by Mario Nonino of the Astronomical Observatory of Trieste in Italy. The finding was made as part of the JWST Early Release Science (ERS) program "Through the Looking GLASS" (GLASS-JWST), which used the Near-Infrared Spectrograph (NIRSPEC), Near-Infrared Imager, and Slitless Spectrograph to study the large galaxy cluster Abell 2744. (NIRISS).

"We present the serendipitous discovery of a late T-type brown dwarf candidate in JWST NIRCam observations of the Early Release Science Abell 2744 parallel field. The discovery was enabled by the sensitivity of JWST at 4 µm wavelengths and the panchromatic 0.9–4.5 µm coverage of the spectral energy distribution," the researchers wrote in the paper.

The brown dwarf is probably about 30 times larger than Jupiter

The study estimates that GLASS-JWST-BD1 has an effective temperature of roughly 600 K and a mass of about 31.43 Jupiter masses. This brown dwarf is thought to be 5 billion years old.

GLASS-JWST-BD1 may be a late-type T dwarf, according to comparisons with theoretical models. Its distance, measured in a direction perpendicular to the galactic plane, was found to be between 1,850 and 2,350 light years. The findings suggest that this object is probably a thick disc or halo object in the Galactic population.

Further studies of GLASS-JWST-BD1 are necessary, the scientists added, in order to confirm that it is a T-dwarf. To learn more about this object's attributes, kinematic or chemical abundance data are required in particular.

The paper's authors highlighted how this discovery shows the JWST's capabilities to study far-off low-mass Galactic stellar and substellar objects in their concluding remarks.

"The large estimated distance of GLASS-JWST-BD1 confirms the power of JWST to probe the very low-mass end of the stellar and substellar mass function in the Galactic thick disk and halo, enabling exploration of metallicity dependence on low-mass star formation and the evolution of brown dwarf atmospheres," the scientists wrote.

You can view the full study for yourself on arXiv.org.

Study abstract:

"We present the serendipitous discovery of a late T-type brown dwarf candidate in JWST NIRCam observations of the Early Release Science Abell 2744 parallel field. The discovery was enabled by the sensitivity of JWST at 4~μm wavelengths and the panchromatic 0.9--4.5~μm coverage of the spectral energy distribution. The unresolved point source has magnitudes F115W = 27.95±0.15 and F444W = 25.84±0.01 (AB), and its F115W−F444W and F356W−F444W colors match those expected for other, known T dwarfs. We can exclude it as a reddened background star, high redshift quasar, or very high redshift galaxy. Comparison with stellar atmospheric models indicates a temperature of Teff ≈ 600~K and surface gravity logg ≈ 5, implying a mass of 0.03~M⊙ and age of 5~Gyr. We estimate the distance of this candidate to be 570--720~pc in a direction perpendicular to the Galactic plane, making it a likely thick disk or halo brown dwarf. These observations underscore the power of JWST to probe the very low-mass end of the substellar mass function in the Galactic thick disk and halo."

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