y dwarf Archives - Astrobiology

The top panel shows comparisons of the observed spectrum of JADES-GS-BD-11 (black with grey 1σ error bars) and the median retrieved spectrum for both the PH3 and non-PH3 petitRADTRANS (red and green, respectively, with 1σ central credible intervals shaded around the median). The bottom panel shows the difference between the retrieved and observed spectra, divided by the observed uncertainty. The two retrieved median spectra are generally within 1σ of each other everywhere except at 4.3 µm (the Q-branch of the PH3 feature).-- [astro-ph.SR]

JWST/NIRSpec Spectra for Three Ultracool Brown Dwarfs Detected in Extragalactic Surveys: Further Evidence for Phosphine Absorption

by Keith CowingAugust 19, 2026August 19, 2026

[astro-ph.SR] We present JWST NIRSpec prism spectra for three ultracool brown dwarfs discovered in extragalactic survey data, two from the JWST Advanced Deep Extragalactic Survey (JADES), and one from Public […]

Top: time-series unWISE and Spitzer cutouts with no template subtraction applied, showing SMDET-1’s northeasterly motion over ≈ 12 years.

SMDET-1: A Nearby Y Dwarf Candidate

by Keith CowingAugust 5, 2026August 5, 2026

[astro-ph.SR] We present the discovery of SMDET-1, a red, fast-moving object (μ≈1.3″/yr) identified in time-resolved unWISE coadds using a pixel-level deep learning methodology called SMDET.

Cold Brown Dwarf Full image and caption Credit: NASA/JPL-Caltech

Brown Dwarfs, Exoplanets, -moons, -comets, Gas Giants, Imaging & Spectroscopy, Status Report

The Coldest Known Y Dwarfs: Estimates of their Effective Temperatures

by Keith CowingMarch 29, 2026March 29, 2026

For a decade there has been a factor of 2.5 gap in luminosity between the 275K WISE J085510.83-071442.5 (Luhman 2014) and all other Y dwarfs, with Teff >= 350K. Recently […]

The top panel shows the synthetic spectrum for a Y dwarf at 10 pc with the atmospheric parameters given in the legend. WISE and JWST filter bandpasses are illustrated as red and yellow lines respectively. The middle and lower panels show the ratio of this spectrum divided by a spectrum where the surface gravity has been reduced, and by a spectrum where the metallicity is reduced, respectively. The total energy emitted by the lower gravity dwarf is greater because the radius is larger (Marley et al. 2021), hence the average value in the middle panel is < 1. Note that all three models have similar flux levels averaged over the λ ≈ 4.5 µm flux peak, for example through an imaging filter, although the strength of the absorption features at these wavelengths (primarily due to CO and CO2) are sensitive to gravity. See Section 3 for further discussion. -- astro-ph.SR

Astronomy & Telescopes, Atmospheres, Climate, Weather, Brown Dwarfs, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Redshifting the Study of Cold Brown Dwarfs and Exoplanets: the Mid-Infrared Wavelength Region as an Indicator of Surface Gravity and Mass

by Keith CowingNovember 18, 2024November 18, 2024

JWST is opening many avenues for exploration. For cold brown dwarfs and exoplanets, JWST has opened the door to the mid-infrared wavelength region, where such objects emit significant energy.

Simulated thermal emission spectra from 0.6 to 15 µm of a CARMA model, EddySed models with various Scloud values and different fractions of the cloud mass mixing ratio, and a cloud-free model for a Y dwarf with Teff = 175 K, log(g) = 4.5 and fsed = 6. The inset highlights the region of interest between 3.5 - 6 µm. -- astro-ph.EP

Atmospheres, Climate, Weather, Brown Dwarfs, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Microphysical Prescriptions for Parameterized Water Cloud Formation on Ultra-cool Substellar Objects

by Keith CowingAugust 20, 2024

Water must condense into ice clouds in the coldest brown dwarfs and exoplanets. When they form, these icy clouds change the emergent spectra, temperature structure, and albedo of the substellar […]

Exoplanets, -moons, -comets

Water Clouds in Y Dwarfs and Exoplanets

by Keith CowingApril 2, 2014

The formation of clouds affects brown dwarf and planetary atmospheres of nearly all effective temperatures. Iron and silicate condense in L dwarf atmospheres and dissipate at the L/T transition. Minor […]