Publications by authors named "H KNUTSON"
Article Synopsis
- Brown dwarf companions to stars help us understand planet formation processes, but some of them are more massive than expected based on their luminosities and host star ages.
- Gliese 229 B, previously thought to be a single entity, was revealed through observations to actually be two brown dwarfs, Gliese 229 Ba and Bb, with masses of 38.1 and 34.4 Jupiter masses, respectively.
- This discovery challenges existing theories and raises questions about the formation and occurrence of binary brown dwarfs in close orbits around stars.
Article Synopsis
- HD 189733b is a key exoplanet for studying atmospheres, providing insights into composition, chemistry, and atmospheric dynamics.
- Previous studies identified molecules like HO and CO in its atmosphere, but some findings about methane have been disputed.
- Recent observations detect HO, CO, and HS, leading to an inferred atmosphere metallicity three to five times that of its star, suggesting formation from water-rich icy planetesimals.
Characterizing rocky exoplanets is a central aim of astronomy, and yet the search for atmospheres on rocky exoplanets has so far resulted in either tight upper limits on the atmospheric mass or inconclusive results. The 1.95R and 8.
View Article and Find Full Text PDFClose-in giant exoplanets with temperatures greater than 2,000 K ('ultra-hot Jupiters') have been the subject of extensive efforts to determine their atmospheric properties using thermal emission measurements from the Hubble Space Telescope (HST) and Spitzer Space Telescope. However, previous studies have yielded inconsistent results because the small sizes of the spectral features and the limited information content of the data resulted in high sensitivity to the varying assumptions made in the treatment of instrument systematics and the atmospheric retrieval analysis. Here we present a dayside thermal emission spectrum of the ultra-hot Jupiter WASP-18b obtained with the NIRISS instrument on the JWST.
View Article and Find Full Text PDFArticle Synopsis
- Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres helps to understand their chemical processes and formation history.
- The James Webb Space Telescope (JWST) allows for advanced observations of exoplanets, notably WASP-39b, providing insights through time-series data with high precision in a new wavelength range.
- Findings include the detection of water vapor in the atmosphere with a high metallicity (1-100 times that of the Sun) and a low C/O ratio, suggesting the potential for significant solid material accretion during formation or chemical disequilibrium in the atmosphere.