The albedo of a celestial body is the fraction of incident starlight reflected by it. The study of the albedos of Solar System objects is at least a century old, at least in the Western world. As examples: Bond (1861) speculated on the near-unity albedo of Jupiter, while Russell (1916) observed the opposition surge of the Moon near and at full phase. The light of a planet or moon varying with...
The helium line at 1083 nm is one of the strongest spectral features observable in transit spectroscopy of exoplanet atmospheres. As such, it is a powerful diagnostic of upper atmospheres of exoplanets, providing valuable insight into their dynamics and the process of atmospheric escape. Absorption in this line is caused by neutral helium atoms in an excited, metastable state. At low densities...
Ultra-hot Jupiters (UHJs) have become prime targets for atmospheric characterisation. KELT-9b is the hottest of the known UHJs and both hydrogen Balmer lines and metal line features have been detected in the planetary transmission spectrum. I will show how NLTE effects drive the temperature pressure structure of KELT-9b's atmosphere and that NLTE effects must be taken into account in order to...
Exoplanet atmospheres provide ideal atmospheric laboratories to explore atmospheres unlike anything in our Solar System. Atmosphere characterisation is also an important tool in understanding exoplanetary system formation and evolution. However, exoplanets are not globally homogeneous, as the light we observe must pass though many diverse regions any observations probe a wide variety of...
The center-to-limb variation (CLV) of the stellar lines across the stellar disk is an important effect for planetary transit spectroscopy. Indeed the variation of spectral line profiles when the planet transits different part of the stellar disk can affect the determination of elemental abundances in the planetary atmospheres, as shown by Yan et al. (2017). Accurately modeling the CLV effect...
High-quality transition probabilities (oscillator strengths, log(gf)) are of vital importance in the analysis of astronomical spectra. Along with spectral line wavelengths and widths, they allow astronomers not only to determine the chemical composition of stellar and exoplanetary atmospheres, but also to gain some insight into their temperature and electron density.
For more than 30 years,...
