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A new class of exoplanets has emerged: the ultra hot Jupiters, the hottest close-in gas giants. Most of them have weaker than expected spectral features in the $1.1-1.7\mu m$ bandpass probed by HST/WFC3 but stronger spectral features at…
We present the discovery of CWISE J050626.96$+$073842.4 (CWISE J0506$+$0738), an L/T transition dwarf with extremely red near-infrared colors discovered through the Backyard Worlds: Planet 9 citizen science project. Photometry from UKIRT…
The crystalline state of water ice in the Solar System depends on the temperature history of the ice and the influence of energetic particles to which it has been exposed. We measured the infrared absorption spectra of amorphous and…
Optical observations of the Oort cloud comet C/2017 K2 (PANSTARRS) show that its activity began at large heliocentric distances (up to 35 au), which cannot be explained by either the sublimation or the crystallization of water ice.…
The continuing difficulty of achieving a reliable explosion in simulations of core-collapse supernovae, especially for more massive stars, has led to speculation concerning the observable transients that might be produced if such a…
Aptly named, ice giants such as Uranus and Neptune contain significant amounts of water. While this water cannot be present near the cloud tops, it must be abundant in the deep interior. We investigate the likelihood of a liquid water ocean…
Water is predicted to be among, if not the most abundant molecular species after hydrogen in the atmospheres of close-in extrasolar giant planets (hot-Jupiters) Several attempts have been made to detect water on an exoplanet, but have…
We calculate the frequencies of collective modes of neutrons, protons and electrons in the outer core of neutron stars. The neutrons and protons are treated in a hydrodynamic approximation and the electrons are regarded as collisionless.…
Understanding the intrinsic colors of Type Ia supernovae (SNe Ia) is important to their use as cosmological standard candles. Understanding the effects of reddening and redshift on the observed colors are complicated and dependent on the…
We discuss the possibility that the recent detection of 511 keV gamma rays from the galactic bulge, as observed by INTEGRAL, can be naturally explained by the supermassive very dense droplets (strangelets) of dark matter. These droplets are…
Nitrogen, carbon monoxide, and methane are key materials in the far outer Solar System where their high volatility enables them to sublimate, potentially driving activity at very low temperatures. Knowledge of their vapor pressures and…
As many as $10^9$ neutron stars populate the Galaxy, but only $\approx 10^3$ are directly observed as pulsars or as accreting sources in X-ray binaries. In principle also the accretion of the interstellar medium may make isolated neutron…
Complex organic molecules are key markers of molecular diversity, and their formation conditions in protoplanetary disks remain an active area of research. These molecules have been detected on a variety of celestial bodies, including icy…
X-ray-dim isolated neutron stars (XDINSs), also known as the Magnificent Seven, exhibits a Planck-like soft X-ray spectrum. In the optical/ultraviolet(UV) band, there is an excess of radiation compared to the extrapolation from the X-ray…
Red giants undergo dramatic and complex structural transformations as they evolve. Angular momentum is transported between the core and envelope during this epoch, a poorly understood process. Here, we infer envelope and core rotation rates…
Cool red giants and supergiants are among the most complex and fascinating stars in the Universe. They are bright and large, and thus can be observed to enormous distances allowing us to study the properties of their host galaxies, such as…
Recent discoveries of anomalously bright radar reflections below the Mars South Polar Layered Deposit (SPLD) have sparked new speculation that liquid water may be present below the ice cap. The reflections, discovered in data acquired by…
The accretion of a cloud of hydrogen at the surface of a small, heavy star produces a high energy mostly dissipated by electromagnetic radiation. The combination of the absorption and the redshift of this radiation by hydrogen explains all…
The origins of the colors of Trans-Neptunian Objects (TNOs) represent a crucial unresolved question, central to understanding the history of our Solar System. Recent observational surveys have revealed correlations between the eccentricity…
The well-known leptonic U(1) symmetry of the standard model of quarks and leptons is extended to include a number of new fermions and scalars. The resulting theory has an invisible QCD axion (thereby solving the strong CP problem), a…