Theory suggests that the orbits of some close-in giant planets should decay due to tidal interactions with their host stars. To date, WASP-12b is the only hot Jupiter reported to have a decaying orbit, at a rate of 29 ± 2 ms yr−1. We analyzed data from NASA’s Transiting Exoplanet Survey Satellite (TESS) to verify that WASP-12b’s orbit is indeed changing. We find that the TESS transit and occultation data are consistent with a decaying orbit with an updated period of 1.091420090 ± 0.000000041 days and a decay rate of 32.53 ± 1.62 ms yr−1. We find an orbital decay timescale of . If the observed decay results from tidal dissipation, the modified tidal quality factor is , which falls at the lower end of values derived for binary star systems and hot Jupiters. Our result highlights the power of space-based photometry for investigating the orbital evolution of short-period exoplanets.

Context. The atmospheric and surface characterization of rocky planets is a key goal of exoplanet science. Unfortunately, the measurements required for this are generally out of reach of present-day instrumentation. However, the planet Mercury in our own solar system exhibits a large exosphere composed of atomic species that have been ejected from the planetary surface by the process of sputtering. Since the hottest rocky exoplanets known so far are more than an order of magnitude closer to their parent star than Mercury is to the Sun, the sputtering process and the resulting exospheres could be orders of magnitude larger and potentially detectable using transmission spectroscopy, indirectly probing their surface compositions. Aims. The aim of this work is to search for an absorption signal from exospheric sodium (Na) and singly ionized calcium (Ca + ) in the optical transmission spectrum of the hot rocky super-Earth 55 Cancri e. Although the current best-fitting models to the planet mass and radius require a possible atmospheric component, uncertainties in the radius exist, making it possible that 55 Cancri e could be a hot rocky planet without an atmosphere. Methods. High resolution (R∼110000) time-series spectra of five transits of 55 Cancri e, obtained with three different telescopes (UVES/VLT, HARPS/ESO 3.6m & HARPS-N/TNG) were analysed. Targeting the sodium D lines and the calcium H and K lines, the potential planet exospheric signal was filtered out from the much stronger stellar and telluric signals, making use of the change of the radial component of the orbital velocity of the planet over the transit from −57 to +57 km sec −1 . Results. Combining all five transit data sets, we detect a signal potentially associated with sodium in the planet exosphere at a statistical significance level of 3σ. Combining the four HARPS transits that cover the calcium H and K lines, we also find a potential signal from ionized calcium (4.1 σ). Interestingly, this latter signal originates from just one of the transit measurements -with a 4.9σ detection at this epoch. Unfortunately, due to the low significance of the measured sodium signal and the potentially variable Ca + signal, we estimate the p-values of these signals to be too high (corresponding to <4σ) to claim unambiguous exospheric detections. By comparing the observed signals with artificial signals injected early in the analysis, the absorption by Na and Ca + are estimated to be at a level of ∼ 2.3 × 10 −3 and ∼ 7.0 × 10 −2 respectively, relative to the stellar spectrum.Conclusions. If confirmed, the 3σ signal would correspond to an optically thick sodium exosphere with a radius of 5 R ⊕ , which is comparable to the Roche lobe radius of the planet. The 4.9σ detection of Ca + in a single HARPS data set would correspond to an optically thick Ca + exosphere approximately five times larger than the Roche lobe radius. If this were a real detection, it would imply that the exosphere exhibits extreme variability. Although no formal detection has been made, we advocate th...

Recent observations of the ultra-hot Jupiter WASP-76b have revealed a diversity of atmospheric species. Here we present new high-resolution transit spectroscopy of WASP-76b with GRACES at the Gemini North Observatory, serving as a baseline for the Large and Long Program “Exploring the Diversity of Exoplanet Atmospheres at High Spectral Resolution” (Exoplanets with Gemini Spectroscopy, or ExoGemS for short). With a broad spectral range of 400–1050 nm, these observations allow us to search for a suite of atomic species. We recover absorption features due to neutral sodium (Na i), and report a new detection of the ionized calcium (Ca ii) triplet at ∼850 nm in the atmosphere of WASP-76b, complementing a previous detection of the Ca ii H and K lines. The triplet has line depths of 0.295% ± 0.034% at ∼849.2 nm, 0.574% ± 0.041% at ∼854.2 nm, and 0.454% ± 0.024% at ∼866.2 nm, corresponding to effective radii close to (but within) the planet’s Roche radius. These measured line depths are significantly larger than those predicted by model LTE and NLTE spectra obtained on the basis of a pressure–temperature profile computed assuming radiative equilibrium. The discrepancy suggests that the layers probed by our observations are either significantly hotter than predicted by radiative equilibrium and/or in a hydrodynamic state. Our results shed light on the exotic atmosphere of this ultra-hot world, and will inform future analyses from the ExoGemS survey.

Context. Evaporating rocky exoplanets, such as KIC 12557548b, eject large amounts of dust, which can trail the planet in a comet-like tail. When such objects occult their host star, the resulting transit signal contains information about the dust in the tail. Aims. We aim to use the detailed shape of the Kepler light curve of KIC 12557548b to constrain the size and composition of the dust grains that make up the tail, as well as the mass loss rate of the planet. Methods. Using a self-consistent numerical model of the dust dynamics and sublimation, we calculated the shape of the tail by following dust grains from their ejection from the planet to their destruction due to sublimation. From this dust cloud shape, we generated synthetic light curves (incorporating the effects of extinction and angle-dependent scattering), which were then compared with the phase-folded Kepler light curve. We explored the free-parameter space thoroughly using a Markov chain Monte Carlo method. Results. Our physics-based model is capable of reproducing the observed light curve in detail. Good fits are found for initial grain sizes between 0.2 and 5.6 µm and dust mass loss rates of 0.6 to 15.6 M ⊕ Gyr −1 (2σ ranges). We find that only certain combinations of material parameters yield the correct tail length. These constraints are consistent with dust made of corundum (Al 2 O 3 ), but do not agree with a range of carbonaceous, silicate, or iron compositions. Conclusions. Using a detailed, physically motivated model, it is possible to constrain the composition of the dust in the tails of evaporating rocky exoplanets. This provides a unique opportunity to probe to interior composition of the smallest known exoplanets.

We present high-resolution near-infrared spectra taken during eight transits of 55 Cancri e, a nearby low-density super-Earth with a short orbital period (<18 hr). While this exoplanet’s bulk density indicates a possible atmosphere, one has not been detected definitively. Our analysis relies on the Doppler cross-correlation technique, which takes advantage of the high spectral resolution and broad wavelength coverage of our data, to search for the thousands of absorption features from hydrogen-, carbon-, and nitrogen-rich molecular species in the planetary atmosphere. Although we are unable to detect an atmosphere around 55 Cancri e, we do place strong constraints on the levels of HCN, NH3, and C2H2 that may be present. In particular, at a mean molecular weight of 5 amu, we can rule out the presence of HCN in the atmosphere down to a volume mixing ratio (VMR) of 0.02%, NH3 down to a VMR of 0.08%, and C2H2 down to a VMR of 1.0%. If the mean molecular weight is relaxed to 2 amu, we can rule out the presence of HCN, NH3, and C2H2 down to VMRs of 0.001%, 0.0025%, and 0.08%, respectively. Our results reduce the parameter space of possible atmospheres consistent with the analysis of Hubble Space Telescope/WFC3 observations by Tsiaras et al. and indicate that if 55 Cancri e harbors an atmosphere, it must have a high mean molecular weight or clouds.