22 research outputs found
A chemical survey of exoplanets with ARIEL
Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio
Call on me! Undergraduates' perceptions of voluntarily asking and answering questions in front of large-enrollment science classes.
Allowing students to voluntarily ask and answer questions in front of the whole class are common teaching practices used in college science courses. However, few studies have examined college science students' perceptions of these practices, the extent to which students choose to engage in these practices, and what discourages students from participating. In this study, we surveyed 417 undergraduates at a research-intensive institution about their experiences asking and answering questions in large-enrollment college science courses. Specifically, students answered questions about to what extent they perceive voluntarily asking and answering questions in large-enrollment science courses is helpful to them and why. They also answered questions about to what extent they engage in asking and answering questions in large-enrollment college science courses and what factors could discourage them from participating. Using binary logistic regression, we examined whether there were differences among students of different demographic groups regarding their opinions about asking and answering questions. We found that overwhelmingly students reported that other students voluntarily asking and answering instructor questions is helpful to them. Notably, compared to continuing generation students, first-generation students were more likely to perceive other students asking questions to be helpful. Despite perceiving asking and answering questions to be helpful, over half of students reported that they never ask or answer questions in large-enrollment college science courses during a semester, and women were more likely than men to report never asking questions. We identified fear of negative evaluation, or students' sense of dread associated with being unfavorably evaluated, as a primary factor influencing their decision to answer instructor questions. This work adds to a growing body of literature on student participation in large-enrollment college science courses and begins to uncover underlying factors influencing student participation