Europa's Optical Aurora

Auroral emissions provide opportunities to study the tenuous atmospheres of Solar System satellites, revealing the presence and abundance of molecular and atomic species as well as their spatial and temporal variability. Far-UV aurorae have been used for decades to study the atmospheres of the galilean satellites. Here we present the first detection of Europa's visible-wavelength atomic oxygen aurora at 6300/6364 \AA{} arising from the metastable O$(^1$D) state, observed with the Keck I and Hubble Space Telescopes while Europa was in eclipse by Jupiter on six occasions in February-April 2018. The disk-integrated O($^1$D) brightness varies from $<$500 R up to more than 2 kR between dates, a factor of 15 higher than the OI 1356 \AA{} brightness on average. The ratio of emission at 6300/5577 \AA{} is diagnostic of parent molecule; the 5577 \AA{} emission was not detected in our dataset, which favors O$_2$ as the dominant atmospheric constituent and rules out an O/O$_2$ mixing ratio above 0.35. For an O$_2$ atmosphere and typical plasma conditions at Europa's orbit, the measured surface brightness range corresponds to column densities of 1-9$\times$10$^{14}$ cm$^{-2}$

Europa’s Optical Aurora: Update from Four New Hubble Eclipse Observations

Atomic emissions from the tenuous atmosphere of Jupiter's moon Europa provide information on the composition, column density, and variability of gas species, which inform our understanding of the atmosphere's origins. The strength and ratios of the UV and optical oxygen emission lines indicate that Europa's atmosphere is composed primarily of O_2 and has a column density of ~1–15 × 10^(14) cm^(−2) (Hall et al. 1998; Roth et al. 2014, 2016; de Kleer & Brown 2018). The auroral emissions show variability on timescales from minutes to days, some of which can be attributed to Europa's position relative to Jupiter's plasma sheet (Roth et al. 2016; de Kleer & Brown 2018). The atmosphere is sourced from Europa's surface, from which material is liberated via sputtering and/or thermal processes (Johnson 1990; Oza et al. 2018)

High Spatial and Spectral Resolution Observations of the Forbidden 1.707 μm Rovibronic SO Emissions on Io: Evidence for Widespread Stealth Volcanism

We present observations obtained with the 10 m Keck telescopes of the forbidden SO a¹Δ → X³Σ⁻ rovibronic transition at 1.707 μm on Io while in eclipse. We show its spatial distribution at a resolution of ~0.”12 and a spectral resolution of R ~ 2500, as well as disk-integrated spectra at a high spectral resolution (R ~ 15,000). Both the spatial distribution and the spectral shape of the SO emission band vary considerably across Io and over time. In some cases the SO emissions either in the core or the wings of the emission band can be identified with volcanoes, but the largest areas of SO emissions usually do not coincide with known volcanoes. We suggest that the emissions are caused by a large number of stealth plumes, produced through the interaction of silicate melts with superheated SO₂ vapor at depth. The spectra, in particular the elevated wing of the emission band near 1.69 μm, and their spatial distribution strongly suggest the presence of nonlocal thermodynamic equilibrium processes in addition to the direct ejection of excited SO from the (stealth and other) volcanic vents

Photometry and transit-timing analysis for eleven transiting exoplanets

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2009.Includes bibliographical references (leaves 101-102).This thesis presents time-series photometry of transits of 11 different extrasolar planets. Observations were conducted with the Fred L. Whipple Observatory 1.2m telescope and the Wise Observatory im telescope, in standard optical bandpasses. The number of transits observed for each planet ranges between one and 20 transits, and differential aperture photometry is performed for each transit observation. For the system TrES-2, this thesis examines 14 different different transit observations. Because of this large quantity of data, the parameters Rp/R., b, a/R., and i are also fitted for with precision using the Markov Chain Monte Carlo technique, and the resultant parameter values are presented. Transit-timing analysis is performed on all systems: CoRoT-2, GJ436, HAT-P-1, HD17156, HD189733, TrES-1, TrES-2, WASP-2, WASP-3, XO-1, XO-2, and XO-3. Transit timing is important both for constraining the orbital period and to search for variations in the transit-to-transit interval that could indicate the presence of an unseen companion planet. The transit center times for nearly all observations are found, and the planetary periods for all systems are calculated. In many cases these periods are determined with much greater precision than previously known. It is found that systems XO-2 and HAT-P-1 are consistent with a constant period, but our data are not conclusive with regards to the other systems.by Katherine Rebecca de Kleer.S.B

Europa's Optical Aurora

Auroral emissions provide opportunities to study the tenuous atmospheres of solar system satellites, revealing the presence and abundance of molecular and atomic species as well as their spatial and temporal variability. Far-UV aurorae have been used for decades to study the atmospheres of the Galilean satellites. Here we present the first detection of Europa's visible-wavelength atomic oxygen aurora at 6300/6364 Å arising from the metastable O(^1D) state, observed with the Keck I and Hubble Space Telescope while Europa was in eclipse by Jupiter on six occasions in 2018 February–April. The disk-integrated O(^1D) brightness varies from <500 R up to more than 2 kR between dates, a factor of 15 higher than the O I 1356 Å brightness on average. The ratio of emission at 6300/5577 Å is diagnostic of the parent molecule; the 5577 Å emission was not detected in our data set, which favors O2 as the dominant atmospheric constituent and rules out an O/O_2 mixing ratio above 0.35. For an O_2 atmosphere and typical plasma conditions at Europa's orbit, the measured surface brightness range corresponds to column densities of (1–9) × 10^(14) cm^(−2)

Europa’s Optical Aurora: Update from Four New Hubble Eclipse Observations

Atomic emissions from the tenuous atmosphere of Jupiter's moon Europa provide information on the composition, column density, and variability of gas species, which inform our understanding of the atmosphere's origins. The strength and ratios of the UV and optical oxygen emission lines indicate that Europa's atmosphere is composed primarily of O_2 and has a column density of ~1–15 × 10^(14) cm^(−2) (Hall et al. 1998; Roth et al. 2014, 2016; de Kleer & Brown 2018). The auroral emissions show variability on timescales from minutes to days, some of which can be attributed to Europa's position relative to Jupiter's plasma sheet (Roth et al. 2016; de Kleer & Brown 2018). The atmosphere is sourced from Europa's surface, from which material is liberated via sputtering and/or thermal processes (Johnson 1990; Oza et al. 2018)

Potential for Solar System Science with the ngVLA

Radio wavelength observations of solar system bodies are a powerful method of probing many characteristics of those bodies. From surface and subsurface, to atmospheres (including deep atmospheres of the giant planets), to rings, to the magnetosphere of Jupiter, these observations provide unique information on current state, and sometimes history, of the bodies. The ngVLA will enable the highest sensitivity and resolution observations of this kind, with the potential to revolutionize our understanding of some of these bodies. In this article, we present a review of state-of-the-art radio wavelength observations of a variety of bodies in our solar system, varying in size from ring particles and small near-Earth asteroids to the giant planets. Throughout the review we mention improvements for each body (or class of bodies) to be expected with the ngVLA. A simulation of a Neptune-sized object is presented in Section 6. Section 7 provides a brief summary for each type of object, together with the type of measurements needed for all objects throughout the Solar System