Search Publications
Transient Water Vapor at Europa's South Pole
Nimmo, Francis; Saur, Joachim; Roth, Lorenz +4 more
In November and December 2012, the Hubble Space Telescope (HST) imaged Europa's ultraviolet emissions in the search for vapor plume activity. We report statistically significant coincident surpluses of hydrogen Lyman-α and oxygen OI 130.4-nanometer emissions above the southern hemisphere in December 2012. These emissions were persistently found in…
Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
Madhusudhan, Nikku; Burrows, Adam; Fortney, Jonathan J. +13 more
Exoplanets that orbit close to their host stars are much more highly irradiated than their solar system counterparts. Understanding the thermal structures and appearances of these planets requires investigating how their atmospheres respond to such extreme stellar forcing. We present spectroscopic thermal emission measurements as a function of orb…
Prevalence of small-scale jets from the networks of the solar transition region and chromosphere
Weber, M.; Peter, H.; Golub, L. +24 more
As the interface between the Sun’s photosphere and corona, the chromosphere and transition region play a key role in the formation and acceleration of the solar wind. Observations from the Interface Region Imaging Spectrograph reveal the prevalence of intermittent small-scale jets with speeds of 80 to 250 kilometers per second from the narrow brig…
A fast and long-lived outflow from the supermassive black hole in NGC 5548
Kaastra, J. S.; Harrison, F. A.; Nandra, K. +31 more
Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution x-ray and ultraviolet (UV) observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six spa…
A local clue to the reionization of the universe
Heckman, Timothy M.; Leitherer, Claus; Borthakur, Sanchayeeta +1 more
Identifying the population of galaxies that was responsible for the reionization of the universe is a long-standing quest in astronomy. We present a possible local analog that has an escape fraction of ionizing flux of 21%. Our detection confirms the existence of gaps in the neutral gas enveloping the starburst region. The candidate contains a mas…
Hot explosions in the cool atmosphere of the Sun
Peter, H.; Golub, L.; Curdt, W. +20 more
The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that constitute the outer atmosphere, which is now considered a dynamic structured envelope. Recent observations by the Interface Region Imaging Spectrograph (IRIS) reveal that it …
Evidence of nonthermal particles in coronal loops heated impulsively by nanoflares
Golub, L.; Tian, H.; De Pontieu, B. +21 more
The physical processes causing energy exchange between the Sun’s hot corona and its cool lower atmosphere remain poorly understood. The chromosphere and transition region (TR) form an interface region between the surface and the corona that is highly sensitive to the coronal heating mechanism. High-resolution observations with the Interface Region…
Magnetic moment and plasma environment of HD 209458b as determined from Lyα observations
Holmström, Mats; Lammer, Helmut; Kislyakova, Kristina G. +2 more
Transit observations of HD 209458b in the stellar Lyman-α(Lyα) line revealed strong absorption in both blue and red wings of the line interpreted as hydrogen atoms escaping from the planet’s exosphere at high velocities. The following sources for the absorption were suggested: acceleration by the stellar radiation pressure, natural spectral line b…
A VLBI resolution of the Pleiades distance controversy
Stauffer, John R.; Bower, Geoffrey C.; Melis, Carl +2 more
Because of its proximity and its youth, the Pleiades open cluster of stars has been extensively studied and serves as a cornerstone for our understanding of the physical properties of young stars. This role is called into question by the “Pleiades distance controversy,” wherein the cluster distance of 120.2 ± 1.5 parsecs (pc) as measured by the op…
On the origin of near-infrared extragalactic background light anisotropy
Gong, Yan; Cooray, Asantha; Matsuura, Shuji +13 more
Extragalactic background light (EBL) anisotropy traces variations in the total production of photons over cosmic history and may contain faint, extended components missed in galaxy point-source surveys. Infrared EBL fluctuations have been attributed to primordial galaxies and black holes at the epoch of reionization (EOR) or, alternately, intrahal…