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Hubble Space Telescope Observations of 3200 Phaethon at Closest Approach
Mutchler, Max; Jewitt, David; Agarwal, Jessica +1 more
We present Hubble Space Telescope observations of the active asteroid (and Geminid stream parent) 3200 Phaethon when at its closest approach to Earth (separation 0.07 au) in 2017 December. Images were recorded within ∼1° of the orbital plane, providing extra sensitivity to low surface brightness caused by scattering from a large-particle trail. We…
FUV Spectral Signatures of Molecules and the Evolution of the Gaseous Coma of Comet 67P/Churyumov-Gerasimenko
Parker, Joel Wm.; Bertaux, Jean-Loup; Stern, S. Alan +10 more
The Alice far-ultraviolet imaging spectrograph onboard Rosetta observed emissions from atomic and molecular species from within the coma of comet 67P/Churyumov-Gerasimenko during the entire escort phase of the mission from 2014 August to 2016 September. The initial observations showed that emissions of atomic hydrogen and oxygen close to the surfa…
ALICE Data Release: A Revaluation of HST-NICMOS Coronagraphic Images
Vigan, Arthur; Choquet, Élodie; Soummer, Rémi +1 more
The Hubble Space Telescope NICMOS instrument was used from 1997 to 2008 to perform coronagraphic observations of about 400 targets. Most of them were part of surveys looking for substellar companions or resolved circumstellar disks to young nearby stars, making the NICMOS coronagraphic archive a valuable database for exoplanets and disks studies. …
Jupiter’s Mesoscale Waves Observed at 5 µm by Ground-based Observations and Juno JIRAM
Fletcher, Leigh N.; Kraaikamp, E.; Hueso, R. +12 more
We characterize the origin and evolution of a mesoscale wave pattern in Jupiter’s North Equatorial Belt (NEB), detected for the first time at 5 µm using a 2016-17 campaign of “lucky imaging” from the VISIR instrument on the Very Large Telescope and the NIRI instrument on the Gemini observatory, coupled with M-band imaging from Juno’s JIRAM i…
The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium
McQuinn, Kristen B. W.; Cannon, John M.; Salzer, John J. +12 more
We present new high-resolution H I spectral line imaging of Coma P, the brightest H I source in the system HI 1232+20. This galaxy with extremely low surface brightness was first identified in the ALFALFA survey as an “(Almost) Dark” object: a clearly extragalactic H I source with no obvious optical counterpart in existing optical survey data (alt…
The Young Massive Star Cluster Westerlund 2 Observed with MUSE. I. First Results on the Cluster Internal Motion from Stellar Radial Velocities
Grebel, Eva K.; Kamann, Sebastian; McLeod, Anna Faye +7 more
Westerlund 2 (Wd2) is the central ionizing star cluster of the H II region RCW 49 and the second most massive young star cluster ({\text{}}M=(3.6+/- 0.3)× {10}4 {\text{}}{M}⊙ ) in the Milky Way. Its young age (∼2 Myr) and close proximity to the Sun (∼4 kpc) makes it a perfect target to study stars emerging from their parental…
Bi-lobed Shape of Comet 67P from a Collapsed Binary
Nesvorný, David; Vokrouhlický, David; Parker, Joel
The Rosetta spacecraft observations revealed that the nucleus of comet 67P/Churyumov-Gerasimenko consists of two similarly sized lobes connected by a narrow neck. Here, we evaluate the possibility that 67P is a collapsed binary. We assume that the progenitor of 67P was a binary and consider various physical mechanisms that could have brought the b…
Probing Oort Clouds around Milky Way Stars with CMB Surveys
Jain, Bhuvnesh; Blake, Cullen H.; Baxter, Eric J.
Long-period comets observed in our solar system are believed to originate from the Oort cloud, which is estimated to extend from roughly a few thousand to 105 au from the Sun. Despite many theoretical arguments for the existence of the Oort cloud, no direct observations of outer Oort cloud objects have been reported. Here, we explore th…
HST Astrometry in the 30 Doradus Region. II. Runaway Stars from New Proper Motions in the Large Magellanic Cloud
Walborn, Nolan R.; van der Marel, Roeland P.; Sana, Hugues +12 more
We present a catalog of relative proper motions for 368,787 stars in the 30 Doradus region of the Large Magellanic Cloud (LMC), based on a dedicated two-epoch survey with the Hubble Space Telescope and supplemented with proper motions from our pilot archival study. We demonstrate that a relatively short epoch difference of three years is sufficien…
Project AMIGA: Distance and Metallicity Gradients along Andromeda’s Giant Southern Stream from the Red Clump
Brown, Thomas M.; Cohen, Roger E.; Gilbert, Karoline M. +7 more
The Giant Southern Stream (GSS) of M31, a keystone signature of a major accretion event, yields crucial constraints on M31 formation and evolution models. Currently, our understanding of the GSS, in terms of both its geometry and its chemistry, results from either wide-field imaging probing only a few magnitudes below the red giant branch tip, or …