30 research outputs found
The dwarf planet Makemake as seen by X-Shooter
Makemake is one of the brightest known trans-Neptunian objects, as such, it has been widely observed. Nevertheless, its visibility to near-infrared spectrum has not been completely observed in medium-resolving power, aimed at studying in detail the absorption features of CH4 ice. In this paper, we present the spectrum of Makemake observed with X-Shooter at the Very Large Telescope (Chile). We analyse the detected features, measuring their location and depth. Furthermore, we compare Makemake’s spectrum with that of Eris, obtained with the same instrument and similar setup, to conclude that the bands of the CH4 ice in both objects show similar shifts.AAC acknowledges support from the Carlos Chagas Filho Foundation for Research Support of Rio de Janeiro State, FAPERJ (grant E26/203.186/2016), the Brazilian National Council for Scientific and Technological Development, CNPq (grants 304971/2016-2 and 401669/2016-5), and the Universidad de Alicante (contract UATALENTO18-02). ACSF and WMF acknowledge support from the Coordination for the Improvement of Higher Education Personnel, CAPES. NPA acknowledges support from Space Research Initiative/Florida Space Institute funds through the project ‘Digging-Up Ice Rocks in the Solar System’. JLO thanks support from grant AYA2017-89637-R and from the State Agency for Research of the Spanish, MCIU, through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de AstrofÃsica de AndalucÃa (SEV-2017-0709)
Red material on the large moons of Uranus: Dust from irregular satellites?
The large and tidally-locked classical moons of Uranus display longitudinal
and planetocentric trends in their surface compositions. Spectrally red
material has been detected primarily on the leading hemispheres of the outer
moons, Titania and Oberon. Furthermore, detected H2O ice bands are stronger on
the leading hemispheres of the classical satellites, and the leading/trailing
asymmetry in H2O ice band strengths decreases with distance from Uranus. We
hypothesize that the observed distribution of red material and trends in H2O
ice band strengths results from infalling dust from Uranian irregular
satellites. These dust particles migrate inward on slowly decaying orbits,
eventually reaching the classical satellite zone, where they collide primarily
with the outer moons. The latitudinal distribution of dust swept up by these
moons should be fairly even across their southern and northern hemispheres.
However, red material has only been detected over the southern hemispheres of
these moons (subsolar latitude 81 S). Consequently, to test whether irregular
satellite dust impacts drive the observed enhancement in reddening, we have
gathered new ground-based data of the now observable northern hemispheres of
these moons (sub-observer latitudes, 17 to 35 N). Our results and analyses
indicate that longitudinal and planetocentric trends in reddening and H2O ice
band strengths are broadly consistent across both southern and northern
latitudes of these moons, thereby supporting our hypothesis. Utilizing a suite
of numerical best fit models, we investigate the composition of the reddening
agent detected on these moons, finding that both complex organics and amorphous
pyroxene match the spectral slopes of our data. We also present spectra that
span 2.9 to 4.1 microns, a previously unexplored wavelength range in terms of
spectroscopy for the Uranian moons.Comment: Icarus [In Press]. 12 figures, 15 table
Moderate D/H Ratios in Methane Ice on Eris and Makemake as Evidence of Hydrothermal or Metamorphic Processes in Their Interiors: Geochemical Analysis
Dwarf planets Eris and Makemake have surfaces bearing methane ice of unknown
origin. D/H ratios were recently determined from James Webb Space Telescope
(JWST) observations of Eris and Makemake (Grundy et al., submitted), giving us
new clues to decipher the origin of methane. Here, we develop geochemical
models to test if the origin of methane could be primordial, derived from
CO or CO ("abiotic"), or sourced by organics ("thermogenic"). We find that
primordial methane is inconsistent with the observational data, whereas both
abiotic and thermogenic methane can have D/H ratios that overlap the observed
ranges. This suggests that Eris and Makemake either never acquired a
significant amount of methane during their formation, or their original
inventories were removed and then replaced by a source of internally produced
methane. Because producing abiotic or thermogenic methane likely requires
temperatures in excess of ~150{\deg}C, we infer that Eris and Makemake have
rocky cores that underwent substantial radiogenic heating. Their cores may
still be warm/hot enough to produce methane. This heating could have driven
hydrothermal circulation at the bottom of an ice-covered ocean to generate
abiotic methane, and/or metamorphic reactions involving accreted organic matter
could have occurred in response to heating in the deeper interior, generating
thermogenic methane. Additional analyses of thermal evolution model results and
predictions from modeling of D-H exchange in the solar nebula support our
findings of elevated subsurface temperatures and a lack of primordial methane
on Eris and Makemake. It remains an open question whether their D/H ratios may
have evolved subsequent to methane outgassing. Recommendations are given for
future activities to further test proposed scenarios of abiotic and thermogenic
methane production on Eris and Makemake, and to explore these worlds up close.Comment: Submitted to Icarus, 29 pages, 5 figures, 1 tabl
Astro2020 Science White Paper: Triggered High-Priority Observations of Dynamic Solar System Phenomena
Unexpected dynamic phenomena have surprised solar system observers in the
past and have led to important discoveries about solar system workings.
Observations at the initial stages of these events provide crucial information
on the physical processes at work. We advocate for long-term/permanent programs
on ground-based and space-based telescopes of all sizes - including Extremely
Large Telescopes (ELTs) - to conduct observations of high-priority dynamic
phenomena, based on a predefined set of triggering conditions. These programs
will ensure that the best initial dataset of the triggering event are taken;
separate additional observing programs will be required to study the temporal
evolution of these phenomena. While not a comprehensive list, the following are
notional examples of phenomena that are rare, that cannot be anticipated, and
that provide high-impact advances to our understandings of planetary processes.
Examples include: new cryovolcanic eruptions or plumes on ocean worlds; impacts
on Jupiter, Saturn, Uranus, or Neptune; extreme eruptions on Io; convective
superstorms on Saturn, Uranus, or Neptune; collisions within the asteroid belt
or other small-body populations; discovery of an interstellar object passing
through our solar system (e.g. 'Oumuamua); and responses of planetary
atmospheres to major solar flares or coronal mass ejections.Comment: Astro2020 white pape
Physical and dynamical characterization of hyperbolic comet C/2017 U7(PANSTARRS)
We present here a dynamical and observational study of the comet C/2017 U7 (PANSTARRS). This comet was discovered in 2017 and found to have a hyperbolic orbit. Our dynamical analysis shows that the object has probably originated in the Oort cloud, however an interstellar origin cannot be discarded. The observations were obtained in 2018 and 2019 using the Goodman High Throughput Spectrograph (GHTS) at the SOAR telescope. We obtained visible spectra covering the wavelength range of and also images in the SDSS filters system. Both the low-resolution reflectance spectrum and the reflectance spectra derived from the SDSS filters show an atypical band at . We conducted a comparative study of the colors and reflectance spectra of different small body populations (e.g., comets, Centaurs, and trans-Neptunian objects or TNOs) from the literature and concluded that the spectra and the colors of this comet are atypical, showing only some overlap with those of some known members of the TNOs and Centaurs, within the large uncertainties of the measurements of those populations. It is found that the feature and overall spectral shape can be reproduced by laboratory spectra of kerite, a template for aliphatic-rich hydrocarbons that has been previously identified in NIR cometary spectra absorptions. It is tentatively proposed that the unusual spectral shape is the result of a particle size distribution of dust grains in the coma or on the surface that has arisen due to a low grain ejection velocity from the surface and large nucleus size