12 research outputs found
Hunting for Hydrated Minerals on Trans-Neptunian Objects
We present new optical reflectance spectra of three potentially silicate-rich
trans-Neptunian Objects (TNOs). These spectra were obtained with the aim of
confirming past hints and detections of 0.7 micron absorption features
associated with the presence of iron-bearing phyllosilicates. Our new spectrum
of 120216 (2004 EW95) presents clearly detected absorption features that are
similar in shape to hydrated mineral absorption bands present in the spectra of
aqueously altered outer main belt asteroids. Four new reflectance spectra of
208996 (2003 AZ84) obtained at separate epochs all appear featureless, but vary
significantly in spectral gradient (between approximately 3.5 %/0.1 micron and
8.5 %/0.1 micron) on a timescale consistent with this object's nominal
rotational period. We report the first four optical reflectance spectra of
90568 (2004 GV9), finding them all to be featureless but consistent with colors
previously reported for this object. We speculate that impacts are the only
mechanism capable of delivering, excavating, or forming hydrated minerals at
the surfaces of TNOs in detectable concentrations; as a result, any deposits of
hydrated minerals on TNOs are predicted to be localized and associated with
impact sites. Globally altered TNOs (as observationally suggested for 2004
EW95) plausibly formed more easily at smaller heliocentric distances (< 15 au)
before being transplanted into the current trans-Neptunian population.Comment: 25 pages, 7 figures, 6 tables, accepted for publication in PSJ, v2
adjusted after proofin
2004 EW_(95): A Phyllosilicate-bearing Carbonaceous Asteroid in the Kuiper Belt
Models of the Solar System's dynamical evolution predict the dispersal of primitive planetesimals from their formative regions among the gas-giant planets due to the early phases of planetary migration. Consequently, carbonaceous objects were scattered both into the outer asteroid belt and out to the Kuiper Belt. These models predict that the Kuiper Belt should contain a small fraction of objects with carbonaceous surfaces, though to date, all reported visible reflectance spectra of small Kuiper Belt Objects (KBOs) are linear and featureless. We report the unusual reflectance spectrum of a small KBO, (120216) 2004 EW_(95), exhibiting a large drop in its near-UV reflectance and a broad shallow optical absorption feature centered at ~700 nm, which is detected at greater than 4σ significance. These features, confirmed through multiple epochs of spectral photometry and spectroscopy, have respectively been associated with ferric oxides and phyllosilicates. The spectrum bears striking resemblance to those of some C-type asteroids, suggesting that 2004 EW_(95) may share a common origin with those objects. 2004 EW95 orbits the Sun in a stable mean motion resonance with Neptune, at relatively high eccentricity and inclination, suggesting it may have been emplaced there by some past dynamical instability. These results appear consistent with the aforementioned model predictions and are the first to show a reliably confirmed detection of silicate material on a small KBO
174P/Echeclus and its Blue Coma Observed Post-outburst
It has been suggested that centaurs may lose their red surfaces and become
bluer due to the onset of cometary activity, but the way in which cometary
outbursts affect the surface composition and albedo of active centaurs is
poorly understood. We obtained consistent visual-near-infrared (VNIR)
reflectance spectra of the sporadically active centaur 174P/Echeclus during a
period of inactivity in 2014 and six weeks after its outburst in 2016 to see if
activity had observably changed the surface properties of the nucleus. We
observed no change in the surface reflectance properties of Echeclus following
the outburst compared to before, indicating that, in this case, any surface
changes due to cometary activity were not sufficiently large to be observable
from Earth. Our spectra and post-outburst imaging have revealed, however, that
the remaining dust coma is not only blue compared to Echeclus, but also bluer
than solar, with a spectral gradient of -7.7+/-0.6% per 0.1 micron measured
through the 0.61-0.88 micron wavelength range that appears to continue up to a
wavelength of around 1.3 micron before becoming neutral. We conclude that the
blue visual color of the dust is likely not a scattering effect, and instead
may be indicative of the dust's carbon-rich composition. Deposition of such
blue, carbon-rich, comatic dust onto a red active centaur may be a mechanism by
which its surface color could be neutralized.Comment: 15 pages, 4 figures, 3 tables, AJ accepted, in pres
2004 EW95: A Phyllosilicate-bearing Carbonaceous Asteroid in the Kuiper Belt
Models of the Solar System's dynamical evolution predict the dispersal of
primitive planetesimals from their formative regions amongst the gas-giant
planets due to the early phases of planetary migration. Consequently,
carbonaceous objects were scattered both into the outer asteroid belt and out
to the Kuiper Belt. These models predict that the Kuiper Belt should contain a
small fraction of objects with carbonaceous surfaces, though to date, all
reported visible reflectance spectra of small Kuiper Belt Objects (KBOs) are
linear and featureless. We report the unusual reflectance spectrum of a small
KBO, (120216) 2004 EW95, exhibiting a large drop in its near-UV reflectance and
a broad shallow optical absorption feature centered at ~700 nm which is
detected at greater than 4-sigma significance. These features, confirmed
through multiple epochs of spectral photometry and spectroscopy, have
respectively been associated with ferric oxides and phyllosilicates. The
spectrum bears striking resemblance to those of some C-type asteroids,
suggesting that 2004 EW95 may share a common origin with those objects. 2004
EW95 orbits the Sun in a stable mean motion resonance with Neptune, at
relatively high eccentricity and inclination, suggesting it may have been
emplaced there by some past dynamical instability. These results appear
consistent with the aforementioned model predictions and are the first to show
a reliably confirmed detection of silicate material on a small KBO.Comment: 8 pages, 3 figures, 1 table, accepted, in pres
Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 ‘Oumuamua
During the formation and evolution of the Solar System, significant numbers of cometary and asteroidal bodies were ejected into interstellar space. It is reasonable to expect that the same happened for planetary systems other than our own. Detection of such interstellar objects would allow us to probe the planetesimal formation processes around other stars, possibly together with the effects of long-term exposure to the interstellar medium. 1I/2017 U1 ‘Oumuamua is the first known interstellar object, discovered by the Pan-STARRS1 telescope in October 2017. The discovery epoch photometry implies a highly elongated body with radii of ~ 200 × 20 m when a comet-like geometric albedo of 0.04 is assumed. The observable interstellar object population is expected to be dominated by comet-like bodies in agreement with our spectra, yet the reported inactivity of 'Oumuamua implies a lack of surface ice. Here, we report spectroscopic characterization of ‘Oumuamua, finding it to be variable with time but similar to organically rich surfaces found in the outer Solar System. We show that this is consistent with predictions of an insulating mantle produced by long-term cosmic ray exposure. An internal icy composition cannot therefore be ruled out by the lack of activity, even though ‘Oumuamua passed within 0.25 au of the Sun
2004 EW_(95): A Phyllosilicate-bearing Carbonaceous Asteroid in the Kuiper Belt
Models of the Solar System's dynamical evolution predict the dispersal of primitive planetesimals from their formative regions among the gas-giant planets due to the early phases of planetary migration. Consequently, carbonaceous objects were scattered both into the outer asteroid belt and out to the Kuiper Belt. These models predict that the Kuiper Belt should contain a small fraction of objects with carbonaceous surfaces, though to date, all reported visible reflectance spectra of small Kuiper Belt Objects (KBOs) are linear and featureless. We report the unusual reflectance spectrum of a small KBO, (120216) 2004 EW_(95), exhibiting a large drop in its near-UV reflectance and a broad shallow optical absorption feature centered at ~700 nm, which is detected at greater than 4σ significance. These features, confirmed through multiple epochs of spectral photometry and spectroscopy, have respectively been associated with ferric oxides and phyllosilicates. The spectrum bears striking resemblance to those of some C-type asteroids, suggesting that 2004 EW_(95) may share a common origin with those objects. 2004 EW95 orbits the Sun in a stable mean motion resonance with Neptune, at relatively high eccentricity and inclination, suggesting it may have been emplaced there by some past dynamical instability. These results appear consistent with the aforementioned model predictions and are the first to show a reliably confirmed detection of silicate material on a small KBO
Year 1 of the Legacy Survey of Space and Time (LSST): Recommendations for Template Production to Enable Solar System Small Body Transient and Time Domain Science
The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will discover ~6 million solar system planetesimals, providing in total over a billion photometric and astrometric measurements in 6 broad-band filters. Rubin Observatory's automated data reduction pipelines will employ difference imaging; templates representing the static sky will be subtracted from the nightly LSST observations in order to identify transient sources, including solar system moving objects. These templates are expected to be generated by coadding high quality images of the same pointing from the previous year's survey observations. The first year of LSST operations will require a different method for generating templates, if solar system discoveries are to be reported daily like Year 2 and beyond. We make recommendations for template production in the LSST's first year and present the opportunities for solar system small body transient and time domain science enhanced by this change
Near-UV Reddening Observed in the Reflectance Spectrum of High-inclination Centaur 2012 DR 30
Centaurs with high orbital inclinations and perihelia (i > 60 degrees; q >=
15 au) are a small group of poorly understood minor planets that are predicted
to enter the giant planet region of the Solar System from the inner Oort Cloud.
As such they are one of the few samples of relatively unaltered Oort Cloud
material that can currently be directly observed. Here we present two new
reflectance spectra of one of the largest of these objects, 2012 DR30, in order
to constrain its color and surface composition. Contrary to reports that 2012
DR30 has variable optical color, we find that consistent measurements of its
spectral gradient from most new and published datasets at 0.55-0.8 micron agree
with a spectral gradient of S ~ 10+/-1 %/0.1 micron within their uncertainties.
The spectral variability of 2012 DR30 at Near-UV/blue and Near-Infrared
wavelengths, however, is still relatively unconstrained; self-consistent
rotationally resolved followup observations are needed to characterise any
spectral variation in those regions. We tentatively confirm previous detections
of water ice on the surface of 2012 DR30 , and also consistently observe a
steady steepening of the gradient of its spectrum from wavelengths of around
0.6 micron towards Near-UV wavelengths. Plausible surface materials responsible
for the observed reddening may include ferric oxides contained within
phyllosilicates, and aromatic refractory organics.Comment: 18 pages, 5 figures, 6 tables. Accepted for publication in PS
Limits on Optical Counterparts to the Repeating Fast Radio Burst 20180916B from High-speed Imaging with Gemini-North/‘Alopeke
We report on contemporaneous optical observations at ≈10 ms timescales from the fast radio burst (FRB) 20180916B of two repeat bursts (FRB 20201023 and FRB 20220908) taken with the ‘Alopeke camera on the Gemini-North telescope. These repeats have radio fluences of 2.8 and 3.5 Jy ms, respectively, approximately in the lower 50th percentile for fluence from this repeating burst. The ‘Alopeke data reveal no significant optical detections at the FRB position and we place 3 σ upper limits to the optical fluences of <8.3 × 10 ^−3 and <7.7 × 10 ^−3 Jy ms after correcting for line-of-sight extinction. Together, these yield the most sensitive limits to the optical-to-radio fluence ratio of an FRB on these timescales with η _ν < 3 × 10 ^−3 by roughly an order of magnitude. These measurements rule out progenitor models where FRB 20180916B has a similar fluence ratio to optical pulsars, such as the Crab pulsar, or where optical emission is produced as inverse-Compton radiation in a pulsar magnetosphere or young supernova remnant. Our ongoing program with ‘Alopeke on Gemini-North will continue to monitor repeating FRBs, including FRB 20180916B, to search for optical counterparts on millisecond timescales