44 research outputs found
Constraints on the Spin-Pole Orientation, Jet Morphology and Rotation of Interstellar Comet 2I/Borisov with Deep HST Imaging
We present high resolution, deep imaging of interstellar comet 2I/Borisov
taken with the Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3) on 2019
December 8 UTC and 2020 January 27 UTC (HST GO 16040, PI Bolin) before and
after its perihelion passage in combination with HST/WFC3 images taken on 2019
October 12 UTC and 2019 November 16 UTC (HST GO/DD 16009, PI Jewitt) before its
outburst and fragmentation of March 2020, thus observing the comet in a
relatively undisrupted state. We locate 1-2\arcsec~long (2,000 - 3,000 km
projected length) jet-like structures near the optocenter of 2I that appear to
change position angles from epoch to epoch. With the assumption that the jet is
located near the rotational pole supported by its stationary appearance on
10-100 h time frames in HST images, we determine that 2I's pole points
near = 32210, = 3710 ( =
341, = 48) and may be in a simple rotation state.
Additionally, we find evidence for possible periodicity in the HST time-series
lightcurve on the time scale of 5.3 h with a small amplitude of
0.05 mag implying a lower limit on its ratio of 1.5 unlike
the large 2 mag lightcurve observed for 1I/`Oumuamua. However, these
small lightcurve variations may not be the result of the rotation of 2I's
nucleus due to its dust-dominated light-scattering cross-section. Therefore,
uniquely constraining the pre-Solar System encounter, pre-outburst rotation
state of 2I may not be possible even with the resolution and sensitivity
provided by HST observations.Comment: 14 pages, 6 figures and 3 tables, accepted for publication in MNRAS
on 23 July 202
Earth’s Minimoons : Opportunities for Science and Technology
Twelve years ago the Catalina Sky Survey discovered Earth's first known natural geocentric object other than the Moon, a few-meter diameter asteroid designated 2006 RH120. Despite significant improvements in ground-based telescope and detector technology in the past decade the asteroid surveys have not discovered another temporarily-captured orbiter (TCO; colloquially known as minimoons) but the all-sky fireball system operated in the Czech Republic as part of the European Fireball Network detected a bright natural meteor that was almost certainly in a geocentric orbit before it struck Earth's atmosphere. Within a few years the Large Synoptic Survey Telescope (LSST) will either begin to regularly detect TCOs or force a re-analysis of the creation and dynamical evolution of small asteroids in the inner solar system. The first studies of the provenance, properties, and dynamics of Earth's minimoons suggested that there should be a steady state population with about one 1- to 2-m diameter captured objects at any time, with the number of captured meteoroids increasing exponentially for smaller sizes. That model was then improved and extended to include the population of temporarily-captured flybys (TCFs), objects that fail to make an entire revolution around Earth while energetically bound to the Earth-Moon system. Several different techniques for discovering TCOs have been considered but their small diameters, proximity, and rapid motion make them challenging targets for existing ground-based optical, meteor, and radar surveys. However, the LSST's tremendous light gathering power and short exposure times could allow it to detect and discover many minimoons. We expect that if the TCO population is confirmed, and new objects are frequently discovered, they can provide new opportunities for (1) studying the dynamics of the Earth-Moon system, (2) testing models of the production and dynamical evolution of small asteroids from the asteroid belt, (3) rapid and frequent low delta-v missions to multiple minimoons, and (4) evaluating in-situ resource utilization techniques on asteroidal material. Here we review the past decade of minimoon studies in preparation for capitalizing on the scientific and commercial opportunities of TCOs in the first decade of LSST operations.Peer reviewe
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
Pre-discovery Activity of New Interstellar Comet 2I/Borisov Beyond 5 AU
Comet 2I/Borisov, the first unambiguous interstellar comet ever found, was
discovered in August 2019 at au from the Sun on its inbound leg. No
pre-discovery detection beyond 3 au has yet been reported, mostly due to the
comet's proximity to the Sun as seen from the Earth. Here we present a search
for pre-discovery detections of comet Borisov using images taken by the
Catalina Sky Survey (CSS), Pan-STARRS and Zwicky Transient Facility (ZTF), with
a further comprehensive follow-up campaign being presented in
\citet{Bolin2019}. We identified comet Borisov in ZTF images taken in May 2019
and use these data to update its orbit. This allowed us to identify the comet
in images acquired as far back as December 2018, when it was 7.8 au from the
Sun. The comet was not detected in November 2018 when it was 8.6 au from the
Sun, possibly implying an onset of activity around this time. This suggests
that the activity of the comet is either driven by a more volatile species
other than HO, such as CO or CO, or by exothermic crystallization of
amorphous ice. We derive the radius of the nucleus to be km using the
non-detection in November 2018, and estimate an area of --- has been active between December 2018 and September 2019, though
this number is model-dependent and is highly uncertain. The behavior of comet
Borisov during its inbound leg is observationally consistent with dynamically
new comets observed in our solar system, suggesting some similarities between
the two.Comment: AJ in pres
Pre-discovery Activity of New Interstellar Comet 2I/Borisov Beyond 5 AU
Comet 2I/Borisov, the first unambiguous interstellar comet ever found, was discovered in 2019 August at ~3 au from the Sun on its inbound leg. No pre-discovery detection beyond 3 au has yet been reported, mostly due to the comet's proximity to the Sun as seen from the Earth. Here we present a search for pre-discovery detections of comet Borisov using images taken by the Catalina Sky Survey, Pan-STARRS, and the Zwicky Transient Facility (ZTF), with a further comprehensive follow-up campaign being presented in Bolin et al. We identified comet Borisov in ZTF images taken in 2019 May and use these data to update its orbit. This allowed us to identify the comet in images acquired as far back as 2018 December, when it was 7.8 au from the Sun. The comet was not detected in 2018 November when it was 8.6 au from the Sun, possibly implying an onset of activity around this time. This suggests that the activity of the comet is either driven by a more volatile species other than H₂O, such as CO or CO₂, or by exothermic crystallization of amorphous ice. We derive the radius of the nucleus to be <7 km using the non-detection in 2018 November, and estimate an area of ~0.5–10 km² has been active between 2018 December and 2019 September, though this number is model-dependent and is highly uncertain. The behavior of comet Borisov during its inbound leg is observationally consistent with dynamically new comets observed in our solar system, suggesting some similarities between the two