13 research outputs found
Main-Belt Comet P/2012 T1 (PANSTARRS)
We present initial results from observations and numerical analyses aimed at
characterizing main-belt comet P/2012 T1 (PANSTARRS). Optical monitoring
observations were made between October 2012 and February 2013 using the
University of Hawaii 2.2 m telescope, the Keck I telescope, the Baade and Clay
Magellan telescopes, Faulkes Telescope South, the Perkins Telescope at Lowell
Observatory, and the Southern Astrophysical Research (SOAR) telescope. The
object's intrinsic brightness approximately doubles from the time of its
discovery in early October until mid-November and then decreases by ~60%
between late December and early February, similar to photometric behavior
exhibited by several other main-belt comets and unlike that exhibited by
disrupted asteroid (596) Scheila. We also used Keck to conduct spectroscopic
searches for CN emission as well as absorption at 0.7 microns that could
indicate the presence of hydrated minerals, finding an upper limit CN
production rate of QCN<1.5x10^23 mol/s, from which we infer a water production
rate of QH2O<5x10^25 mol/s, and no evidence of the presence of hydrated
minerals. Numerical simulations indicate that P/2012 T1 is largely dynamically
stable for >100 Myr and is unlikely to be a recently implanted interloper from
the outer solar system, while a search for potential asteroid family
associations reveal that it is dynamically linked to the ~155 Myr-old Lixiaohua
asteroid family.Comment: 15 pages, 4 figures, accepted for publication in ApJ Letter
Catastrophic Disruption of Comet ISON
We report submillimeter 450 and 850 μm dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31–0.08 au prior to perihelion on 2013 November 28 (rh = 0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60″ (>105 km) in the anti-solar direction. Deconvolution of the November 28.04 850 μm image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing ∼5.2 × 1010 kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the cometʼs residual nucleus
Catastrophic Disruption of Comet ISON
We report submillimeter 450 and 850 μm dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31–0.08 au prior to perihelion on 2013 November 28 (rh = 0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60″ (>105 km) in the anti-solar direction. Deconvolution of the November 28.04 850 μm image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing ∼5.2 × 1010 kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the cometʼs residual nucleus
WISE/NEOWISE observations of Active Bodies in the Main Belt
We report results based on mid-infrared photometry of 5 active main belt
objects (AMBOs) detected by the Wide-field Infrared Survey Explorer (WISE)
spacecraft. Four of these bodies, P/2010 R2 (La Sagra), 133P/Elst-Pizarro,
(596) Scheila, and 176P/LINEAR, showed no signs of activity at the time of the
observations, allowing the WISE detections to place firm constraints on their
diameters and albedos. Geometric albedos were in the range of a few percent,
and on the order of other measured comet nuclei. P/2010 A2 was observed on
April 2-3, 2010, three months after its peak activity. Photometry of the coma
at 12 and 22 {\mu}m combined with ground-based visible-wavelength measurements
provides constraints on the dust particle mass distribution (PMD), dlogn/dlogm,
yielding power-law slope values of {\alpha} = -0.5 +/- 0.1. This PMD is
considerably more shallow than that found for other comets, in particular
inbound particle fluence during the Stardust encounter of comet 81P/Wild 2. It
is similar to the PMD seen for 9P/Tempel 1 in the immediate aftermath of the
Deep Impact experiment. Upper limits for CO2 & CO production are also provided
for each AMBO and compared with revised production numbers for WISE
observations of 103P/Hartley 2.Comment: 32 Pages, including 5 Figure
Outgassing Behavior of C/2012 S1 (ISON) From September 2011 to June 2013
We report photometric observations for comet C/2012 S1 (ISON) obtained during
the time period immediately after discovery (r=6.28 AU) until it moved into
solar conjunction in mid-2013 June using the UH2.2m, and Gemini North 8-m
telescopes on Mauna Kea, the Lowell 1.8m in Flagstaff, the Calar Alto 1.2m
telescope in Spain, the VYSOS-5 telescopes on Mauna Loa Hawaii and data from
the CARA network. Additional pre-discovery data from the Pan STARRS1 survey
extends the light curve back to 2011 September 30 (r=9.4 AU). The images showed
a similar tail morphology due to small micron sized particles throughout 2013.
Observations at sub-mm wavelengths using the JCMT on 15 nights between 2013
March 9 (r=4.52 AU) and June 16 (r=3.35 AU) were used to search for CO and HCN
rotation lines. No gas was detected, with upper limits for CO ranging between
(3.5-4.5)E27 molec/s. Combined with published water production rate estimates
we have generated ice sublimation models consistent with the photometric light
curve. The inbound light curve is likely controlled by sublimation of CO2. At
these distances water is not a strong contributor to the outgassing. We also
infer that there was a long slow outburst of activity beginning in late 2011
peaking in mid-2013 January (r~5 AU) at which point the activity decreased
again through 2013 June. We suggest that this outburst was driven by CO
injecting large water ice grains into the coma. Observations as the comet came
out of solar conjunction seem to confirm our models.Comment: 8 pages, 2 figures, 3 table
Das Stellarium Gornergrat
Der Gornergrat in der Nähe des Matterhorns in der Schweiz ist einer der besten Standorte für astronomische Forschung in Mitteleuropa. Bis 2010 wurde hier internationale Forschung betrieben, seitdem wird das Observatorium als pädagogisches robotisches Teleskop mit hervorragenden Instrumenten genutzt.Lehrende können für unterschiedliche Altersstufen über ein Webportal verschiedene pädagogische Aktivitäten buchen. Zu jeder Aktivität stehen Erläuterungen, Arbeitsblätter sowie Beobachtungsaufträge zur Verfügung, die von den Lernenden selbstständig online gebucht und daraufhin vom Teleskop eigenständig aufgenommen werden können. Diese sind wenig später auf dem Portal abrufbar und können ausgewertet werden.In diesem Beitrag werden das Grundkonzept des Stellarium Gornergrat sowie einige Beispielaktivitäten vorgestellt
Search for the return of activity in active asteroid 176P/LINEAR
We present the results of a search for the reactivation of active asteroid 176P/LINEAR during its 2011 perihelion passage using deep optical observations obtained before, during, and after that perihelion passage. Deep composite images of 176P constructed from data obtained between 2011 June and 2011 December show no visible signs of activity, while photometric measurements of the object during this period also show no significant brightness enhancements similar to that observed for 176P between 2005 November and 2005 December when it was previously observed to be active. An azimuthal search for dust emission likewise reveals no evidence for directed emission (i.e., a tail, as was previously observed for 176P), while a one-dimensional surface brightness profile analysis shows no indication of a spherically symmetric coma at any time in 2011. We conclude that 176P did not in fact exhibit activity in 2011, at least not on the level on which it exhibited activity in 2005, and suggest that this could be due to the devolatization or mantling of the active site responsible for its activity in 2005