Dust Tail Research Articles

HUBBLE SPACE TELESCOPEINVESTIGATION OF MAIN-BELT COMET 133P/ELST-PIZARRO

We report new observations of the prototype main-belt comet (active asteroid) 133P/Elst-Pizarro taken at high angular resolution using the Hubble Space Telescope. The object has three main components; a) a point-like nucleus, b) a long, narrow antisolar dust tail and c) a short, sunward anti-tail. There is no resolved coma. The nucleus has a mean absolute magnitude H_V = 15.70+/-0.10 and a lightcurve range 0.42 mag., the latter corresponding to projected dimensions 3.6 x 5.4 km (axis ratio 1.5:1), at the previously measured geometric albedo of 0.05+/-0.02. We explored a range of continuous and impulsive emission models to simultaneously fit the measured surface brightness profile, width and position angle of the antisolar tail. Preferred fits invoke protracted emission, over a period of 150 days or less, of dust grains following a differential power-law size distribution with index 3.25 < q < 3.5 and having a wide range of sizes. Ultra-low surface brightness dust projected in the sunward direction is a remnant from emission activity occurring in previous orbits, and consists of the largest (>cm-sized) particles. Ejection velocities of one micron-sized particles are comparable to the ~1.8 m/s gravitational escape speed of the nucleus, while larger particles are released at speeds less than the gravitational escape velocity. The observations are consistent with, but do not prove, a hybrid hypothesis in which mass loss is driven by gas drag from the sublimation of near-surface water ice, but escape is aided by centripetal acceleration from the rotation of the elongated nucleus. No plausible alternative hypothesis has been identified.

A dynamical analysis of the dust tail of Comet C/1995 O1 (Hale–Bopp) at high heliocentric distances

Comet C/1995 O1 (Hale–Bopp) has provided an unprecedented opportunity to observe a bright comet over a wide range of heliocentric distances. We present here Spitzer Space Telescope observations of Hale–Bopp from 2005 to 2008 that show a distinct coma and tail, the presence of which is uncommon given its large heliocentric distance (21.6AU and 27.2AU, respectively). The morphology of the dust is compared to dynamical models to understand the activity of the comet. Our analysis shows that the shape of Hale–Bopp’s dust tail in these images cannot be explained using the usual Finson–Probstein (solar gravity+solar radiation pressure) dynamical model. Several alternative explanations are explored. The analysis suggests that the most likely cause of the discrepancy is that the dust is being charged by the solar wind, then being affected by the interplanetary magnetic field via the Lorentz force. Though this effect has been explored previously, if correct, this seems to be the first time that the Lorentz force has been required to model a cometary dust tail. The analysis also suggests that Hale–Bopp was actively emitting particles when these images were taken, and the tail characteristics changed between observations.

Removing chlorine of CuCl residue from zinc hydrometallurgy by microwave roasting

Most Zn hydrometallurgy factories adopt Cu2SO4 as a dechlorination reagent from zinc solution nowadays, thus much CuCl residue is produced. The existing process of treating this residue is washing with water or sodium carbonate solution, which would cause a lot of troubles to water treatment and waste discharge. A method of microwave roasting was adopted for dechlorination of CuCl residue. A 1.5 kW microwave roasting equipment with dust collection and tail gas adsorption systems was set up and applied during the experiment. By investigating the effect of temperature, heat preservation time, moisture content of raw material and grain size of samples on the dechlorination, the optimal experimental condition is obtained. When the samples with 2% moisture and <150 μm grain size are microwave roasted at 400 °C for 2 h, the Cl content turns from 14.27% to 1.35% and the dechlorination rate is as high as 90%, while that with conventional heating is only 60%–80%. The phase change of the roasting process investigated with X-ray diffraction verifies that CuCl in CuCl residue is removed by being transformed into CuO.

DISINTEGRATING ASTEROID P/2013 R3

Splitting of the nuclei of comets into multiple components has been frequently observed but, to date, no main-belt asteroid has been observed to break-up. Using the Hubble Space Telescope, we find that main-belt asteroid P/2013 R3 consists of 10 or more distinct components, the largest up to 200 m in radius (assumed geometric albedo of 0.05) each of which produces a coma and comet-like dust tail. A diffuse debris cloud with total mass roughly 2x10^8 kg further envelopes the entire system. The velocity dispersion among the components is about V = 0.2 to 0.5 m/s, is comparable to the gravitational escape speeds of the largest members, while their extrapolated plane-of-sky motions suggest break-up between February and September 2013. The broadband optical colors are those of a C-type asteroid. We find no spectral evidence for gaseous emission, placing model-dependent upper limits to the water production rate near 1 kg/s. Breakup may be due to a rotationally induced structural failure of the precursor body.

KOI-2700b—A PLANET CANDIDATE WITH DUSTY EFFLUENTS ON A 22 hr ORBIT

Kepler planet candidate KOI-2700b (KIC 8639908b) with an orbital period of 21.84 hours exhibits a distinctly asymmetric transit profile, likely indicative of the emission of dusty effluents, and reminiscent of KIC 1255b. The host star has $T_{\rm eff}$ = 4435 K, M = 0.63 $M_\odot$, and R = 0.57 $R_\odot$, comparable to the parameters ascribed to KIC 12557548. The transit egress can be followed for ~25% of the orbital period, and, if interpreted as extinction from a dusty comet-like tail, indicates a long lifetime for the dust grains of more than a day. We present a semi-physical model for the dust tail attenuation, and fit for the physical parameters contained in that expression. The transit is not sufficiently deep to allow for a study of the transit-to-transit variations, as is the case for KIC 1255b; however, it is clear that the transit depth is slowly monotonically decreasing by a factor of ~2 over the duration of the Kepler mission. The existence of a second star hosting a planet with a dusty comet-like tail would help to show that such objects may be more common and less exotic than originally thought. According to current models, only quite small planets with Mp < 0.03 $M_\oplus$ are likely to release a detectable quantity of dust. Thus, any "normal-looking" transit that is inferred to arise from a rocky planet of radius greater than ~1/2 $R_\oplus$ should not exhibit any hint of a dusty tail. Conversely, if one detects an asymmetric transit, due to a dusty tail, then it will be very difficult to detect the hard body of the planet within the transit because, by necessity, the planet must be quite small (i.e., < 0.3 $R_\oplus$).

Continued activity in P/2013 P5 PANSTARRS

The object P/2013 P5 PANSTARRS was discovered in August 2013, displaying a cometary tail, but its orbital elements indicated that it was a typical member of the inner asteroid main belt. We monitored the object from 2013 August 30 until 2013 October 05 using the CFHT 3.6 m telescope (Mauna Kea, HI), the NTT (ESO, La Silla), the CA 1.23 m telescope (Calar Alto), the Perkins 1.8m (Lowell) and the 0.6 m TRAPPIST telescope (La Silla). We measured its nuclear radius to be r < 0:25 0:29 km, and its colours g 0 r 0 = 0:58 0:05 and r 0 i 0 = 0:23 0:06, typical for an S-class asteroid, as expected for an object in the inner asteroid belt and in the vicinity of the Flora collisional family. We failed to detect any rotational light curve with an amplitude <0.05 mag and a double-peaked rotation period <20 h. The evolution of the tail during the observations was as expected from a dust tail. A detailed Finson-Probstein analysis of deep images acquired with the NTT in early September and with the CFHT in late September indicated that the object was active since at least late January 2013 until the time of the latest observations in 2013 September, with at least two peaks of activity around 2013 June 14 10 d and 2013 July 22 3 d. The changes of activity level and the activity peaks were extremely sharp and short, shorter than the temporal resolution of our observations ( 1 d). The dust distribution was similar during these two events, with dust grains covering at least the 1‐1000 m range. The total mass ejected in grains <1 mm was estimated to be 3:0 10 6 kg and 2:6 10 7 kg around the two activity peaks. Rotational disruption cannot be ruled out as the cause of the dust ejection. We also propose that the components of a contact binary might gently rub and produce the observed emission. Volatile sublimation might also explain what appears as cometary activity over a period of 8 months. However, while main belt comets best explained by ice sublimation are found in the outskirts of the main belt, where water ice is believed to be able to survive buried in moderately large objects for the age of the solar system deeply, the presence of volatiles in an object smaller than 300 m in radius would be very surprising in the inner asteroid belt.

Real-Time Flux Density Measurements of the 2011 Draconid Meteor Outburst

During the 2011 outburst of the Draconid meteor shower, members of the Video Meteor Network of the International Meteor Organization (IMO) provided, for the first time, fully automated flux density measurements in the optical domain. The data set revealed a primary maximum at 20:09 UT $\pm$5 min on 8 October 2011 (195.036 deg solar longitude) with an equivalent meteoroid flux density of (118 $\pm$10) x 10^-3 km^-2 h^-1 at a meteor limiting magnitude of +6.5, which is thought to be caused by the 1900 dust trail of comet 21P/Giacobini-Zinner. We also find that the outburst had a full width at half maximum (FWHM) of 80 minutes, a mean radiant position of alpha=262.2 deg, delta=+56.2 deg ($\pm$1.3 deg) and geocentric velocity of v_geo=17.4 km/s ($\pm$0.5 km/s). Finally, our data set appears to be consistent with a small sub-maximum at 19:34 UT $\pm$7 min (195.036 deg solar longitude) which has earlier been reported by radio observations and may be attributed to the 1907 dust trail.

Analysis and interpretation of 15 quarters ofKeplerdata of the disintegrating planet KIC 12557548 b

The Kepler object KIC 12557548 shows irregular eclipsing behaviour with a constant 15.685 hr period, but strongly varying transit depth. In this paper we fit individual eclipses, in addition to fitting binned light curves, to learn more about the process underlying the eclipse depth variation. Additionally, we put forward observational constraints that any model of this planet-star system will have to match. We find two quiescent spells of ~30 orbital periods each where the transit depth is <0.1%, followed by relatively deep transits. Additionally, we find periods of on-off behaviour where >0.5% deep transits are followed by apparently no transit at all. Apart from these isolated events we find neither significant correlation between consecutive transit depths nor a correlation between transit depth and stellar intensity. We find a three-sigma upper limit for the secondary eclipse of 4.9*10^-5, consistent with a planet candidate with a radius of less than 4600 km. Using the short cadence data we find that a 1-D exponential dust tail model is insufficient to explain the data. We improved our model to a 2-D, two-component dust model with an opaque core and an exponential tail. Using this model we fit individual eclipses observed in short cadence mode. We find an improved fit of the data, quantifying earlier suggestions by Budaj (2013) of the necessity of at least two components. We find that deep transits have most absorption in the tail, and not in a disk-shaped, opaque coma, but the transit depth and the total absorption show no correlation with the tail length.

The Tajikistan superbolide of July 23, 2008. I. Trajectory, orbit, and preliminary fall data

AbstractThe results of the atmospheric trajectory, radiant, heliocentric orbit, and preliminary strewn field calculations for an extremely bright slow‐moving fireball are presented. In the evening hours of July 23, 2008, a bright object entered Earth's atmosphere over Tajikistan. The fireball had a −20.3 maximum absolute magnitude and a spectacularly long persistent dust trail remained visible over a widespread region of Tajikistan for about 28 minutes after sunset. The fireball was also recorded by a visible‐light satellite system at 14 h 45 min 25 s UT, and the dust trail was imaged by video and photocameras. A unique aspect of this event is that it was detected by two infrasound and five seismic stations too. The bolide was first recorded at a height of 38.2 km, reached its maximum brightness at a height of 35.0 km, and finished at a height of 19.6 km. The first breakup occurred under an aerodynamic pressure of approximately 1.6 MPa, similar to the values derived for breakups of the scarcely reported meteorite‐dropping bolides. The fireball's trajectory and dynamic results suggest that meteorite survival is likely. The meteoroid followed an Apollo‐like asteroid orbit comparable to those derived for previously recovered meteorites with accurately known orbits.

Will comet 209P/LINEAR generate the next meteor storm?

Previous studies have suggested that Comet 209P/LINEAR may produce strong me- teor activity on Earth on 2014 May 24; however, exact timing and activity level is difficult to estimate due to the limited physical observations of the comet. Here we reanalyze the optical observations of 209P/LINEAR obtained during its 2009 appari- tion. We find that the comet is relatively depleted in dust production, with Af {\rho} at 1 cm level within eight months around its perihelion. This feature suggested that this comet may be currently transitioning from typical comet to a dormant comet. Syn- dyne simulation shows that the optical cometary tail is dominated by larger particles with {\beta} ~ 0.003. Numerical simulations of the cometary dust trails confirm the arrival of particles on 2014 May 24 from some of the 1798-1979 trails. The nominal radiant is at RA 122 +/- 1 deg, Dec 79 +/- 1 deg (J2000) in the constellation of Camelopardalis. Given that the comet is found to be depleted in dust production, we concluded that a meteor storm (ZHR>=1000) may be unlikely. However, our simulation also shows that the size distribution of the arrived particles is skewed strongly to larger particles. Coupling with the result of syndyne simulation, we think that the event, if detectable, may be dominated by bright meteors. We encourage observers to monitor the expected meteor event as it will provide us with rare direct information on the dynamical history of 209P/LINEAR which is otherwise irretrievably lost.

THE EXTRAORDINARY MULTI-TAILED MAIN-BELT COMET P/2013 P5

Hubble Space Telescope observations of main-belt comet P/2013 P5 reveal an extraordinary system of six dust tails that distinguish this object from any other. Observations two weeks apart show dramatic morphological change in the tails while providing no evidence for secular fading of the object as a whole. Each tail is associated with a unique ejection date, revealing continued, episodic mass loss from the 0.24+/-0.04 km radius nucleus over the last five months. As an inner-belt asteroid and probable Flora family member, the object is likely to be highly metamorphosed and unlikely to contain ice. The protracted period of dust release appears inconsistent with an impact origin, but may be compatible with a body that is losing mass through a rotational instability. We suggest that P/2013 P5 has been accelerated to breakup speed by radiation torques.

COMET 17P/HOLMES: CONTRAST IN ACTIVITY BETWEEN BEFORE AND AFTER THE 2007 OUTBURST

A Jupiter-family comet, 17P/Holmes, underwent outbursts in 1892 and 2007. In particular, the 2007 outburst is known as the greatest outburst over the past century. However, little is known about the activity before the outburst because it was unpredicted. In addition, the time evolution of the nuclear physical status has not been systematically studied. Here we study the activity of 17P/Holmes before and after the 2007 outburst through optical and mid-infrared observations. We found that the nucleus highly depleted its near-surface icy component before but became activated after the 2007 outburst. Assuming a conventional 1-um-sized grain model, we derived a surface fractional active area of 0.58% +- 0.14% before the outburst whereas it was enlarged by a factor of ~50 after the 2007 outburst. We also found that large (>=1 mm) particles could be dominant in the dust tail observed around aphelion. Based on the size of the particles, the dust production rate was >=170 kg/s at the heliocentric distance rh = 4.1 AU, suggesting that the nucleus still held active status around the aphelion passage. The nucleus color was similar to that of the dust particles and average for a Jupiter-family comet but different from most Kuiper Belt objects, implying that the color may be inherent to icy bodies in the solar system. On the basis of these results, we concluded that more than 76 m surface materials were blown off by the 2007 outburst.

Comets as solar probes

By rapidly evaporating as they fly through the Sun’s hot outer atmosphere, sungrazing comets reveal an otherwise invisible magnetic field that shapes the very beginnings of the solar wind.

Light-curve analysis of KIC 12557548b: an extrasolar planet with a comet-like tail

An object with a very peculiar light-curve was discovered recently using Kepler data. Authors argue that this object may be a transiting disintegrating planet with a comet like dusty tail. We calculate the light-curves of stars with such planets and take into account the Mie absorption and scattering on spherical dust grains of various sizes assuming realistic dust opacities and phase functions and finite radius of the source of the scattered light. The planet light-curve is reanalysed using long and short cadence Kepler observations from the first 14 quarters. Orbital period of the planet was improved. We prove that the peculiar light-curve of this objects is in agreement with the idea of a planet with a comet like tail. There is an evidence of a quasi periodic long term evolution of the tail. Light-curve has a prominent pre-transit brightening and a less prominent post-transit brightening. Both are caused by the forward scattering and are a strong function of the particle size. This feature enabled us to estimate a typical particle size (radius) in the dust tail of about 0.1-1 micron. However, there is an indication that the particle size changes along the tail. Larger particles better reproduce the pre-transit brightening and transit core while smaller particles are more compatible with the egress and post-transit brightening. Dust density in the tail is a steep decreasing function of the distance from the planet which indicates a significant tail destruction caused by the star. We also argue that the 'planet' does not show uniform behaviour but may have at least two constituents. This light-curve with pre-transit brightening is analogous to the light-curve of $\epsilon$ Aur with mid-eclipse brightening and forward scattering plays a significant role in such eclipsing systems.

Testing protoplanetary disc dispersal with radio emission

We consider continuum free–free radio emission from the upper atmosphere of protoplanetary discs as a probe of the ionized luminosity impinging upon the disc. Making use of previously computed hydrodynamic models of disc photoevaporation within the framework of extreme-ultraviolet (EUV) and X-ray irradiation, we use radiative transfer post-processing techniques to predict the expected free–free emission from protoplanetary discs. In general, the free–free luminosity scales roughly linearly with ionizing luminosity in both EUV- and X-ray-driven scenarios, where the emission dominates over the dust tail of the disc and is partial optically thin at cm wavelengths. We perform a test observation of GM Aur at 14–18 GHz and detect an excess of radio emission above the dust tail to a very high level of confidence. The observed flux density and spectral index are consistent with free–free emission from the ionized disc in either the EUV- or the X-ray-driven scenario. Finally, we suggest a possible route to testing the EUV- and X-ray-driven dispersal model of protoplanetary discs, by combining observed free–free flux densities with measurements of mass-accretion rates. On the point of disc dispersal one would expect to find an |$\dot{M}_*^2$| scaling with free–free flux in the case of EUV-driven disc dispersal or an Ṁ* scaling in the case of X-ray-driven disc dispersal.

Saturnian mean motion resonances in meteoroid streams

Abstract Many previous works have shown the relevance and dynamics of Jovian mean motion resonances (MMR) in various meteoroid streams. These resonant swarms are known to have produced spectacular meteor displays in the past. In this work, we investigate whether any MMR due to Saturn are feasible, and subsequently check whether such effects are strong enough to trap meteoroids so as to cause enhanced meteor phenomena on Earth. Extensive numerical simulations are done on two major meteoroid streams, which are known to exhibit exterior Jovian resonances. The roles of the 1:6 and 5:14 Jovian MMR have already been studied in the Orionids and Leonids, respectively. Now we find strong evidence of 1:3 and 8:9 Saturnian MMR in Orionids and Leonids, respectively. The presence of compact dust trails in real space due to these two Saturnian resonances is confirmed from our calculations.

THE DUST ENVIRONMENT OF MAIN-BELT COMET P/2012 T1 (PANSTARRS)

Main-Belt Comet P/2012 T1 (PANSTARRS) has been imaged using the 10.4m Gran Telescopio Canarias (GTC) and the 4.2m William Herschel Telescope (WHT) at six epochs in the period from November 2012 to February 2013, with the aim of monitoring its dust environment. The dust tails brightness and morphology are best interpreted in terms of a model of sustained dust emission spanning 4 to 6 months. The total dust mass ejected is estimated at $\sim$6--25$\times10^6$ kg. We assume a time-independent power-law size distribution function, with particles in the micrometer to centimeter size range. Based on the quality of the fits to the isophote fields, an anisotropic emission pattern is favored against an isotropic one, in which the particle ejection is concentrated toward high latitudes ($\pm45^\circ$ to $\pm90^\circ$) in a high obliquity object ($I$=80$^\circ$). This seasonally-driven ejection behavior, along with the modeled particle ejection velocities, are in remarkable agreement to those we found for P/2010 R2 (La Sagra) \citep{Moreno11a}.

The 2011 October Draconids outburst – I. Orbital elements, meteoroid fluxes and 21P/Giacobini–Zinner delivered mass to Earth

On October 8th, 2011 the Earth crossed the dust trails left by comet 21P/Giacobini-Zinner during its XIX and XX century perihelion approaches with the comet being close to perihelion. The geometric circumstances of that encounter were thus favorable to produce a meteor storm, but the trails were much older than in the 1933 and 1946 historical encounters. As a consequence the 2011 October Draconid display exhibited several activity peaks with Zenithal Hourly Rates of about 400 meteors per hour. In fact, if the display had been not forecasted, it could have passed almost unnoticed as was strongly attenuated for visual observers due to the Moon. This suggests that most meteor storms of a similar nature could have passed historically unnoticed under unfavorable weather and Moon observing conditions. The possibility of obtaining information on the physical properties of cometary meteoroids penetrating the atmosphere under low-geocentric velocity encounter circumstances motivated us to set up a special observing campaign. Added to the Spanish Fireball Network wide-field all-sky and CCD video monitoring, other high-sensitivity 1/2" black and white CCD video cameras were attached to modified medium-field lenses for obtaining high resolution orbital information. The trajectory, radiant, and orbital data of 16 October Draconid meteors observed at multiple stations are presented. The results show that the meteors appeared from a geocentric radiant located at R.A.=263.0+-0.4 deg. and Dec.=+55.3+-0.3 deg. that is in close agreement with the radiant predicted for the 1873-1894 and the 1900 dust trails. The estimated mass of material from 21P/Giacobini-Zinner delivered to Earth during the six-hours outburst was around 950+-150 kg.

DETECTION OF COMA ACTIVITY OF THE ACO/QUASI-HILDA OBJECT 212P/2000YN30

The quasi-Hilda object, 212P/2000YN30 with a cometary-like orbit, was found to display a dust tail structure between January and March, 2009. From orbital calculations, it is shown that this object could have been an active comet in its past history before being transported to the current orbital configuration in quasi-stable 3:2 resonance with Jupiter.

DYNAMICS OF LARGE FRAGMENTS IN THE TAIL OF ACTIVE ASTEROID P/2010 A2

We examine the motions of large fragments at the head of the dust tail of active asteroid P/2010 A2. In previous work we showed that these fragments were ejected from the primary nucleus in early 2009, either following a hypervelocity impact or by rotationally induced break-up. Here, we follow their positions through a series of Hubble Space Telescope images taken during the first half of 2010. The orbital evolution of each fragment allows us to constrain its velocity relative to the main nucleus after leaving its sphere of gravitational influence. We find that the fragments constituting a prominent X-shaped tail feature were emitted in a direction opposite to the motion of the asteroid and towards the south of its orbital plane. Derived emission velocities of these primary fragments range between 0.02 and 0.3 m/s, comparable to the ~0.08 m/s gravitational escape speed from the nucleus. Their sizes are on the order of decimeters or larger. We obtain the best fits to our data with ejection velocity vectors lying in a plane that includes the nucleus. This may suggest that the cause of the disruption of P/2010 A2 is rotational break-up.