scholarly journals Fragmenting Active Asteroid 331P/Gibbs

2021 ◽  
Vol 162 (6) ◽  
pp. 268
Author(s):  
David Jewitt ◽  
Jing Li ◽  
Yoonyoung Kim
Keyword(s):  
Hubble Space Telescope ◽  
Effective Radius ◽  
Rotational Instability ◽  
Main Belt ◽  
Subsequent Evolution ◽  
Rapid Rotation ◽  
Primary Nucleus ◽  
Critical Rotation ◽  
Contact Binary ◽  
Nucleus Mass

Abstract We describe active asteroid 331P/Gibbs (2012 F5) using archival Hubble Space Telescope (HST) data taken between 2015 and 2018. 331P is an outer main belt active asteroid with a long-lived debris trail that formed in 2011. Embedded in the debris trail we identify 19 fragments with radii between 0.04 and 0.11 km (albedo 0.05 assumed) containing about 1% of the mass of the primary nucleus. The largest shows a photometric range (∼1.5 mag), a V-shaped minimum, and a two-peaked lightcurve period near 9 hr, consistent with a symmetric contact binary. Less convincing explanations are that 331P-A is a monolithic, elongated splinter or that its surface shows hemispheric 4:1 albedo variations. The debris trail is composed of centimeter-sized and larger particles ejected with characteristic 10 cm s−1 speeds following a size distribution with index q = 3.7 ± 0.1 to 4.1 ± 0.2. The HST data show that earlier, ground-based measurements of the nucleus were contaminated by near-nucleus debris, which cleared by 2015. We find that the primary nucleus has effective radius 0.8 ± 0.1 km and is in rapid rotation (3.26 ± 0.01 hr), with a lightcurve range of 0.25 mag and a minimum density of 1600 kg m−3 if strengthless. The properties of 331P are consistent with (1) formation about 1.5 Myr ago by impact shattering of a precursor body, (2) spin-up by radiation torques to critical rotation, (3) ejection of about 1% of the nucleus mass in mid 2011 by rotational instability, and (4) subsequent evolution of the fragments and dispersal of the debris by radiation pressure.

The long-term evolution of the main asteroidal belt and the origin of large Mars- and Earth-crossers

1999 ◽  
Vol 173 ◽  
pp. 321-323
Author(s):  
D. Nesvorný ◽  
A. Morbidelli
Keyword(s):  
Numerical Simulations ◽  
Time Scales ◽  
Main Belt ◽  
Subsequent Evolution ◽  
Chaotic Process ◽  
The Earth ◽  
Term Evolution ◽  
Asteroidal Belt ◽  
Near Earth Asteroids

AbstractResults of numerical simulations show that the orbits of asteroids in the inner part of the main belt may gradually, subject to a chaotic process acting on 10-100 Myr time scales, become more elliptic and start intersecting the orbit of Mars. The subsequent evolution of an asteroid having close encounters with Mars frequently leads to the Earth-crossing orbit. This revolutionary scenario of the origin of near-Earth asteroids was quantified by Miglioriniet al.(1998) and here we discuss some of the aspects of this work.

scholarly journals HST/STIS imaging of Fomalhaut: New main belt structure and confirmation of Fomalhaut b's eccentric orbit

2013 ◽  
Vol 8 (S299) ◽  
pp. 204-207 ◽  
Author(s):  
P. Kalas ◽  
J. R. Graham ◽  
M. P. Fitzgerald ◽  
M. Clampin
Keyword(s):  
Hubble Space Telescope ◽  
Main Belt ◽  
Contrast Imaging ◽  
Nearby Star ◽  
High Contrast Imaging ◽  
Reflected Light ◽  
New Findings ◽  
Low Mass ◽  
Dust Ring ◽  
Made In

AbstractHigh contrast imaging observations with the Hubble Space Telescope show that the nearby star Fomalhaut is surrounded by a dusty debris belt and a candidate planet, Fomalhaut b, located just inside the edge of the belt. Fomalhaut b has unexpected characteristics, such as a relatively blue spectrum, leading to the hypothesis that the detected object is a low-mass planet hosting a giant planetary dust ring or cloud seen in reflected light. Here we present new HST/STIS observations made in 2010 and 2012 that authenticate the existence of Fomalhaut b. Our MCMC analysis of four epochs of astrometry spread over eight years indicate that the orbit has a~170 AU and e~0.85. Fomalhaut b's orbit is apsidally aligned with the main belt, and periapse is located approximately ~30 AU south of the star. We also show the existence of a ~50 AU wide azimuthal dust depletion in the dust belt. These new findings provide a revised picture of Fomalhaut as a dynamically complex system, where the orbit of Fomalhaut b and the belt structure signify the presence of additional massive planets orbiting the star.

scholarly journals Spinning and colour properties of the active asteroid (6478) Gault

2020 ◽  
Vol 493 (1) ◽  
pp. 70-77 ◽  
Author(s):  
Albino Carbognani ◽  
Alberto Buzzoni
Keyword(s):  
Direct Evidence ◽  
Colour Change ◽  
Optical Observations ◽  
Colour Properties ◽  
Main Belt ◽  
Photometric Observations ◽  
Orbital Phase ◽  
Contact Binary ◽  
The Mean ◽  
Phase Angles

ABSTRACT We report on accurate BVRc observations of (6478) Gault, a 5–6 km diameter inner main-belt asteroid in the Phocaea family, notable for its sporadic, comet-like ejection of dust. This curious behaviour has been mainly interpreted as reconfigurations after YORP spin-up, although merging of a contact binary system cannot be fully excluded. We collected optical observations along the 2019 March–April period, at orbital phase angles between 12° and 21°, to search for direct evidence of asteroid quick spinning rotation. A prevailing period value of 3.34 ± 0.02 h is supported by our and other photometric observations. In the YORP spin-up hypothesis, this period points to a bulk density ρ ≈ 1 $\textrm{g}\, \textrm{cm}^{-3}$. The mean colours are B − V = +0.82±0.3, V − Rc = +0.28±0.06, and B − Rc = +1.11±0.4, but we have observed a trend towards bluer colour during the April session, with about Δ(B − V) ∼ 0.35 ± 0.09 mag. This colour change can be due to asteroid rotation and support the hypothesis that there is a bluer surface under the Gault’s dust.

scholarly journals HUBBLE SPACE TELESCOPE OBSERVATIONS OF MAIN-BELT COMET (596) SCHEILA

2011 ◽  
Vol 733 (1) ◽  
pp. L4 ◽  
Author(s):  
David Jewitt ◽  
Harold Weaver ◽  
Max Mutchler ◽  
Stephen Larson ◽  
Jessica Agarwal
Keyword(s):  
Hubble Space Telescope ◽  
Main Belt ◽  
Space Telescope

scholarly journals Puzzling Snowballs: Main Belt Comets

2012 ◽  
Vol 10 (H16) ◽  
pp. 139-139
Author(s):  
Bin Yang ◽  
Karen Meech
Keyword(s):  
Kuiper Belt ◽  
Oort Cloud ◽  
Rotational Instability ◽  
Main Belt ◽  
Water Ice ◽  
Current State ◽  
Future Space ◽  
Thermally Driven ◽  
Dust Coma ◽  
Surface Ice

AbstractMain belt comets (MBCs) are a class of newly discovered objects that exhibit comet-like appearances and yet are dynamically indistinguishable from ordinary main belt asteroids. The measured size and albedo of MBCs are similar to those of classical comets. At present, six MBCs have been discovered, namely 133P/Elst-Pizarro, 176P/LINEAR, 238P/Read, P/2008 R1, P/La Sagra and P/2006 VW139. The total number of active MBCs is estimated to be at the level of a few hundreds (Hsieh & Jewitt, 2006). Several explanations for the activity of MBCs have been suggested. These include impact ejection, sublimation and rotational instability. However, since renewed activity has been observed in 133P and 238P at successive perihelion passages, the most likely explanation may be a thermally-driven process - e.g sublimation of exposed surface ice. Although the proximity of MBCs to the Sun (r ~ 3 AU) makes the survival of surface ice improbable, thermal models have shown that water ice is thermally stable under a regolith layer a few meters thick. The study of MBCs has recently been complicated by the discoveries of two asteroid collisional events (P/2010 A2 (LINEAR) and (596) Scheila) in 2010, where comet-like dust coma/tail have been attributed to recent impacts. If MBCs are indeed icy, they represent the closest and the third established reservoir of comets (after the Oort cloud and the Kuiper belt). As such, they may have been an important source of water for the Earth's oceans. I will review the current state of MBC studies, present the latest observational results and discuss possible mechanisms that could produce the observed activity. I will also talk about current and future space missions that are dedicated or closely related to MBC studies.

scholarly journals Structural Models for Beta Lyrae-Type Disks

1982 ◽  
Vol 69 ◽  
pp. 261-273
Author(s):  
R.E. Wilson
Keyword(s):  
Structural Models ◽  
Gravitational Energy ◽  
Stellar Structure ◽  
Central Temperature ◽  
Rapid Rotation ◽  
Potential Formulation ◽  
Disk Mass ◽  
Lower Disk ◽  
Contact Binary ◽  
Distorted Geometry

AbstractEquilibrium structural models are computed for a thick, selfgravitating disk in a binary system. Accretion onto the star is limited by the star's rapid rotation (the system is a double-contact binary). The potential formulation is taken from a previous paper, and represents the gravitational potential as that of a massive wire. Corrections to the stellar structure differential equations for the distorted geometry are applied, and the equations are integrated and solved by the fitting point method. The energy is supplied by viscosity. Energy transfer is by convection, and is appreciably superadiabatic throughout the disk. A mass of 0.5 Mʘ is assumed. Representative results are: “central” temperature, 67000 K; “central” pressure, 5 x 1011 dynes/cm2; “equal volume” radius, 17 Rʘ; luminosity, 5 x 103 Lʘ. The model “radius” is in excellent agreement with the observational value for β Lyrae. The model luminosity is slightly higher than the available rate of expenditure of gravitational energy, indicating that a lower disk mass (perhaps 0.25 Mʘ) should be tried.

scholarly journals New active asteroid (6478) Gault

2019 ◽  
Vol 488 (1) ◽  
pp. L143-L148 ◽  
Author(s):  
Man-To Hui (許文韜) ◽  
Yoonyoung Kim (김윤영) ◽  
Xing Gao (高興)
Keyword(s):  
Light Curve ◽  
Power Law ◽  
Total Mass ◽  
Orbital Motion ◽  
Orbital Plane ◽  
Rotational Instability ◽  
Gravitational Acceleration ◽  
Main Belt ◽  
Short Term ◽  
Curve Variation

ABSTRACT Main-belt asteroid (6478) Gault was observed to show cometary features in early 2019. To investigate the cause, we conducted BVR observations at Xingming Observatory, China, from 2019 January to April. The two tails were formed around 2018 October 26–November 8, and 2018 December 29–2019 January 8, respectively, and consisted of dust grains of ≳20 $\mu$m to 3 mm in radius ejected at a speed of 0.15 ± 0.05 m s−1 and following a broken power-law size distribution bending at grain radius ∼70 $\mu$m (bulk density 1 g cm−3 assumed). The total mass of dust within a 104 km-radius aperture around Gault declined from ∼9 × 106 kg since 2019 January at a rate of 2.28 ± 0.07 kg s−1, but temporarily surged around 2019 March 25, because Earth then crossed the orbital plane of Gault, near which the ejected dust was mainly distributed. No statistically significant colour or short-term light-curve variation was seen. Nonetheless we argue that Gault is currently subjected to rotational instability. Using the available astrometry, we did not detect any non-gravitational acceleration in the orbital motion of Gault.

scholarly journals Discovery of a near-infrared bar and a pseudo-bulge in the collisional ring galaxy Cartwheel

2020 ◽  
Vol 497 (1) ◽  
pp. 44-51
Author(s):  
Sudhanshu Barway ◽  
Y D Mayya ◽  
Aitor Robleto-Orús
Keyword(s):  
Morphological Analysis ◽  
Near Infrared ◽  
Hubble Space Telescope ◽  
Major Axis ◽  
Effective Radius ◽  
Semi Major Axis ◽  
Optical Images ◽  
Central Bulge ◽  
Axis Length ◽  
Band Image

ABSTRACT We report the discovery of a bar, a pseudo-bulge, and unresolved point source in the archetype collisional ring galaxy Cartwheel using careful morphological analysis of a near-infrared (NIR) Ks-band image of excellent quality (seeing = 0.42″) at the ESO archive. The bar is oval-shaped with a semi-major axis length of 3.23″ (∼2.09 kpc), with almost a flat light distribution along it. The bulge is almost round (ellipticity = 0.21) with an effective radius of 1.62″ (∼1.05 kpc) and a Sersic index of 0.99, parameters typical of pseudo-bulges in late-type galaxies. The newly discovered bar is not recognizable as such in the optical images even with more than a factor of 2 higher spatial resolution of the Hubble Space Telescope, due to a combination of its red colour and the presence of dusty features. The observed bar and pseudo-bulge most likely belonged to the pre-collisional progenitor of the Cartwheel. The discovery of a bar in an archetype collisional ring galaxy Cartwheel is the first observational evidence to confirm the prediction that bars can survive a drop-through collision along with the morphological structures like a central bulge (pseudo).

Brief summary of Kleť photographic search programme for minor planets

1999 ◽  
Vol 173 ◽  
pp. 189-192
Author(s):  
J. Tichá ◽  
M. Tichý ◽  
Z. Moravec
Keyword(s):  
Ccd Camera ◽  
Minor Planet ◽  
Minor Planets ◽  
Main Belt

AbstractA long-term photographic search programme for minor planets was begun at the Kleť Observatory at the end of seventies using a 0.63-m Maksutov telescope, but with insufficient respect for long-arc follow-up astrometry. More than two thousand provisional designations were given to new Kleť discoveries. Since 1993 targeted follow-up astrometry of Kleť candidates has been performed with a 0.57-m reflector equipped with a CCD camera, and reliable orbits for many previous Kleť discoveries have been determined. The photographic programme results in more than 350 numbered minor planets credited to Kleť, one of the world's most prolific discovery sites. Nearly 50 per cent of them were numbered as a consequence of CCD follow-up observations since 1994.This brief summary describes the results of this Kleť photographic minor planet survey between 1977 and 1996. The majority of the Kleť photographic discoveries are main belt asteroids, but two Amor type asteroids and one Trojan have been found.

Improving x-ray map resolution with image restoration techniques

1996 ◽  
Vol 54 ◽  
pp. 598-599
Author(s):  
Richard B. Mott ◽  
John J. Friel ◽  
Charles G. Waldman
Keyword(s):  
Image Restoration ◽  
Hubble Space Telescope ◽  
Extensive Literature ◽  
Small Object ◽  
X Rays ◽  
X Ray ◽  
Mapping Parameters ◽  
The Matrix ◽  
The 1960S ◽  
Map Resolution

X-rays are emitted from a relatively large volume in bulk samples, limiting the smallest features which are visible in X-ray maps. Beam spreading also hampers attempts to make geometric measurements of features based on their boundaries in X-ray maps. This has prompted recent interest in using low voltages, and consequently mapping L or M lines, in order to minimize the blurring of the maps.An alternative strategy draws on the extensive work in image restoration (deblurring) developed in space science and astronomy since the 1960s. A recent example is the restoration of images from the Hubble Space Telescope prior to its new optics. Extensive literature exists on the theory of image restoration. The simplest case and its correspondence with X-ray mapping parameters is shown in Figures 1 and 2.Using pixels much smaller than the X-ray volume, a small object of differing composition from the matrix generates a broad, low response. This shape corresponds to the point spread function (PSF). The observed X-ray map can be modeled as an “ideal” map, with an X-ray volume of zero, convolved with the PSF. Figure 2a shows the 1-dimensional case of a line profile across a thin layer. Figure 2b shows an idealized noise-free profile which is then convolved with the PSF to give the blurred profile of Figure 2c.

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