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Boehnhardt, H.; Birkle, K.; Fiedler, A.; Jordá, L.; Peschke, S. B.; Rauer, H.; Schulz, R.; Schwehm, G.; Thomas, N.; Tozzi, G. P.; West, R. M.

doi:10.1023/a:1006288630372

Cited by 27 publications

(23 citation statements)

References 7 publications

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“…Some believed the emission to be impact ejecta from a collision between 133P and another asteroid or group of asteroids (e.g., Tóth 2000), while others believed it to be the result of the sublimation of volatile ices on 133P's surface (e.g., Boehnhardt et al 1998). Impact scenarios were unable to plausibly explain the months-long duration of the dust emission episode (Boehnhardt et al 1996); however, while sublimation required the apparently implausible scenario of surface ice surviving to the present day on a main-belt asteroid in quantities sufficient for driving cometary activity.…”

Section: Motivationmentioning

confidence: 99%

The Hawaii trails project: comet-hunting in the main asteroid belt

Hsieh

2009

A&A

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Context. The mysterious solar system object 133P/(7968) Elst-Pizarro is dynamically asteroidal, yet displays recurrent comet-like dust emission. Two scenarios were hypothesized to explain this unusual behavior: 1) 133P is a classical comet from the outer solar system that has evolved onto a main-belt orbit or 2) 133P is a dynamically ordinary main-belt asteroid on which subsurface ice has recently been exposed. If 1) is correct, the expected rarity of a dynamical transition onto an asteroidal orbit implies that 133P could be alone in the main belt. In contrast, if 2) is correct, other icy main-belt objects should exist and could also exhibit cometary activity. Aims. Believing 133P to be a dynamically ordinary, yet icy main-belt asteroid, I set out to test the primary prediction of the hypothesis: that 133P-like objects should be common and could be found by an appropriately designed observational survey. Methods. I conducted just such a survey -the Hawaii Trails Project -of selected main-belt asteroids in a search for objects displaying cometary activity. Optical observations were made of targets selected from among the Themis, Koronis, and Veritas asteroid families, the Karin asteroid cluster, and low-inclination, kilometer-scale outer-belt asteroids, using the Lulin 1.0 m, small and moderate aperture research telescope system (SMARTS) 1.0 m, University of Hawaii 2.2 m, southern astrophysical research (SOAR) 4.1 m, Gemini North 8.1 m, Subaru 8.2 m, and Keck I 10 m telescopes. Results. I made 657 observations of 599 asteroids, discovering one active object now known as 176P/LINEAR, leading to the identification of the new cometary class of main-belt comets (MBCs). These results suggest that there could be ∼100 currently active MBCs among low-inclination, kilometer-scale outer-belt asteroids. Physically and statistically, MBC activity is consistent with initiation by meter-sized impactors. The estimated rate of impacts and sizes of resulting active sites, however, imply that 133P-sized bodies should become significantly devolatilized over Gyr timescales, suggesting that 133P, and possibly the other MBCs as well, could be secondary, or even multigenerational, fragments from recent breakup events.

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Section: Motivationmentioning

confidence: 99%

The Hawaii trails project: comet-hunting in the main asteroid belt

Hsieh

2009

A&A

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“…In an effort to explain EP's mysterious comet-like behavior, Boehnhardt et al (1998) proposed that EP's surface could contain a component of ''icy dirt'' that was disturbed and activated by a recent impact. They did not indicate in detail, however, how such volatile material could survive over gigayear timescales in a main-belt object such as EP.…”

Section: Introductionmentioning

confidence: 99%

The Strange Case of 133P/Elst-Pizarro: A Comet among the Asteroids

2004

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We present a new investigation of the comet-asteroid transition object 133P/(7968) Elst-Pizarro. We find mean optical colors (BÀV = 0.69 AE 0.02, VÀR = 0.42 AE 0.03, RÀI = 0.27 AE 0.03) and a phase-darkening coefficient ( = 0.044 AE 0.007 mag deg À1 ) that are comparable both to other comet nuclei and to C-type asteroids. As in 1996, when this object's comet-like activity was first noted, data from 2002 show a long, narrow dust trail in the projected orbit of the object. Observations over several months reveal changes in the structure and brightness of this trail, showing that it is actively generated over long periods of time. Finson-Probstein modeling is used to constrain the parameters of the dust trail. We find optically dominant dust particle sizes of a d $ 10 m released with low ejection velocities (v g % 1.5 m s À1 ) over a period of activity lasting at least 5 months in 2002. The doublepeaked light curve of the nucleus indicates an aspherical shape (axis ratio a/b ! 1.45 AE 0.07) and rapid rotation (period P rot = 3.471 AE 0.001 hr). The practical identification of 133P/Elst-Pizarro as a comet (i.e., a mass-losing body) is not in doubt, but the origin of the mass loss is unclear. The 1996 trail has been previously explained as debris released by a chance impact, but our discovery of recurrent activity renders this interpretation implausible. We consider two hypotheses for the activity in 133P/ Elst-Pizarro. The ejection of particles is naturally explained if the object is a barely active Jupiter-family comet that has evolved into an asteroid-like orbit, perhaps under the prolonged action of nongravitational forces due to asymmetric mass loss. In this case, the orbital similarity to the Themis family must be considered coincidental. Alternatively, 133P/ Elst-Pizarro could be a true member of the Themis family on which buried ice has been recently excavated by impact.

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“…These objects are most likely native to the asteroid belt (Fernández et al, 2002) and may be activated by a collision with a small body (Boehnhardt et al, 1998;Toth, 2000). Hsieh andJewitt (2005, 2006a) carry out the first survey to search for MBCs and, as of this writing, only three MBCs have been found: 133P/Elst-Pizzaro (Elst et al, 1996), P/2005 U1 (Read et al, 2005) and 176P/LINEAR (Hsieh and Jewitt, 2006b).…”

Section: Introductionmentioning

confidence: 99%

Searching for main-belt comets using the Canada–France–Hawaii Telescope Legacy Survey

Gilbert

Wiegert

2009

Icarus

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The Canada-France-Hawaii Telescope Legacy Survey, specifically the Very Wide segment of data, is used to search for possible main-belt comets. In the first data set, 952 separate objects with asteroidal orbits within the main-belt are examined using a three-level technique. First, the full-width-half-maximum of each object is compared to stars of similar magnitude, to look for evidence of a coma. Second, the brightness profiles of each object are compared with three stars of the same magnitude, which are nearby on the image to ensure any extended profile is not due to imaging variations. Finally, the star profiles are subtracted from the asteroid profile and the residuals are compared with the background using an unpaired Ttest. No objects in this survey show evidence of cometary activity. The second survey includes 11438 objects in the main-belt, which are examined visually. One object, an unknown comet, is found to show cometary activity. Its motion is consistent with being a main-belt asteroid, but the observed arc is too short for a definitive orbit calculation. No other body in this survey shows evidence of cometary activity. Upper limits of the number of weakly and strongly active main-belt comets are derived to be 630±77 and 87±28, respectively. These limits are consistent with those expected from asteroid collisions. In addition, data extracted from the Canada-France-Hawaii Telescope image archive of main-belt comet 176P/LINEAR is presented.

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Cited by 27 publications

References 7 publications

The Hawaii trails project: comet-hunting in the main asteroid belt

The Hawaii trails project: comet-hunting in the main asteroid belt

The Strange Case of 133P/Elst-Pizarro: A Comet among the Asteroids

Searching for main-belt comets using the Canada–France–Hawaii Telescope Legacy Survey

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