ALBERT

Description: At least 16 fragments were detected in images of comet C/1999 S4 (LINEAR) taken on 5 August 2000 with the Hubble Space Telescope (HST) and on 6 August with the Very Large Telescope (VLT). Photometric analysis of the fragments indicates that the largest ones have effective spherical diameters of about 100 meters, which implies that the total mass in the observed fragments was about 2 x 10(9) kilograms. The comet's dust tail, which was the most prominent optical feature in August, was produced during a major fragmentation event, whose activity peaked on UT 22.8 +/- 0.2 July 2000. The mass of small particles (diameters less than about 230 micrometers) in the tail was about 4 x 10(8) kilograms, which is comparable to the mass contained in a large fragment and to the total mass lost from water sublimation after 21 July 2000 (about 3 x 10(8) kilograms). HST spectroscopic observations during 5 and 6 July 2000 demonstrate that the nucleus contained little carbon monoxide ice (ratio of carbon monoxide to water is less than or equal to 0.4%), which suggests that this volatile species did not play a role in the fragmentation of C/1999 S4 (LINEAR).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Weaver, H A -- Sekanina, Z -- Toth, I -- Delahodde, C E -- Hainaut, O R -- Lamy, P L -- Bauer, J M -- A'Hearn, M F -- Arpigny, C -- Combi, M R -- Davies, J K -- Feldman, P D -- Festou, M C -- Hook, R -- Jorda, L -- Keesey, M S -- Lisse, C M -- Marsden, B G -- Meech, K J -- Tozzi, G P -- West, R -- New York, N.Y. -- Science. 2001 May 18;292(5520):1329-33.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218-2686, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11359001" target="_blank"〉PubMed〈/a〉

Description: Using soft x-ray observations of the bright new comet C/1999 S4 (LINEAR) with the Chandra x-ray observatory, we have detected x-ray line emission created by charge exchange between highly ionized solar wind minor ions and neutral gases in the comet's coma. The emission morphology was symmetrically crescent shaped and extended out to 300,000 kilometers from the nucleus. The emission spectrum contains 6 lines at 320, 400, 490, 560, 600, and 670 electron volts, attributable to electron capture and radiative deexcitation by the solar wind species C(+5), C(+6), N(+7), O(+7), and O(+8). A contemporaneous 7-day soft x-ray light curve obtained using the Extreme Ultraviolet Explorer demonstrates a large increase in the comet's emission coincident with a strong solar flare on 14 and 15 July 2000.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lisse, C M -- Christian, D J -- Dennerl, K -- Meech, K J -- Petre, R -- Weaver, H A -- Wolk, S J -- New York, N.Y. -- Science. 2001 May 18;292(5520):1343-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉University of Maryland, Department of Astronomy, College Park, MD 20742, USA. lisse@astro.umd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11359004" target="_blank"〉PubMed〈/a〉

Description: An image of comet Hale-Bopp (C/1995 O1) in soft x-rays reveals a central emission offset from the nucleus, as well as an extended emission feature that does not correlate with the dust jets seen at optical wavelengths. Neon was found to be depleted in the cometary ice by more than a factor of 25 relative to solar abundance, which suggests that ices in Hale-Bopp formed at (or later experienced) temperatures higher than 25 kelvin. A helium line emission at a wavelength of 584 angstroms was detected and may be attributable to charge transfer of solar wind alpha particles in the cometary coma. Ionized oxygen and another helium line contribute to an emission observed at 538 angstroms.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Krasnopolsky, V A -- Mumma, M J -- Abbott, M -- Flynn, B C -- Meech, K J -- Yeomans, D K -- Feldman, P D -- Cosmovici, C B -- New York, N.Y. -- Science. 1997 Sep 5;277(5331):1488-91.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Catholic University of America, Washington, DC 20064, USA. ys2VK@lepvax.gsfc.nasa.gov 20771, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9278508" target="_blank"〉PubMed〈/a〉

Description: The recently discovered periodic comet Machholz 1986 VIII (1986e) travels closer to the sun than any known planet and any known comet with an orbital period of less than 150 years, thus providing astronomers with a unique object for studying cometary evolution. The comet is spiraling steadily closer to the sun, from perihelion distance q [unknown] 0.9 astronomical unit at about A.D. 700 to q [unknown] 0.13 at present (orbital period, 5.25 years), to an expected q [unknown] 0.03 by about 2450; should the comet survive such increasingly close perihelion passages, q will begin steadily to increase shortly thereafter. A review of observations made since discovery is presented, together with a discussion of numerical investigations of the comet's orbit over 4000 years and prospects for observing the upcoming return to perihelion in 1991.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Green, D W -- Rickman, H -- Porter, A C -- Meech, K J -- New York, N.Y. -- Science. 1990 Mar 2;247(4946):1063-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17800064" target="_blank"〉PubMed〈/a〉

Description: Understanding how comets work--what drives their activity--is crucial to the use of comets in studying the early solar system. EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus, taking both images and spectra. Unlike large, relatively inactive nuclei, this nucleus is outgassing primarily because of CO(2), which drags chunks of ice out of the nucleus. It also shows substantial differences in the relative abundance of volatiles from various parts of the nucleus.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉A'Hearn, Michael F -- Belton, Michael J S -- Delamere, W Alan -- Feaga, Lori M -- Hampton, Donald -- Kissel, Jochen -- Klaasen, Kenneth P -- McFadden, Lucy A -- Meech, Karen J -- Melosh, H Jay -- Schultz, Peter H -- Sunshine, Jessica M -- Thomas, Peter C -- Veverka, Joseph -- Wellnitz, Dennis D -- Yeomans, Donald K -- Besse, Sebastien -- Bodewits, Dennis -- Bowling, Timothy J -- Carcich, Brian T -- Collins, Steven M -- Farnham, Tony L -- Groussin, Olivier -- Hermalyn, Brendan -- Kelley, Michael S -- Li, Jian-Yang -- Lindler, Don J -- Lisse, Carey M -- McLaughlin, Stephanie A -- Merlin, Frederic -- Protopapa, Silvia -- Richardson, James E -- Williams, Jade L -- New York, N.Y. -- Science. 2011 Jun 17;332(6036):1396-400. doi: 10.1126/science.1204054.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, University of Maryland, College Park, MD 20742-2421 USA. ma@astro.umd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21680835" target="_blank"〉PubMed〈/a〉

Description: Deep Impact collided with comet Tempel 1, excavating a crater controlled by gravity. The comet's outer layer is composed of 1- to 100-micrometer fine particles with negligible strength (〈65 pascals). Local gravitational field and average nucleus density (600 kilograms per cubic meter) are estimated from ejecta fallback. Initial ejecta were hot (〉1000 kelvins). A large increase in organic material occurred during and after the event, with smaller changes in carbon dioxide relative to water. On approach, the spacecraft observed frequent natural outbursts, a mean radius of 3.0 +/- 0.1 kilometers, smooth and rough terrain, scarps, and impact craters. A thermal map indicates a surface in equilibrium with sunlight.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉A'Hearn, M F -- Belton, M J S -- Delamere, W A -- Kissel, J -- Klaasen, K P -- McFadden, L A -- Meech, K J -- Melosh, H J -- Schultz, P H -- Sunshine, J M -- Thomas, P C -- Veverka, J -- Yeomans, D K -- Baca, M W -- Busko, I -- Crockett, C J -- Collins, S M -- Desnoyer, M -- Eberhardy, C A -- Ernst, C M -- Farnham, T L -- Feaga, L -- Groussin, O -- Hampton, D -- Ipatov, S I -- Li, J-Y -- Lindler, D -- Lisse, C M -- Mastrodemos, N -- Owen, W M Jr -- Richardson, J E -- Wellnitz, D D -- White, R L -- New York, N.Y. -- Science. 2005 Oct 14;310(5746):258-64. Epub 2005 Sep 8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉University of Maryland, College Park, MD 20742, USA. ma@astro.umd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16150978" target="_blank"〉PubMed〈/a〉

Description: On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meech, K J -- Ageorges, N -- A'Hearn, M F -- Arpigny, C -- Ates, A -- Aycock, J -- Bagnulo, S -- Bailey, J -- Barber, R -- Barrera, L -- Barrena, R -- Bauer, J M -- Belton, M J S -- Bensch, F -- Bhattacharya, B -- Biver, N -- Blake, G -- Bockelee-Morvan, D -- Boehnhardt, H -- Bonev, B P -- Bonev, T -- Buie, M W -- Burton, M G -- Butner, H M -- Cabanac, R -- Campbell, R -- Campins, H -- Capria, M T -- Carroll, T -- Chaffee, F -- Charnley, S B -- Cleis, R -- Coates, A -- Cochran, A -- Colom, P -- Conrad, A -- Coulson, I M -- Crovisier, J -- deBuizer, J -- Dekany, R -- de Leon, J -- Dello Russo, N -- Delsanti, A -- DiSanti, M -- Drummond, J -- Dundon, L -- Etzel, P B -- Farnham, T L -- Feldman, P -- Fernandez, Y R -- Filipovic, M D -- Fisher, S -- Fitzsimmons, A -- Fong, D -- Fugate, R -- Fujiwara, H -- Fujiyoshi, T -- Furusho, R -- Fuse, T -- Gibb, E -- Groussin, O -- Gulkis, S -- Gurwell, M -- Hadamcik, E -- Hainaut, O -- Harker, D -- Harrington, D -- Harwit, M -- Hasegawa, S -- Hergenrother, C W -- Hirst, P -- Hodapp, K -- Honda, M -- Howell, E S -- Hutsemekers, D -- Iono, D -- Ip, W-H -- Jackson, W -- Jehin, E -- Jiang, Z J -- Jones, G H -- Jones, P A -- Kadono, T -- Kamath, U W -- Kaufl, H U -- Kasuga, T -- Kawakita, H -- Kelley, M S -- Kerber, F -- Kidger, M -- Kinoshita, D -- Knight, M -- Lara, L -- Larson, S M -- Lederer, S -- Lee, C-F -- Levasseur-Regourd, A C -- Li, J Y -- Li, Q-S -- Licandro, J -- Lin, Z-Y -- Lisse, C M -- LoCurto, G -- Lovell, A J -- Lowry, S C -- Lyke, J -- Lynch, D -- Ma, J -- Magee-Sauer, K -- Maheswar, G -- Manfroid, J -- Marco, O -- Martin, P -- Melnick, G -- Miller, S -- Miyata, T -- Moriarty-Schieven, G H -- Moskovitz, N -- Mueller, B E A -- Mumma, M J -- Muneer, S -- Neufeld, D A -- Ootsubo, T -- Osip, D -- Pandea, S K -- Pantin, E -- Paterno-Mahler, R -- Patten, B -- Penprase, B E -- Peck, A -- Petitas, G -- Pinilla-Alonso, N -- Pittichova, J -- Pompei, E -- Prabhu, T P -- Qi, C -- Rao, R -- Rauer, H -- Reitsema, H -- Rodgers, S D -- Rodriguez, P -- Ruane, R -- Ruch, G -- Rujopakarn, W -- Sahu, D K -- Sako, S -- Sakon, I -- Samarasinha, N -- Sarkissian, J M -- Saviane, I -- Schirmer, M -- Schultz, P -- Schulz, R -- Seitzer, P -- Sekiguchi, T -- Selman, F -- Serra-Ricart, M -- Sharp, R -- Snell, R L -- Snodgrass, C -- Stallard, T -- Stecklein, G -- Sterken, C -- Stuwe, J A -- Sugita, S -- Sumner, M -- Suntzeff, N -- Swaters, R -- Takakuwa, S -- Takato, N -- Thomas-Osip, J -- Thompson, E -- Tokunaga, A T -- Tozzi, G P -- Tran, H -- Troy, M -- Trujillo, C -- Van Cleve, J -- Vasundhara, R -- Vazquez, R -- Vilas, F -- Villanueva, G -- von Braun, K -- Vora, P -- Wainscoat, R J -- Walsh, K -- Watanabe, J -- Weaver, H A -- Weaver, W -- Weiler, M -- Weissman, P R -- Welsh, W F -- Wilner, D -- Wolk, S -- Womack, M -- Wooden, D -- Woodney, L M -- Woodward, C -- Wu, Z-Y -- Wu, J-H -- Yamashita, T -- Yang, B -- Yang, Y-B -- Yokogawa, S -- Zook, A C -- Zauderer, A -- Zhao, X -- Zhou, X -- Zucconi, J-M -- New York, N.Y. -- Science. 2005 Oct 14;310(5746):265-9. Epub 2005 Sep 8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, HI 96822, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16150977" target="_blank"〉PubMed〈/a〉

Description: The impact cratering process on a comet is controversial but holds the key for interpreting observations of the Deep Impact collision with comet 9P/Tempel 1. Mid-infrared data from the Cooled Mid-Infrared Camera and Spectrometer (COMICS) of the Subaru Telescope indicate that the large-scale dust plume ejected by the impact contained a large mass (approximately 10(6) kilograms) of dust and formed two wings approximately +/-45 degrees from the symmetric center, both consistent with gravity as the primary control on the impact and its immediate aftermath. The dust distribution in the inner part of the plume, however, is inconsistent with a pure gravity control and implies that evaporation and expansion of volatiles accelerated dust.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sugita, S -- Ootsubo, T -- Kadono, T -- Honda, M -- Sako, S -- Miyata, T -- Sakon, I -- Yamashita, T -- Kawakita, H -- Fujiwara, H -- Fujiyoshi, T -- Takato, N -- Fuse, T -- Watanabe, J -- Furusho, R -- Hasegawa, S -- Kasuga, T -- Sekiguchi, T -- Kinoshita, D -- Meech, K J -- Wooden, D H -- Ip, W H -- A'Hearn, M F -- New York, N.Y. -- Science. 2005 Oct 14;310(5746):274-8. Epub 2005 Sep 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Complexity Science and Engineering, University of Tokyo, Kashiwa, Chiba, Japan. sugita@k.u-tokyo.ac.jp〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16166476" target="_blank"〉PubMed〈/a〉

Description: The Hubble Space Telescope made systematic observations of the split comet P/Shoemaker-Levy 9 (SL9) (P designates a periodic comet) starting in July 1993 and continuing through mid-July 1994 when the fragments plunged into Jupiter's atmosphere. Deconvolutions of Wide Field Planetary Camera images indicate that the diameters of some fragments may have been as large as approximately 2 to 4 kilometers, assuming a geometric albedo of 4 percent, but significantly smaller values (that is, 〈 1 kilometer) cannot be ruled out. Most of the fragments (or nuclei) were embedded in circularly symmetric inner comae from July 1993 until late June 1994, implying that there was continuous, but weak, cometary activity. At least a few nuclei fragmented into separate, condensed objects well after the breakup of the SL9 parent body, which argues against the hypothesis that the SL9 fragments were swarms of debris with no dominant, central bodies. Spectroscopic observations taken on 14 July 1994 showed an outburst in magnesium ion emission that was followed closely by a threefold increase in continuum emission, which may have been caused by the electrostatic charging and subsequent explosion of dust as the comet passed from interplanetary space into the jovian magnetosphere. No OH emission was detected, but the derived upper limit on the H2O production rate of approximately 10(27) molecules per second does not necessarily imply that the object was water-poor.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Weaver, H A -- A'Hearn, M F -- Arpigny, C -- Boice, D C -- Feldman, P D -- Larson, S M -- Lamy, P -- Levy, D H -- Marsden, B G -- Meech, K J -- New York, N.Y. -- Science. 1995 Mar 3;267(5202):1282-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Space Telescope Science Institute, Baltimore, MD 21218.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7871424" target="_blank"〉PubMed〈/a〉

Description: The Hubble Space Telescope observed the fragmented comet P/Shoemaker-Levy 9 (1993e) (P indicates that it is a periodic comet) on 1 July 1993. Approximately 20 individual nuclei and their comae were observed in images taken with the Planetary Camera. After subtraction of the comae light, the 11 brightest nuclei have magnitudes between approximately 23.7 and 24.8. Assuming that the geometric albedo is 0.04, these magnitudes imply that the nuclear diameters are in the range approximately 2.5 to 4.3 kilometers. If the density of each nucleus is 1 gram per cubic centimeter, the total energy deposited by the impact of these 11 nuclei into Jupiter's atmosphere next July will be approximately 4 x 10(30) ergs ( approximately 10(8) megatons of TNT). This latter number should be regarded as an upper limit because the nuclear magnitudes probably contain a small residual coma contribution. The Faint Object Spectrograph was used to search for fluorescence from OH, which is usually an excellent indicator of cometary activity. No OH emission was detected, and this can be translated into an upper limit on the water production rate of approximately 2 x 10(27) molecules per second.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Weaver, H A -- Feldman, P D -- A'hearn, M F -- Arpigny, C -- Brown, R A -- Helin, E F -- Levy, D H -- Marsden, B G -- Meech, K J -- Larson, S M -- Noll, K S -- Scotti, J V -- Sekanina, Z -- Shoemaker, C S -- Shoemaker, E M -- Smith, T E -- Storrs, A D -- Yeomans, D K -- Zellner, B -- New York, N.Y. -- Science. 1994 Feb 11;263(5148):787-91.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17770832" target="_blank"〉PubMed〈/a〉