Search

Your search keyword '"A'Hearn, Michael"' showing total 602 results
Start Over Author "A'Hearn, Michael"
602 results on '"A'Hearn, Michael"'

101. On the formation and evolution of gaseous structures in Comet P/Halley

Author

Schulz, Rita, A'Hearn, Michael F., and Samarasinha, Nalin H.

Subjects
Halley's comet -- Analysis, Astronomy, Earth sciences
Abstract

The CN jets and CN shells present in the coma of the Comet P/Halley are dynamically connected, and can be analyzed by numerical simulations on the spatial and temporal evolution of gaseous jets. The evolution of a gaseous jet into a shell is straightforward for several geometric configuration. The projection effect causes the appearance of a closed shell structure, which indicates that the observational geometry is close to an equator on view, and that the material in shells is from an active area located near the equator of the nucleus.

Published
1993

102. Water vaporization on Ceres

Author

A'Hearn, Michael F. and Feldman, Paul D.

Subjects
Ceres (Asteroid) -- Research, Water vapor, Atmospheric -- Research, Astronomy, Earth sciences
Abstract

The atmosphere of Ceres is considered as an transitional case between the stable atmosphere of major planets and the freely outflowing atmospheres of comets. The emission of hydroxide was used to further characterize the nature of its atmosphere. The southern limb of Ceres exhibited no evidence of hydroxide emission while its northern limb showed significant emissions. The presence of escaping water in Ceres was established.

Published
1992

103. g-factors of the SH (O-O) band and the SH upper limit in Comet P/Brorsen-Metcalf (1980o)

Author

Kim, Sang J. and A'Hearn, Michael F.

Subjects
Comets -- Composition, Astronomical research -- Research, Astronomy, Earth sciences
Abstract

The upper limit of SH and its lifetime is calculated for Comet P/Brorsen-Metcalf. SH is the prime dissociative product of H2S, recently discovered in the microwave range in Levy's and Austin's Comet. The upper limit production rate is Q(SH)/Q(H2O) < 0.017. Lifetime of SH is 105 sec at 1 AU for v(r) = -28.5 km/sec. SH temperature is calculated to be 150 to 400 K. Discussions of other models and studies are presented.

Published
1992

106. Detection of CN emission from (2060) Chiron

Author

Bus, Schelte J., A'Hearn, Michael F., Schleicher, David G., and Bowell, Edward

Subjects
Asteroids -- Research -- Spectra, Cyanides -- Research, Comets -- Spectra -- Research, Chiron (Comet) -- Research -- Spectra, Science and technology, Research, Spectra
Abstract

THE UNUSUAL NATURE OF (2060) Chiron has become increasingly apparent since Kowal's discovery of the object in 1977 [1]. In spite of Chiron's large heliocentric distance and unstable orbit [2], [...]

Published
1991

107. Stellar Occultation by Comet 67P/Churyumov–Gerasimenko Observed with Rosetta's Alice Far-ultraviolet Spectrograph

Author

Keeney, Brian A., primary, Stern, S. Alan, additional, Feldman, Paul D., additional, A’Hearn, Michael F., additional, Bertaux, Jean-Loup, additional, Feaga, Lori M., additional, Knight, Matthew M., additional, Medina, Richard A., additional, Noonan, John, additional, Parker, Joel Wm., additional, Pineau, Jon P., additional, Schindhelm, Rebecca N., additional, Steffl, Andrew J., additional, Versteeg, M., additional, Vervack, Ronald J., additional, and Weaver, Harold A., additional

Published
2019
Full Text
View/download PDF

109. g-factors of the SH (0-0) band and SH upper limit in Comet P/Brorsen-Metcalf (1989o)

Author

Kim, Sang J and A'Hearn, Michael F

Subjects
Astrophysics
Abstract

A search for SH, the prime dissociative product of H2S, has been prompted by the microwave-band detection of H2S in Comets Austin and Levy. Attention is accordingly given here to g-factors for the A-X (0-0) band of SH as a function of heliocentric velocity at a heliocentric distance of 1 AU. An upper-limit production rate for SH relative to water of 0.017 is derived for the case of Comet P/Brorsen-Metcalf. A dissociative lifetime of 105 sec, at 1 AU heliocentric distance, and a heliocentric velocity of -28.5 km/sec, are also obtained.

Published
1992
Full Text
View/download PDF

110. CN jet velocity in Comet P/Halley

Author

Klavetter, James J and A'Hearn, Michael F

Subjects
Astrophysics
Abstract

The projected expansion velocity of Comet Halley's coma is presently determined in CN jet images that were processed with a radial profile subtraction technique. It is established that the flow is approximately radial, and that the velocity can also be determined by measuring specific radial features in jets. The largest projected velocity is 1.7 +/- 0.3 km/sec, at 50,000 km from the nucleus. This is the largest expansion velocity found for this region of the Comet Halley coma. Comparisons are made with other observations and theoretical models.

Published
1992
Full Text
View/download PDF

113. Observational and dynamical constraints on the rotation of Comet P/Halley

Author

Samarasinha, Nalin H and A'Hearn, Michael F

Subjects
Astrophysics
Abstract

The present search for all rotational states of the P/Halley nucleus which can explain a broad spectrum of observational data notes that the orientation of the long-axis large end of the comet during its encounter with Vega-1 must be reversed from that proposed by Sagdeev et al. (1989). In the modes identified as most likely for the rotational state, the long axis conducts a 3.7-day precessional motion around the space-fixed vector of total rotational angular momentum, while rotating around itself with a 7.3-day period.

Published
1991
Full Text
View/download PDF

114. Upper Limits of SO AND SO2 in Comets

Author

Kim, Sang J and A'Hearn, Michael F

Subjects
Astrophysics
Abstract

We have calculated synthetic spectra of SO and compared them with spectra of Comets I-A-A and P/Halley, in which Wallis and Krishna-Swamy claimed a tentative identification of SO. We found no evidence for the presence of So in these spectra. The derived upper limits on the production rates of SO and S02 in Comet I-A-A were found to be at least 50 times less than the S2 production rate. We also found that the SO and S02 upper limits in Comets P/Halley, P/Encke, and Bradfield (1979X) were less than the S2 abundance, reported in Comet IRAS-Araki-Alcock. Our result, contradict recent irradiation experiments, which produced abundant SO compared with S2 under most circumstances. This may suggest totally different models of the S2 producing mechanism in comets.

Published
1991
Full Text
View/download PDF

115. Special Report: Chemistry of Comets.

Author

A'Hearn, Michael F.

Abstract

Discusses the chemistry of comets. How comets provide clues to the birth of the solar system, photolytic reactions on comets involving water, chemical modeling, nuclear chemistry, and research findings are among the areas considered. (JN)

Published
1984

116. Standard stars for photometry of comets

Author

Osborn, Wayne H, A'Hearn, Michael F, Carsenty, Uri, Millis, Robert L, and Schleicher, David G

Subjects
Astronomy
Abstract

Magnitudes are presented in 10 bandpasses for 63 stars that can be used as standards in photometric observations of comets. The bandpasses are, in addition to those for three (UV, blue, and red) continuum points, those which measure C2, C3, CN, CO(+), H2O(+), OH, and NH emissions. After correction for extinction, the derived magnitudes were transformed to a zero point such that all filters showed magnitude 5.88 for the star HD 3379. The internal agreement among the present observations and the agreement obtained between the observations and independently published measures indicate that the derived magnitudes are generally accurate to + or - 0.01 mag.

Published
1990
Full Text
View/download PDF

117. Ultraviolet Observations of Coronal Mass Ejection Impact on Comet 67P/Churyumov–Gerasimenko by Rosetta Alice

Author

Noonan, John W., primary, Stern, S. Alan, additional, Feldman, Paul D., additional, Broiles, Thomas, additional, Wedlund, Cyril Simon, additional, Edberg, Niklas J. T., additional, Schindhelm, Rebecca N., additional, Parker, Joel Wm., additional, Keeney, Brian A., additional, Vervack Jr, Ronald J., additional, Steffl, Andrew J., additional, Knight, Matthew M., additional, Weaver, Harold A., additional, Feaga, Lori M., additional, A’Hearn, Michael, additional, and Bertaux, Jean-Loup, additional

Published
2018
Full Text
View/download PDF

122. FUV Spectral Signatures of Molecules and the Evolution of the Gaseous Coma of Comet 67P/Churyumov–Gerasimenko

Author

Feldman, Paul D., primary, A’Hearn, Michael F., additional, Bertaux, Jean-Loup, additional, Feaga, Lori M., additional, Keeney, Brian A., additional, Knight, Matthew M., additional, Noonan, John, additional, Parker, Joel Wm., additional, Schindhelm, Rebecca N., additional, Steffl, Andrew J., additional, Stern, S. Alan, additional, Vervack, Ronald J., additional, and Weaver, Harold A., additional

Published
2017
Full Text
View/download PDF

133. H2O and O2 absorption in the coma of comet 67P/Churyumov–Gerasimenko measured by the Alice far-ultraviolet spectrograph on Rosetta

Author

Keeney, Brian A., primary, Stern, S. Alan, additional, A’Hearn, Michael F., additional, Bertaux, Jean-Loup, additional, Feaga, Lori M., additional, Feldman, Paul D., additional, Medina, Richard A., additional, Parker, Joel Wm., additional, Pineau, Jon P., additional, Schindhelm, Eric, additional, Steffl, Andrew J., additional, Versteeg, M., additional, and Weaver, Harold A., additional

Published
2017
Full Text
View/download PDF

136. Unanticipated Physical Processes in ALICE Spectra of 67P/Churyumov-Gerasimenko

Author

A'Hearn, Michael F., Bertaux, Jean-Loup, Feaga, Lori M., Feldman, Paul D., Parker, Joel Wm., Schindhelm, Eric R., Steffl, Andrew J., Stern, S. Alan, Weaver, Harold A., Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Johns Hopkins University (JHU), Department of Space Studies [Boulder], Southwest Research Institute [Boulder] (SwRI), Johns Hopkins University Applied Physics Laboratory [Laurel, MD] (APL), and Cardon, Catherine

Subjects
[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], [SDU.ASTR.EP] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
Abstract

International audience; FUV spectra of comet 67P by the ALICE instrument on Rosetta show atomic emission-line ratios (of C, O, and H) that are very different from those seen in comets near the sun. These line ratios suggest that they are formed largely by prompt emission after electron impact dissociation of parent molecules rather than photo-dissociation, but other processes may also be involved. The primary molecules leading to these atomic emissions are likely H2O, CO2, CO, and O2, of which we only directly measure CO. As prompt emission, the atomic lines trace the column density of the parents. The CO is directly detected only in a small subset of our data, primarily over the southern limb, whereas most of our data at the time of writing are over the northern limb.We will present constraints on the relative column densities from the line ratios and compare with column densities of CO and with results for other molecules as measured with other instruments on Rosetta. We expect that these results will change significantly by the autumnal equinox in mid-July when the now barely illuminated southern hemisphere enters its summer. We will also present our results on the FUV spectroscopy of the surface at selected locations and consider whether there are surface variations that might be correlated with the outgassing variations.

Published
2015

137. Rotational Variation of Outgassing Morphology in 67P/Churyumov-Gerasimenko

Author

A'Hearn, Michael F., Bodewits, Dennis, La Forgia, Fiorangela, Lara, Luisa M., Agarwal, Jessica, Bertaux, Jean-Loup, Cremonese, Gabriele, Davidsson, Björn, Fornasier, Sonia, Güttler, Carsten, Knollenberg, Jorg, Lazzarin, Monica, Leyrat, Cedric, Lin, Zhong-Yi, Magrin, Sara, Naletto, Giampiero, Sierks, Holger, Snodgrass, Colin, Thomas, Nicolas, Tubiana, Cecilia, Vincent, Jean-Baptiste, Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Dipartimento di Fisica e Astronomia 'Galileo Galilei', Universita degli Studi di Padova, Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Padova (OAPD), Istituto Nazionale di Astrofisica (INAF), Department of Physics and Astronomy [Uppsala], Uppsala University, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), DLR Institute of Planetary Research, German Aerospace Center (DLR), Institute of Astronomy [Taiwan] (IANCU), National Central University [Taiwan] (NCU), Department of Industrial Engineering [Padova], Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), The Open University [Milton Keynes] (OU), Universität Bern [Bern], Università degli Studi di Padova = University of Padua (Unipd), Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research (MPS), and Universität Bern [Bern] (UNIBE)

Subjects
[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], Astrophysics::Earth and Planetary Astrophysics
Abstract

International audience; Images of the innermost coma of comet 67P/Churyumov-Gerasimenko taken in various gaseous species with the OSIRIS camera on Rosetta show localized sources that expand hemispherically, contrary to the narrow jets seen in broad band images, which are domnated by continuum radiation reflected by the grains. The gaseous images have the continuum removed, but we have not derived column densities because of uncertainty about physical processes. Thus the morphology is the most reliable aspect of the data. We will compare the morphology in various species and attempt to estimate the decoupling distance of the grains from the gas. We will also attempt to relate these features to the point of origin on the nucleus.

Published
2015

139. Gas outflow and dust transport of comet 67P/Churyumov–Gerasimenko

Author

Lai, Ian-Lin, primary, Ip, Wing-Huen, additional, Su, Cheng-Chin, additional, Wu, Jong-Shinn, additional, Lee, Jui-Chi, additional, Lin, Zhong-Yi, additional, Liao, Ying, additional, Thomas, Nicolas, additional, Sierks, Holger, additional, Barbieri, Cesare, additional, Lamy, Philippe, additional, Rodrigo, Rafael, additional, Koschny, Detlef, additional, Rickman, Hans, additional, Keller, Horst Uwe, additional, Agarwal, Jessica, additional, A’Hearn, Michael F., additional, Barucci, Maria Antonella, additional, Bertaux, Jean-Loup, additional, Bertini, Ivano, additional, Boudreault, Steven, additional, Cremonese, Gabriele, additional, Da Deppo, Vania, additional, Davidsson, Björn, additional, Debei, Stefano, additional, De Cecco, Mariolino, additional, Deller, Jakob, additional, Fornasier, Sonia, additional, Fulle, Marco, additional, Groussin, Olivier, additional, Gutiérrez, Pedro J., additional, Güttler, Carsten, additional, Hofmann, Marc, additional, Hviid, Stubbe F., additional, Jorda, Laurent, additional, Knollenberg, Jörg, additional, Kovacs, Gabor, additional, Kramm, J.-Rainer, additional, Kührt, Ekkehard, additional, Küppers, Michael, additional, Lara, Luisa M., additional, Lazzarin, Monica, additional, Lopez Moreno, Josè J., additional, Marzari, Francesco, additional, Naletto, Giampiero, additional, Oklay, Nilda, additional, Shi, Xian, additional, Tubiana, Cecilia, additional, and Vincent, Jean-Baptiste, additional

Published
2016
Full Text
View/download PDF

140. Geomorphological mapping of comet 67P/Churyumov–Gerasimenko’s Southern hemisphere

Author

Lee, Jui-Chi, primary, Massironi, Matteo, additional, Ip, Wing-Huen, additional, Giacomini, Lorenza, additional, Ferrari, Sabrina, additional, Penasa, Luca, additional, El-Maarry, Mohamed Ramy, additional, Pajola, Maurizio, additional, Lai, Ian-Lin, additional, Lin, Zhong-Yi, additional, Ferri, Francesca, additional, Sierks, Holger, additional, Barbieri, Cesare, additional, Lamy, Philippe, additional, Rodrigo, Rafael, additional, Koschny, Detlef, additional, Rickman, Hans, additional, Keller, Horst Uwe, additional, Agarwal, Jessica, additional, A’Hearn, Michael F., additional, Barucci, Maria Antonella, additional, Bertaux, Jean-Loup, additional, Bertini, Ivano, additional, Cremonese, Gabriele, additional, Da Deppo, Vania, additional, Davidsson, Björn, additional, Debei, Stefano, additional, De Cecco, Mariolino, additional, Deller, Jakob, additional, Fornasier, Sonia, additional, Fulle, Marco, additional, Groussin, Olivier, additional, Gutiérrez, Pedro J., additional, Güttler, Carsten, additional, Hofmann, Marc, additional, Hviid, Stubbe F., additional, Jorda, Laurent, additional, Knollenberg, Jörg, additional, Kovacs, Gabor, additional, Kramm, J.-Rainer, additional, Kührt, Ekkehard, additional, Küppers, Michael, additional, Lara, Luisa M., additional, Lazzarin, Monica, additional, Marzari, Francesco, additional, Lopez Moreno, Josè J., additional, Naletto, Giampiero, additional, Oklay, Nilda, additional, Shi, Xian, additional, Thomas, Nicolas, additional, Tubiana, Cecilia, additional, and Vincent, Jean-Baptiste, additional

Published
2016
Full Text
View/download PDF

141. 67P/Churyumov-Gerasimenko: Activity between March and June 2014 as observed from Rosetta/OSIRIS

Author

Tubiana, C., Snodgrass, C., Bertini, I., Mottola, S., Vincent, J.-B., Lara, L., Fornasier, S., Knollenberg, J., Thomas, N., Fulle, M., Agarwal, J., Bodewits, Dennis, Ferri, F., Güttler, C., Gutierrez, P. J., La Forgia, F., Lowry, S., Magrin, S., Oklay, N., Pajola, M., Rodrigo, R., Sierks, H., A'Hearn, Michael F., Angrilli, F., Barbieri, C., Barucci, M. A., Bertaux, Jean-Loup, Cremonese, Gabriele, Da Deppo, V., Davidsson, B., De Cecco, M., Debei, S., Groussin, O., Hviid, S. F., Ip, W., Jorda, L., Keller, H. U., Koschny, D., Kramm, R., Kührt, Ekkehard, Küppers, M., Lazzarin, M., Lamy, P. L., Lopez Moreno, J. J., Marzari, F., Michalik, H., Naletto, G., Rickman, H., Sabau, L., Wenzel, K.-P., Max-Planck-Institut für Sonnensystemforschung (MPS), Max-Planck-Gesellschaft, School of Physical Sciences [Milton Keynes], Faculty of Science, Technology, Engineering and Mathematics [Milton Keynes], The Open University [Milton Keynes] (OU)-The Open University [Milton Keynes] (OU), Centro di Ateneo di Studi e Attività Spaziali 'Giuseppe Colombo' (CISAS), Universita degli Studi di Padova, DLR Institute of Planetary Research, German Aerospace Center (DLR), Instituto de Astrofísica de Andalucía (IAA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Physikalisches Institut [Bern], Universität Bern [Bern], INAF - Osservatorio Astronomico di Trieste (OAT), Istituto Nazionale di Astrofisica (INAF), Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Dipartimento di Fisica e Astronomia 'Galileo Galilei', Centre for Astrophysics and Planetary Science [Canterbury] (CAPS), University of Kent [Canterbury], International Space Science Institute [Bern] (ISSI), Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), PLANETO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astronomico di Padova (OAPD), Department of Physics and Astronomy [Uppsala], Uppsala University, Università degli Studi di Trento (UNITN), Department of Industrial Engineering [Padova], Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institute of Space Science [Taiwan], National Central University [Taiwan] (NCU), Institut für Geophysik und Extraterrestrische Physik [Braunschweig] (IGEP), Technische Universität Braunschweig = Technical University of Braunschweig [Braunschweig], Research and Scientific Support Department, ESTEC (RSSD), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA)-European Space Agency (ESA), European Space Astronomy Centre (ESAC), European Space Agency (ESA), Dipartimento di Fisica [Padova], Institut für Datentechnik und Kommunikationsnetze, Department of Information Engineering [Padova] (DEI), and Instituto Nacional de Técnica Aeroespacial (INTA)

Subjects
[SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP]
Abstract

International audience; 67P/Churyumov-Gerasimenko is the target comet of the ESA’s Rosetta mission. After commissioning at the end of March 2014, the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) onboard Rosetta, started imaging the comet and its dust environment to investigate how they change and evolve while approaching the Sun.Methods. We focused our work on Narrow Angle Camera (NAC) orange images and Wide Angle Camera (WAC) red and visible-610 images acquired between 2014 March 23 and June 24 when the nucleus of 67P was unresolved and moving from approximately 4.3 AU to 3.8 AU inbound. During this period the 67P – Rosetta distance decreased from 5 million to 120 thousand km.Results. Through aperture photometry, we investigated how the comet brightness varies with heliocentric distance. 67P was likely already weakly active at the end of March 2014, with excess flux above that expected for the nucleus. The comet’s brightness was mostly constant during the three months of approach observations, apart from one outburst that occurred around April 30 and a second increase in flux after June 20. Coma was resolved in the profiles from mid-April. Analysis of the coma morphology suggests that most of the activity comes from a source towards the celestial north pole of the comet, but the outburst that occurred on April 30 released material in a different direction.

Published
2015

143. Comets keys to the solar system's past: after four successful missions to study comets up close, astronomers find answers to the biggest questions about the solar system's origins

Author

A'Hearn, Michael F.

Subjects
Comets -- Natural history -- Observations -- Spectra -- Structure, Astronomy
Abstract

Comets can be tricky. Occasionally--perhaps every 10 years or so--one becomes the most spectacular phenomenon in the nighttime sky. This makes them an object of popular fascination and has led [...]

Published
2011

144. Shape shifters

Author

A'Hearn, Michael

Subjects
Comets -- Natural history -- Spectra -- Properties, Astronomy
Abstract

Q: Photos of recent comet flybys show their nuclei to be barbell-shaped rather than spherical. What are the forces or processes that produce this shape? --Nathan Fawcett, Ithaca, New York [...]

Published
2011

146. Aswan site on comet 67P/Churyumov-Gerasimenko: Morphology, boulder evolution, and spectrophotometry

Author

Pajola, Maurizio, primary, Oklay, Nilda, additional, La Forgia, Fiorangela, additional, Giacomini, Lorenza, additional, Massironi, Matteo, additional, Bertini, Ivano, additional, El-Maarry, M. R., additional, Marzari, Francesco, additional, Preusker, Frank, additional, Scholten, Frank, additional, Höfner, Sebastian, additional, Lee, Jui-Chi, additional, Vincent, Jean-Baptiste, additional, Groussin, Olivier, additional, Naletto, Giampiero, additional, Lazzarin, Monica, additional, Barbieri, Cesare, additional, Sierks, Holger, additional, Lamy, Philippe, additional, Rodrigo, Rafael, additional, Koschny, Detlef, additional, Rickman, Hans, additional, Keller, Horst U., additional, Agarwal, Jessica, additional, A’Hearn, Michael F., additional, Barucci, Maria A., additional, Bertaux, Jean-Loup, additional, Cremonese, Gabriele, additional, Deppo, Vania Da, additional, Davidsson, Björn, additional, De Cecco, Mariolino, additional, Debei, Stefano, additional, Ferri, Francesca, additional, Fornasier, Sonia, additional, Fulle, Marco, additional, Güttler, Carsten, additional, Gutierrez, Pedro J., additional, Hviid, Stubbe F., additional, Ip, Wing-Huen, additional, Jorda, Laurent, additional, Knollenberg, Jörg, additional, Kramm, J.-Rainer, additional, Küppers, Michael, additional, Kürt, Ekkehard, additional, Lara, Luisa M., additional, Lin, Zhong-Yi, additional, Lopez Moreno, Jose J., additional, Magrin, Sara, additional, Michalik, Harald, additional, Mottola, Stefano, additional, Thomas, Nicholas, additional, and Tubiana, Cecilia, additional

Published
2016
Full Text
View/download PDF

147. The southern hemisphere of 67P/Churyumov-Gerasimenko: Analysis of the preperihelion size-frequency distribution of boulders ≥7 m

Author

Pajola, Maurizio, primary, Lucchetti, Alice, additional, Vincent, Jean-Baptiste, additional, Oklay, Nilda, additional, El-Maarry, Mohamed R., additional, Bertini, Ivano, additional, Naletto, Giampiero, additional, Lazzarin, Monica, additional, Massironi, Matteo, additional, Sierks, Holger, additional, Barbieri, Cesare, additional, Lamy, Philippe, additional, Rodrigo, Rafael, additional, Koschny, Detlef, additional, Rickman, Hans, additional, Keller, Horst U., additional, Agarwal, Jessica, additional, A’Hearn, Michael F., additional, Barucci, Maria A., additional, Bertaux, Jean-Loup, additional, Boudreault, Steve, additional, Cremonese, Gabriele, additional, Deppo, Vania Da, additional, Davidsson, Björn, additional, Debei, Stefano, additional, De Cecco, Mariolino, additional, Deller, Jakob, additional, Fornasier, Sonia, additional, Fulle, Marco, additional, Gicquel, Adeline, additional, Groussin, Olivier, additional, Gutierrez, Pedro J., additional, Güttler, Carsten, additional, Hofmann, Marc, additional, Höfner, Sebastian, additional, Hviid, Stubbe F., additional, Ip, Wing-Huen, additional, Jorda, Laurent, additional, Knollenberg, Jörg, additional, Kramm, J.-Rainer, additional, Kührt, Ekkehard, additional, Küppers, Michael, additional, La Forgia, Fiorangela, additional, Lara, Luisa M., additional, Lee, Jui-Chi, additional, Lin, Zhong-Yi, additional, Lopez Moreno, Jose J., additional, Marzari, Francesco, additional, Michalik, Harald, additional, Mottola, Stefano, additional, Preusker, Frank, additional, Scholten, Frank, additional, Thomas, Nicholas, additional, Toth, Imre, additional, and Tubiana, Cecilia, additional

Published
2016
Full Text
View/download PDF

148. THE NATURE AND FREQUENCY OF THE GAS OUTBURSTS IN COMET 67P/CHURYUMOV–GERASIMENKO OBSERVED BY THE ALICE FAR-ULTRAVIOLET SPECTROGRAPH ON ROSETTA

Author

Feldman, Paul D., primary, A’Hearn, Michael F., additional, Feaga, Lori M., additional, Bertaux, Jean-Loup, additional, Noonan, John, additional, Parker, Joel Wm., additional, Schindhelm, Rebecca N., additional, Steffl, Andrew J., additional, Stern, S. Alan, additional, and Weaver, Harold A., additional

Published
2016
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results