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Jean-loup Bertaux - One of the best experts on this subject based on the ideXlab platform.
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Water Production Rate of C/2020 F3 (NEOWISE) from SOHO/SWAN over Its Active Apparition
The Astrophysical journal letters, 2021Co-Authors: Michael R Combi, Jean-loup Bertaux, Eric Quémerais, J. Teemu T. Mäkinen, Stéphane FerronAbstract:C/2020 F3 (NEOWISE) was discovered in images from the Near Earth Object program of the Wide-Field Infrared Survey Explorer (NEOWISE) taken on 2020 March 27 and has become the Great Comet of 2020. The Solar Wind ANisotropies (SWAN) camera on the Solar and Heliospheric Observatory (SOHO) spacecraft, located in a halo orbit around the Earth–Sun L1 Lagrange point, makes daily full-sky images of hydrogen Lyα. Water production rates were determined from the SWAN hydrogen Lyα brightness and spatial distribution of the comet measured over a 4 month period of time on either side of the comet's Perihelion on 2020 July 3. The water production rate in s−1 was moderately asymmetric around Perihelion and varied with the heliocentric distance, r, in au as (6.9 ± 0.5) × 1028 r −2.5±0.2 and (10.1 ± 0.5) × 1028 r −3.5±0.1 before and after Perihelion, respectively. This is consistent with the comet having been through the planetary region of the solar system on one or more previous apparitions. Water production rates as large as 5.27 × 1030 s−1 were determined shortly after Perihelion, once the comet was outside the solar avoidance area of SWAN, when the comet was 0.324 au from the Sun.
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Seasonal Changes In Hydrogen Escape From Mars through Analysis of HST Observations of the Martian Exosphere Near Perihelion
Journal of Geophysical Research Space Physics, 2017Co-Authors: D. Bhattacharyya, Jean-loup Bertaux, J. T. Clarke, Jean-yves Chaufray, M. Mayyasi, M. S. Chaffin, N. M. Schneider, G. L. VillanuevaAbstract:Hubble Space Telescope (HST) observations of the Martian hydrogen exosphere in Lyman α are presented in this paper for a period when Mars passed Perihelion and southern summer solstice in its orbit. The peak intensity in the exospheric Lyman α brightness was recorded after Mars went past its Perihelion, slightly after southern summer solstice. The increase in brightness as Mars approached Perihelion was found to not be symmetric around the peak, making it impossible to fit the H escape flux trend with a single sinusoidal curve with the peak at Perihelion. While the short-term (~30 Earth-days) changes were not directly correlated with changes in the solar Lyman α flux, the long-term (~ 10 Earth-years) trend in the data does show some correlation with solar activity. This suggests that the short-term changes brought about in the exosphere could be due to intrinsic changes occurring within the lower atmosphere. For example, thermospheric heating by dust can alter the cold-trapping mechanism for water vapor resulting in it being present in large quantities at higher altitudes (60-80 km), possibly enhancing the escape flux of H. Therefore, it is important to understand the drivers of atmospheric dynamics in the Martian atmosphere, which produce the yearly-enhanced seasonal changes observed at Mars around periapsis and southern summer solstice in order to accurately determine the total amount of water lost over its history.
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estimate of the erosion rate from h 2 o mass loss measurements from swan soho in previous Perihelions of comet 67p churyumov gerasimenko and connection with observed rotation rate variations
Astronomy and Astrophysics, 2015Co-Authors: Jean-loup BertauxAbstract:The SWAN Lyman α photometer onboard SOHO monitored the hydrogen cloud around comet 67P/Churyumov- Gerasimenko (67P) post Perihelion at the three last Perihelions in 1996, 2002, and 2009. The Rosetta instruments are collecting a wealth of new data during the satellite rendezvous with this comet. Aims. Combining the SWAN results with some new Rosetta data allows estimating the erosion rate of the comet at each orbit. Methods. By integrating the production rates measured with SWAN in time and adding some estimates for periods that are not covered by SWAN measurements, we estimate the total H 2 O mass loss per orbit to be 2.7± 0.4x10 9 kg. It is possible to measure the erosion rate more accurately with the precise knowledge of the area of the nucleus (47.4 km 2 ), the outgassing rates, and dust-to- gas mass ratios (4±2) determined from Rosetta instruments, along with the mean density of the nucleus. The erosion rate is quantified by the thickness of a layer that is disposed of at each orbit, mainly around Perihelion. We also tried to explain the observed change in the rotation rate during the 2009 orbit (a decrease in the period of 1285 s) and the change observed by Rosetta from June 2014 to February 2015 (increase in the period of 32 s and 98 s up to 17 May 2015) with three different mechanisms: sublimation-induced torque, thermal dilatation, and separation between the two lobes. With a dust-to gas mass ratio of 2, the estimated layer is between 0.5 to 0.6 m thick, while it reaches 1.0 to 1.4 m for a dust-to gas mass ratio of 6. This means that a layer of 1.0 ±0.5 m thickness is lost at each orbit. The outgassing-induced torque may explain the observed changes in the rotation rate around Perihelion in 2009 and recent changes. We argue that dilatation and separation of lobes cannot explain the Perihelion change in 2009 (increase) because these mechanisms would either let the rotation remain unchanged or would decrease the rotation rate. These mechanisms are quantified and cannot be totally excluded for the observed changes from June 2014 to February 2015. They would need to become three times larger to explain the 98 s change in period up to 17 May, which is somewhat unrealistic. Our preferred scheme is the sublimation-induced torque, which our computations show to be fully compatible with the known outgassing rates. The torque decelerated the rotation from August 2014 to 17 May 2015, at which time it changed sign and began to accelerate the rotation, consistent with the average behavior observed for the 2009 apparition. The thickness of lost material needs to be kept in mind when interpreting all surface features. It probably rules out the existence of a ubiquitous crust mantle that would survive many orbits. At 1 m ± 0.5 m, the erosion rate per orbit is high and supports the idea that the composition of the material that is measured in the coma (gas and solid) is indeed representative of the bulk material of the nucleus. We also argued that monitoring the rotation rate yields a very accurate and precious indicator of the global activity of the comet with which other activity measurements can be compared.
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Estimate of the erosion rate from H2O mass-loss measurements from SWAN/SOHO in previous Perihelions of comet 67P/Churyumov-Gerasimenko and connection with observed rotation rate variations
Astronomy and Astrophysics - A&A, 2015Co-Authors: Jean-loup BertauxAbstract:The SWAN Lyman α photometer onboard SOHO monitored the hydrogen cloud around comet 67P/Churyumov- Gerasimenko (67P) post Perihelion at the three last Perihelions in 1996, 2002, and 2009. The Rosetta instruments are collecting a wealth of new data during the satellite rendezvous with this comet. Aims. Combining the SWAN results with some new Rosetta data allows estimating the erosion rate of the comet at each orbit. Methods. By integrating the production rates measured with SWAN in time and adding some estimates for periods that are not covered by SWAN measurements, we estimate the total H2O mass loss per orbit to be 2.7± 0.4x109 kg. It is possible to measure the erosion rate more accurately with the precise knowledge of the area of the nucleus (47.4 km2), the outgassing rates, and dust-to- gas mass ratios (4±2) determined from Rosetta instruments, along with the mean density of the nucleus. The erosion rate is quantified by the thickness of a layer that is disposed of at each orbit, mainly around Perihelion. We also tried to explain the observed change in the rotation rate during the 2009 orbit (a decrease in the period of 1285 s) and the change observed by Rosetta from June 2014 to February 2015 (increase in the period of 32 s and 98 s up to 17 May 2015) with three different mechanisms: sublimation-induced torque, thermal dilatation, and separation between the two lobes. With a dust-to gas mass ratio of 2, the estimated layer is between 0.5 to 0.6 m thick, while it reaches 1.0 to 1.4 m for a dust-to gas mass ratio of 6. This means that a layer of 1.0 ±0.5 m thickness is lost at each orbit. The outgassing-induced torque may explain the observed changes in the rotation rate around Perihelion in 2009 and recent changes. We argue that dilatation and separation of lobes cannot explain the Perihelion change in 2009 (increase) because these mechanisms would either let the rotation remain unchanged or would decrease the rotation rate. These mechanisms are quantified and cannot be totally excluded for the observed changes from June 2014 to February 2015. They would need to become three times larger to explain the 98 s change in period up to 17 May, which is somewhat unrealistic. Our preferred scheme is the sublimation-induced torque, which our computations show to be fully compatible with the known outgassing rates. The torque decelerated the rotation from August 2014 to 17 May 2015, at which time it changed sign and began to accelerate the rotation, consistent with the average behavior observed for the 2009 apparition. The thickness of lost material needs to be kept in mind when interpreting all surface features. It probably rules out the existence of a ubiquitous crust mantle that would survive many orbits. At 1 m ± 0.5 m, the erosion rate per orbit is high and supports the idea that the composition of the material that is measured in the coma (gas and solid) is indeed representative of the bulk material of the nucleus. We also argued that monitoring the rotation rate yields a very accurate and precious indicator of the global activity of the comet with which other activity measurements can be compared.
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Unusual Water Production Activity of Comet C/2012 S1 (ISON): Outbursts and Continuous Fragmentation
The Astrophysical journal letters, 2014Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, N. Fougere, Stéphane FerronAbstract:The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyα camera on the SOlar and Heliospheric Observer (SOHO) satellite observed the hydrogen coma of comet C/2012 S1 (ISON) for most of the last month of its activity from 2013 October 24 to November 24, ending just 4 days before Perihelion and its final disruption. The water production rate of the comet was determined from these observations. SOHO has been operating in a halo orbit around the Earth-Sun L1 Lagrange point since its launch in late 1995. Most water vapor produced by comets is ultimately photodissociated into two H atoms and one O atom producing a huge hydrogen coma that is routinely observed in the daily SWAN images in comets of sufficient brightness. Water production rates were calculated from 22 images over most of the last month of the pre-Perihelion apparition. The water production rate increased very slowly on average from October 24.9 until November 12.9, staying between 1.8 and 3.4 × 1028 s-1, after which it increased dramatically, reaching 1.6 to 2 × 1030 s-1 from November 21.6 to 23.6. It was not detected after Perihelion on December 3.7 when it should have been visible. We examine the active surface area necessary to explain the water production rate and its variation and are able to place constraints on the physical size of the original nucleus necessary to account for the large amount of activity from November 12.9 and until just before Perihelion.
Eric Quémerais - One of the best experts on this subject based on the ideXlab platform.
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Water Production Rate of C/2020 F3 (NEOWISE) from SOHO/SWAN over Its Active Apparition
The Astrophysical journal letters, 2021Co-Authors: Michael R Combi, Jean-loup Bertaux, Eric Quémerais, J. Teemu T. Mäkinen, Stéphane FerronAbstract:C/2020 F3 (NEOWISE) was discovered in images from the Near Earth Object program of the Wide-Field Infrared Survey Explorer (NEOWISE) taken on 2020 March 27 and has become the Great Comet of 2020. The Solar Wind ANisotropies (SWAN) camera on the Solar and Heliospheric Observatory (SOHO) spacecraft, located in a halo orbit around the Earth–Sun L1 Lagrange point, makes daily full-sky images of hydrogen Lyα. Water production rates were determined from the SWAN hydrogen Lyα brightness and spatial distribution of the comet measured over a 4 month period of time on either side of the comet's Perihelion on 2020 July 3. The water production rate in s−1 was moderately asymmetric around Perihelion and varied with the heliocentric distance, r, in au as (6.9 ± 0.5) × 1028 r −2.5±0.2 and (10.1 ± 0.5) × 1028 r −3.5±0.1 before and after Perihelion, respectively. This is consistent with the comet having been through the planetary region of the solar system on one or more previous apparitions. Water production rates as large as 5.27 × 1030 s−1 were determined shortly after Perihelion, once the comet was outside the solar avoidance area of SWAN, when the comet was 0.324 au from the Sun.
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Unusual Water Production Activity of Comet C/2012 S1 (ISON): Outbursts and Continuous Fragmentation
The Astrophysical journal letters, 2014Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, N. Fougere, Stéphane FerronAbstract:The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyα camera on the SOlar and Heliospheric Observer (SOHO) satellite observed the hydrogen coma of comet C/2012 S1 (ISON) for most of the last month of its activity from 2013 October 24 to November 24, ending just 4 days before Perihelion and its final disruption. The water production rate of the comet was determined from these observations. SOHO has been operating in a halo orbit around the Earth-Sun L1 Lagrange point since its launch in late 1995. Most water vapor produced by comets is ultimately photodissociated into two H atoms and one O atom producing a huge hydrogen coma that is routinely observed in the daily SWAN images in comets of sufficient brightness. Water production rates were calculated from 22 images over most of the last month of the pre-Perihelion apparition. The water production rate increased very slowly on average from October 24.9 until November 12.9, staying between 1.8 and 3.4 × 1028 s-1, after which it increased dramatically, reaching 1.6 to 2 × 1030 s-1 from November 21.6 to 23.6. It was not detected after Perihelion on December 3.7 when it should have been visible. We examine the active surface area necessary to explain the water production rate and its variation and are able to place constraints on the physical size of the original nucleus necessary to account for the large amount of activity from November 12.9 and until just before Perihelion.
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The water production rate of Rosetta target Comet 67P/ Churyumov-Gerasimenko near Perihelion in 1996, 2002 and 2009 from Lyman α observations with SWAN/SOHO
Planetary and Space Science, 2014Co-Authors: Jean-loup Bertaux, M.r. Combi, Eric Quémerais, Walter SchmidtAbstract:We report here the observations of the hydrogen cloud in Lyman alpha emission of comet 67P/ Churyumov-Gerasimenko at the last three passages through its Perihelion, in 1996, 2002 and 2009. This comet became the target of ESA space mission Rosetta in 2003, and is therefore of particular interest. The data were collected with the SWAN instrument on board SOHO, the main mission of which is to record all-sky images of interplanetary neutral hydrogen, in order to monitor the solar wind latitude distribution. For the 2009 Perihelion, a dedicated campaign was implemented and allowed to collect 26 smaller and more refined images around the position of the comet, from which a unique series of H2O production rates could be derived by comparison with a model, for the period from 2 to 50 days after Perihelion. To our knowledge, these are the only determination of H2O production rate for 2009. In addition, we could retrieve the H emission at the two previous perihelia in 1996 and 2002, thanks to serendipitous observations of comets as part of the all-sky monitoring program: 4 and 10 respectively for 1996 and 2002. While the Perihelion distance to sun decreased continuously (1.300, 1.292, 1.246 AU respectively for 1996, 2002, 2009), the average production Q(H2O) just after Perihelion did not increase accordingly: 1.30×1028, 1.70×1028, and 5.65×1027 mol s−1. Comparison with 1982 IUE measurement of 6×1027 mol s-1 suggests no rapid aging of the comet, and we may expect a similar level of activity at next Perihelion in August 2015. The production rate in 2009 showed a peak around 16.4 days post-Perihelion, with a suggestion of a second peak at ~40 days, and a somewhat reduced rate in between (though SWAN measurements are incomplete). These measurements may help the planning of Rosetta activities around the next Perihelion.
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Water Production in Comets C/2011 l4 (PanSTARRS) and C/2012 f6 (Lemmon) from observations with SOHO/SWAN
Astronomical Journal, 2014Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, Stéphane Ferron, G. AptekarAbstract:Comets C/2011 L4 (PanSTARRS) and C/2012 F6 (Lemmon) were observed throughout their 2012-2013 apparitions with the Solar Wind Anisotropies (SWAN) all-sky hydrogen Lyα camera on board the Solar and Heliosphere Observatory (SOHO) satellite. SOHO has been in a halo orbit around the L1 Earth-Sun Lagrange point since early 1996 and has been observing the interplanetary medium and comets beginning with C/1996 B2 (Hyakutake). The global water production from these comets was determined from an analysis of the SWAN Lyα camera observations. Comet C/2011 L4 (PanSTARRS), which reached its Perihelion distance of 0.302 AU on 2013 March 10.17, was observed on 50 days between 2013 January 29 and April 30. Comet C/2012 F6 (Lemmon), which reached its Perihelion distance of 0.731 AU on 2013 March 24.51, was observed on 109 days between 2012 November 29 and 2013 June 31. The maximum water production rates were ~1 × 1030 molecules s-1 for both comets. The activities of both comets were asymmetric about Perihelion. C/2011 L4 (PanSTARRS) was more active before Perihelion than after, but C/2012 F6 (Lemmon) was more active after Perihelion than before.
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Water production rate of Comet C/2009 P1 (Garradd) throughout the 2011-2012 apparition: Evidence for an icy grain halo
Icarus, 2013Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, Stéphane Ferron, N. FougereAbstract:The all-sky hydrogen Lyman-alpha camera, SWAN (Solar Wind Anisotropies), on the SOlar and Heliospheric Observatory (SOHO) satellite made observations of the hydrogen coma of comet C/2009 P1 (Garradd) throughout its apparition from August 15, 2011 through April 6, 2012. SOHO has been operating in a halo orbit around the Earth-Sun L1 Lagrange point since its launch in late 1995. Most water vapor produced by the comet is ultimately photodissociated into two H atoms and one O atom producing a huge atomic hydrogen coma that is routinely observed in the daily full-sky SWAN images in comets of sufficient brightness. Water production rates were calculated from 117 images over 8 months of the apparition yielding about 1 observation every 2 days on the average. The activity during much of the pre-Perihelion leg was much larger than the post-Perihelion leg and varied rather irregularly, not following the more typical steadily increasing trend with decreasing heliocentric distance. It varied generally between 1 and 3 x 1029 s-1, with a peak value of 4 x 1029 s-1 on November 3, 2011, 50 days before Perihelion. The elevated production rate from the very large SWAN field-of-view compared with smaller aperture observations could be consistent with water production from icy particles rather than from gas sublimated directly from the nucleus. Scenarios for the nature and production of the icy grain source are explored. During the post-Perihelion leg the water production rate decreased more uniformly and typically from 2 x 1029 s-1 at Perihelion, approximately as r-3.2, where r is the heliocentric distance. This is consistent with water sublimation from a reasonably constant total surface area
Stéphane Ferron - One of the best experts on this subject based on the ideXlab platform.
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Water Production Rate of C/2020 F3 (NEOWISE) from SOHO/SWAN over Its Active Apparition
The Astrophysical journal letters, 2021Co-Authors: Michael R Combi, Jean-loup Bertaux, Eric Quémerais, J. Teemu T. Mäkinen, Stéphane FerronAbstract:C/2020 F3 (NEOWISE) was discovered in images from the Near Earth Object program of the Wide-Field Infrared Survey Explorer (NEOWISE) taken on 2020 March 27 and has become the Great Comet of 2020. The Solar Wind ANisotropies (SWAN) camera on the Solar and Heliospheric Observatory (SOHO) spacecraft, located in a halo orbit around the Earth–Sun L1 Lagrange point, makes daily full-sky images of hydrogen Lyα. Water production rates were determined from the SWAN hydrogen Lyα brightness and spatial distribution of the comet measured over a 4 month period of time on either side of the comet's Perihelion on 2020 July 3. The water production rate in s−1 was moderately asymmetric around Perihelion and varied with the heliocentric distance, r, in au as (6.9 ± 0.5) × 1028 r −2.5±0.2 and (10.1 ± 0.5) × 1028 r −3.5±0.1 before and after Perihelion, respectively. This is consistent with the comet having been through the planetary region of the solar system on one or more previous apparitions. Water production rates as large as 5.27 × 1030 s−1 were determined shortly after Perihelion, once the comet was outside the solar avoidance area of SWAN, when the comet was 0.324 au from the Sun.
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Unusual Water Production Activity of Comet C/2012 S1 (ISON): Outbursts and Continuous Fragmentation
The Astrophysical journal letters, 2014Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, N. Fougere, Stéphane FerronAbstract:The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyα camera on the SOlar and Heliospheric Observer (SOHO) satellite observed the hydrogen coma of comet C/2012 S1 (ISON) for most of the last month of its activity from 2013 October 24 to November 24, ending just 4 days before Perihelion and its final disruption. The water production rate of the comet was determined from these observations. SOHO has been operating in a halo orbit around the Earth-Sun L1 Lagrange point since its launch in late 1995. Most water vapor produced by comets is ultimately photodissociated into two H atoms and one O atom producing a huge hydrogen coma that is routinely observed in the daily SWAN images in comets of sufficient brightness. Water production rates were calculated from 22 images over most of the last month of the pre-Perihelion apparition. The water production rate increased very slowly on average from October 24.9 until November 12.9, staying between 1.8 and 3.4 × 1028 s-1, after which it increased dramatically, reaching 1.6 to 2 × 1030 s-1 from November 21.6 to 23.6. It was not detected after Perihelion on December 3.7 when it should have been visible. We examine the active surface area necessary to explain the water production rate and its variation and are able to place constraints on the physical size of the original nucleus necessary to account for the large amount of activity from November 12.9 and until just before Perihelion.
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Water Production in Comets C/2011 l4 (PanSTARRS) and C/2012 f6 (Lemmon) from observations with SOHO/SWAN
Astronomical Journal, 2014Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, Stéphane Ferron, G. AptekarAbstract:Comets C/2011 L4 (PanSTARRS) and C/2012 F6 (Lemmon) were observed throughout their 2012-2013 apparitions with the Solar Wind Anisotropies (SWAN) all-sky hydrogen Lyα camera on board the Solar and Heliosphere Observatory (SOHO) satellite. SOHO has been in a halo orbit around the L1 Earth-Sun Lagrange point since early 1996 and has been observing the interplanetary medium and comets beginning with C/1996 B2 (Hyakutake). The global water production from these comets was determined from an analysis of the SWAN Lyα camera observations. Comet C/2011 L4 (PanSTARRS), which reached its Perihelion distance of 0.302 AU on 2013 March 10.17, was observed on 50 days between 2013 January 29 and April 30. Comet C/2012 F6 (Lemmon), which reached its Perihelion distance of 0.731 AU on 2013 March 24.51, was observed on 109 days between 2012 November 29 and 2013 June 31. The maximum water production rates were ~1 × 1030 molecules s-1 for both comets. The activities of both comets were asymmetric about Perihelion. C/2011 L4 (PanSTARRS) was more active before Perihelion than after, but C/2012 F6 (Lemmon) was more active after Perihelion than before.
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Water production rate of Comet C/2009 P1 (Garradd) throughout the 2011-2012 apparition: Evidence for an icy grain halo
Icarus, 2013Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, Stéphane Ferron, N. FougereAbstract:The all-sky hydrogen Lyman-alpha camera, SWAN (Solar Wind Anisotropies), on the SOlar and Heliospheric Observatory (SOHO) satellite made observations of the hydrogen coma of comet C/2009 P1 (Garradd) throughout its apparition from August 15, 2011 through April 6, 2012. SOHO has been operating in a halo orbit around the Earth-Sun L1 Lagrange point since its launch in late 1995. Most water vapor produced by the comet is ultimately photodissociated into two H atoms and one O atom producing a huge atomic hydrogen coma that is routinely observed in the daily full-sky SWAN images in comets of sufficient brightness. Water production rates were calculated from 117 images over 8 months of the apparition yielding about 1 observation every 2 days on the average. The activity during much of the pre-Perihelion leg was much larger than the post-Perihelion leg and varied rather irregularly, not following the more typical steadily increasing trend with decreasing heliocentric distance. It varied generally between 1 and 3 x 1029 s-1, with a peak value of 4 x 1029 s-1 on November 3, 2011, 50 days before Perihelion. The elevated production rate from the very large SWAN field-of-view compared with smaller aperture observations could be consistent with water production from icy particles rather than from gas sublimated directly from the nucleus. Scenarios for the nature and production of the icy grain source are explored. During the post-Perihelion leg the water production rate decreased more uniformly and typically from 2 x 1029 s-1 at Perihelion, approximately as r-3.2, where r is the heliocentric distance. This is consistent with water sublimation from a reasonably constant total surface area
M.r. Combi - One of the best experts on this subject based on the ideXlab platform.
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Unusual Water Production Activity of Comet C/2012 S1 (ISON): Outbursts and Continuous Fragmentation
The Astrophysical journal letters, 2014Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, N. Fougere, Stéphane FerronAbstract:The Solar Wind ANisotropies (SWAN) all-sky hydrogen Lyα camera on the SOlar and Heliospheric Observer (SOHO) satellite observed the hydrogen coma of comet C/2012 S1 (ISON) for most of the last month of its activity from 2013 October 24 to November 24, ending just 4 days before Perihelion and its final disruption. The water production rate of the comet was determined from these observations. SOHO has been operating in a halo orbit around the Earth-Sun L1 Lagrange point since its launch in late 1995. Most water vapor produced by comets is ultimately photodissociated into two H atoms and one O atom producing a huge hydrogen coma that is routinely observed in the daily SWAN images in comets of sufficient brightness. Water production rates were calculated from 22 images over most of the last month of the pre-Perihelion apparition. The water production rate increased very slowly on average from October 24.9 until November 12.9, staying between 1.8 and 3.4 × 1028 s-1, after which it increased dramatically, reaching 1.6 to 2 × 1030 s-1 from November 21.6 to 23.6. It was not detected after Perihelion on December 3.7 when it should have been visible. We examine the active surface area necessary to explain the water production rate and its variation and are able to place constraints on the physical size of the original nucleus necessary to account for the large amount of activity from November 12.9 and until just before Perihelion.
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Water Production in Comets C/2011 l4 (PanSTARRS) and C/2012 f6 (Lemmon) from observations with SOHO/SWAN
Astronomical Journal, 2014Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, Stéphane Ferron, G. AptekarAbstract:Comets C/2011 L4 (PanSTARRS) and C/2012 F6 (Lemmon) were observed throughout their 2012-2013 apparitions with the Solar Wind Anisotropies (SWAN) all-sky hydrogen Lyα camera on board the Solar and Heliosphere Observatory (SOHO) satellite. SOHO has been in a halo orbit around the L1 Earth-Sun Lagrange point since early 1996 and has been observing the interplanetary medium and comets beginning with C/1996 B2 (Hyakutake). The global water production from these comets was determined from an analysis of the SWAN Lyα camera observations. Comet C/2011 L4 (PanSTARRS), which reached its Perihelion distance of 0.302 AU on 2013 March 10.17, was observed on 50 days between 2013 January 29 and April 30. Comet C/2012 F6 (Lemmon), which reached its Perihelion distance of 0.731 AU on 2013 March 24.51, was observed on 109 days between 2012 November 29 and 2013 June 31. The maximum water production rates were ~1 × 1030 molecules s-1 for both comets. The activities of both comets were asymmetric about Perihelion. C/2011 L4 (PanSTARRS) was more active before Perihelion than after, but C/2012 F6 (Lemmon) was more active after Perihelion than before.
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The water production rate of Rosetta target Comet 67P/ Churyumov-Gerasimenko near Perihelion in 1996, 2002 and 2009 from Lyman α observations with SWAN/SOHO
Planetary and Space Science, 2014Co-Authors: Jean-loup Bertaux, M.r. Combi, Eric Quémerais, Walter SchmidtAbstract:We report here the observations of the hydrogen cloud in Lyman alpha emission of comet 67P/ Churyumov-Gerasimenko at the last three passages through its Perihelion, in 1996, 2002 and 2009. This comet became the target of ESA space mission Rosetta in 2003, and is therefore of particular interest. The data were collected with the SWAN instrument on board SOHO, the main mission of which is to record all-sky images of interplanetary neutral hydrogen, in order to monitor the solar wind latitude distribution. For the 2009 Perihelion, a dedicated campaign was implemented and allowed to collect 26 smaller and more refined images around the position of the comet, from which a unique series of H2O production rates could be derived by comparison with a model, for the period from 2 to 50 days after Perihelion. To our knowledge, these are the only determination of H2O production rate for 2009. In addition, we could retrieve the H emission at the two previous perihelia in 1996 and 2002, thanks to serendipitous observations of comets as part of the all-sky monitoring program: 4 and 10 respectively for 1996 and 2002. While the Perihelion distance to sun decreased continuously (1.300, 1.292, 1.246 AU respectively for 1996, 2002, 2009), the average production Q(H2O) just after Perihelion did not increase accordingly: 1.30×1028, 1.70×1028, and 5.65×1027 mol s−1. Comparison with 1982 IUE measurement of 6×1027 mol s-1 suggests no rapid aging of the comet, and we may expect a similar level of activity at next Perihelion in August 2015. The production rate in 2009 showed a peak around 16.4 days post-Perihelion, with a suggestion of a second peak at ~40 days, and a somewhat reduced rate in between (though SWAN measurements are incomplete). These measurements may help the planning of Rosetta activities around the next Perihelion.
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Water production rate of Comet C/2009 P1 (Garradd) throughout the 2011-2012 apparition: Evidence for an icy grain halo
Icarus, 2013Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Eric Quémerais, Stéphane Ferron, N. FougereAbstract:The all-sky hydrogen Lyman-alpha camera, SWAN (Solar Wind Anisotropies), on the SOlar and Heliospheric Observatory (SOHO) satellite made observations of the hydrogen coma of comet C/2009 P1 (Garradd) throughout its apparition from August 15, 2011 through April 6, 2012. SOHO has been operating in a halo orbit around the Earth-Sun L1 Lagrange point since its launch in late 1995. Most water vapor produced by the comet is ultimately photodissociated into two H atoms and one O atom producing a huge atomic hydrogen coma that is routinely observed in the daily full-sky SWAN images in comets of sufficient brightness. Water production rates were calculated from 117 images over 8 months of the apparition yielding about 1 observation every 2 days on the average. The activity during much of the pre-Perihelion leg was much larger than the post-Perihelion leg and varied rather irregularly, not following the more typical steadily increasing trend with decreasing heliocentric distance. It varied generally between 1 and 3 x 1029 s-1, with a peak value of 4 x 1029 s-1 on November 3, 2011, 50 days before Perihelion. The elevated production rate from the very large SWAN field-of-view compared with smaller aperture observations could be consistent with water production from icy particles rather than from gas sublimated directly from the nucleus. Scenarios for the nature and production of the icy grain source are explored. During the post-Perihelion leg the water production rate decreased more uniformly and typically from 2 x 1029 s-1 at Perihelion, approximately as r-3.2, where r is the heliocentric distance. This is consistent with water sublimation from a reasonably constant total surface area
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Water Production in Comets 2001 Q4 (NEAT) and 2002 T7 (LINEAR) Determined from SOHO/SWAN Observations
Astronomical Journal, 2009Co-Authors: M.r. Combi, J.t.t. Mäkinen, Jean-loup Bertaux, Y. Lee, Eric QuémeraisAbstract:The SWAN all-sky camera on the Solar and Heliospheric Observatory (SOHO) spacecraft detected the hydrogen Lyman-alpha (Lyα) comae of comets 2001 Q4 NEAT and 2002 T7 LINEAR for large portions of their Perihelion apparitions in 2003 and 2004. C/2001 Q4 NEAT was observed from 2003 September 14 through 2004 November 2, covering heliocentric distances from 3.23 AU before Perihelion to 2.75 AU after, and C/2002 T7 LINEAR was observed from 2003 December 4 through 2004 August 6, covering heliocentric distances from 2.52 AU before Perihelion to 2.09 AU after. We combined the full set of comet specific and full-sky observations and used our time-resolved model (TRM), which enables us to extract continuous values of the daily-average value of the water production rate throughout most of this entire period. The average power-law fit to the production rate variation of C/2001 Q4 NEAT with heliocentric distance, r, gives 3.5 × 1029 r –1.7 and that for C/2002 T7 LINEAR gives 4.6 × 1029 r –2.0. Both comets show roughly a factor of 2 asymmetry in activity about Perihelion, being more active before Perihelion. C/2001 Q4 NEAT showed a production rate outburst about 30 days before Perihelion (2004 April 15) and then a large extended increase above the nominal trend from 50 to 70 days after Perihelion (2004 July 5-July 25).
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Recurrent Cometary Activity in Near-Earth Object (3552) Don Quixote
The Planetary Science Journal, 2020Co-Authors: Michael Mommert, Matthew M Knight, Nicolas Biver, Joseph L. Hora, David E. Trilling, Kacper Wierzchos, David Polishook, Nick Moskovitz, Michael S. P. Kelley, Howard A. SmithAbstract:We report on observations of activity in near-Earth object (3552) Don Quixote using the Spitzer Space Telescope and ground-based telescopes around its 2018 Perihelion passage. Spitzer observations obtained six months before Perihelion show extended emission around the target's nucleus that is most likely caused by molecular band emission from either CO2 or CO, but we find no significant emission from dust. Ground-based optical observations taken close to Perihelion reveal for the first time activity in the optical wavelengths, which we attribute to solar light reflected from dust particles. IRAM millimeter radio observations taken around the same time are unable to rule out CO as the driver of the molecular band emission observed with Spitzer. The comparison of the gas activity presented here with observations performed during Don Quixote's previous apparition suggests that activity in Don Quixote is recurrent. We conclude that (3552) Don Quixote is most likely a weakly active comet.
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Hubble Space Telescope Imaging Polarimetry of Comet 67P/Churyumov-Gerasimenko Obtained During the Rosetta Mission
2015Co-Authors: Dean C. Hines, Edith Hadamcik, Anny Chantal Levasseur-regourd, Matthew M Knight, Vadym Kaydash, Ludmilla Kolokolova, Carey M. Lisse, Karri Muinonen, Max Mutchler, Yuriy ShkuratovAbstract:We present pre- and post-Perihelion, high-spatial resolution (0.05 arcsec/pixel) 0.6 micron imaging polarimetry of Comet 67P/Churyumov-Gerasimenko taken with the Advanced Camera for Surveys aboard the Hubble Space Telescope (HST). The pre-Perihelion observations were obtained at two epochs chosen to bracket the times when the closest orbits of Rosetta were flown (down to 10 km for extended periods: 2014-Aug-19: rh = 3.52 au, Δ = 2.76 au, α ≈ 12.0˚) and the Philae landing took place (2014-Nov-17: rh = 2.96 au, Δ = 3.43 au, α ≈ 15.7˚). Our preliminary analyses of both pre-Perihelion epochs shows that the polarization position angle lies in the scattering plane, thus is negative, with a degree of polarization p% ≈ -2%. The two post-Perihelion epochs were matched to the first time after Perihelion that the comet was observable with HST (2015-Oct-10: rh = 1.43 au, Δ = 1.80 au, α ≈ 33.5˚), and when the comet was again viewed at small phase angle (2016-Feb-19: rh = 2.40 au, Δ = 1.49 au, α ≈ 12.0˚). We discuss our polarimetry results in context with in situ measurements of dust particles obtained with the Rosetta spacecraft.
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preliminary analysis of soho stereo observations of sungrazing comet ison c 2012 s1 around Perihelion
The Astrophysical Journal, 2014Co-Authors: Matthew M Knight, Karl BattamsAbstract:We present photometric and morphological analysis of the behavior of sungrazing comet C/2012 S1 ISON in Solar and Heliospheric Observatory (SOHO) and Solar TErrestrial RElations Observatory (STEREO) images around its Perihelion on 2013 November 28.779 UT. ISON brightened gradually November 20-26 with a superimposed outburst on November 21.3-23.5. The slope of brightening changed about November 26.7 and was significantly steeper in SOHO's orange and clear filter images until November 27.9 when it began to flatten out, reaching a peak about November 28.1 (r H ≈ 17 R ☉), then fading before brightening again from November 28.6 (r H ≈ 5 R ☉) until disappearing behind the occulting disk. ISON brightened continuously as it approached Perihelion while visible in all other telescopes/filters. The central condensation disappeared about November 28.5 and the leading edge became progressively more elongated until Perihelion. These photometric and morphological behaviors are reminiscent of the tens of meter-sized Kreutz comets regularly observed by SOHO and STEREO and strongly suggest that the nucleus of ISON was destroyed prior to Perihelion. This is much too small to support published gas production rates and implies significant mass loss and/or disruption in the days and weeks leading up to Perihelion. No central condensation was seen post-Perihelion. The post-Perihelion lightcurve was nearly identical in all telescopes/filters and fell slightly steeper than . This implies that the brightness was dominated by reflected solar continuum off of remnant dust in the coma/tail and that any remaining active nucleus was <10 m in radius.
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preliminary analysis of soho stereo observations of sungrazing comet ison c 2012 s1 around Perihelion
arXiv: Earth and Planetary Astrophysics, 2014Co-Authors: Matthew M Knight, Karl BattamsAbstract:We present photometric and morphological analysis of the behavior of sungrazing comet C/2012 S1 ISON in SOHO and STEREO images around its Perihelion on 2013 November 28.779 UT. ISON brightened gradually November 20-26 with a superimposed outburst on November 21.3-23.5. The slope of brightening changed about November 26.7 and was significantly steeper in SOHO's orange and clear filter images until November 27.9 when it began to flatten out, reaching a peak about November 28.1 ($r_H{\sim}17 R_\odot$), then fading before brightening again from November 28.6 ($r_H{\sim}5 R_\odot$) until disappearing behind the occulting disc. ISON brightened continuously as it approached Perihelion while visible in all other telescopes/filters. The central condensation disappeared about November 28.5 and the leading edge became progressively more elongated until Perihelion. These photometric and morphological behaviors are reminiscent of the tens of meter sized Kreutz comets regularly observed by SOHO and STEREO and strongly suggest that the nucleus of ISON was destroyed prior to Perihelion. This is much too small to support published gas production rates and implies significant mass loss and/or disruption in the days and weeks leading up to Perihelion. No central condensation was seen post-Perihelion. The post-Perihelion lightcurve was nearly identical in all telescopes/filters and fell slightly steeper than $r_H^{-2}$. This implies that the brightness was dominated by reflected solar continuum off of remnant dust in the coma/tail and that any remaining active nucleus was <10 m in radius.