17 research outputs found
Solar wind velocities for C/2013 R1 (Lovejoy)
No full textThis dataset was analysed and presented in the ‘Solar Wind Velocities at Comets C/2011 L4 Pan-STARRS and C/2013 R1 Lovejoy derived using a New Image Analysis Technique’ paper. Submitted to JGR - Space Physics.Please contact the author at [email protected] for info on the software. This dataset was collected from amateur astrophotographers from around the world and observations from the Isaac Newton Telescope were undertaken by Y. Ramanjooloo and K. Birkett. The data spanned two weeks on either side of the comet’s perihelion and covers part of Carrington Rotation 2144 and 2145.Each image was processed through IDL using the main technique described in the paper to produce radial solar wind velocity estimates from the cometary ion tail of comet C/2013 R1 (Lovejoy).The processed variables, including the final solar wind velocity results are stored as individual .sav files for each image. IDL is required to open and analyse these .sav files. the python package readsav is also available - see links below.In repository:1. Image of comet C/2013 R1 (Lovejoy) acquired by G. Rhemann on 13 December 2013 at 03:41 UT[https://figshare.com/ndownloader/files/31785983/preview/31785983/preview.jpg]2. Data coverage of C/2013 R1 (Lovejoy) as observed from Earth and mapped onto the comet’s orbital plane. The Sun is at (0,0) and the perihelion defines the y-axis. [https://figshare.com/ndownloader/files/31785986/preview/31785986/preview.jpg]3. Processed images from amateur astronomers as .sav files. To produce a plot of the solar wind velocities, the user will need to access these results from each .sav file and concatenate them.File naming convention is comet denomination + datetime_UTC + observer + .fits4. Processed INT images as .fits files. The raw data was processed through THELI for CCD distortion correction and solved through Astrometry.net. Each INT Wide-Field Camera image contains 4 CCDs (labeled 10,20,30, 40) [https://www.ing.iac.es/astronomy/instruments/wfc/]File naming convention for INT images is comet denomination + datetime_UTC + image number + CCD + filter + exptime + .fitsImages used for the non-radial velocity vector flowmaps are labeled with '_flowmap'. The raw data (also through the Isaac Newton Group of Telescopes), coadded and difference images are available upon request. ***Note:***.sav files are saved variables processed via IDL. More info can be found here:.sav: https://www.l3harrisgeospatial.com/docs/save.htmlIDL : https://www.l3harrisgeospatial.com/The following python package is available to process .sav files though the authors have no experience with this package.https://docs.scipy.org/doc/scipy/reference/generated/scipy.io.readsav.html<br
Comets as natural laboratories: Interpretations of the structure of the inner heliosphere
No full textComets can be considered to be natural laboratories of the inner heliosphere, as their ion tails trace the solar wind flow. Much has been learnt about the heliosphere’s structure from in situ solar wind spacecraft observations. Their coverage is however limited in time and space. This thesis proposes to address these constraints and ascertain the validity of analysing comets’ ion tails as complementary sources of information on dynamical heliospheric phenomena and the underlying continuous solar wind. Solar wind conditions influence comets’ induced magnetotails, formed through the draping of the heliospheric magnetic field by the velocity shear in the mass-loaded solar wind. I present a novel imaging technique and software to exploit the vast catalogues of amateur and professional images of comet ion tails. My projection technique uses the comet’s orbital plane to sample its ion tail as a proxy for determining radial solar wind velocities in each comet’s vicinity. Making full use of many observing stations from astrophotography hobbyists to professional observatories and spacecraft, this approach is applied to several comets observed in recent years. Complementary velocities, derived from folding ion rays and a velocity profile map built from consecutive images, are provided as an alternative means of quantifying the solar wind-cometary ionosphere interaction. I review the validity of these techniques by comparing near-Earth comets to solar wind models in the inner heliosphere and extrapolated measurements by ACE to a near-Earth comet’s orbit. My radial velocities are mapped back to the solar wind source surface to identify sources of the quiescent solar wind and heliospheric current sheet crossings. Comets are found to be good indicators of solar wind structure, but the quality of results is strongly dependent on the observing geometry. Many ion tails also show a constant curvature, so far unexplained, which further complicates the interpretation of tails’ orientations
Radial and Non-Radial Solar wind velocities for C/2011 L4 (PANSTARRS)
No full textThis dataset was analysed and presented in the ‘Solar Wind Velocities at Comets C/2011 L4 Pan-STARRS and C/2013 R1 Lovejoy derived using a New Image Analysis Technique’ paper. Submitted to JGR - Space Physics.Please contact the author at [email protected] for info on the software. Only STEREO B data was successfully analysed for comet C/2011 L4 (PANSTARRS). STEREO A and Earth-based images are available but are not usable with this technique due to the low orbit plane angle. The difference images used in this study were made available for analysis by K. Battams (NRL).Each difference image was processed through IDL using the main technique described in the paper to produce radial solar wind velocity estimates from the cometary ion tail of comet C/2011 L4 (PANSTARRS). The processed variables, including the final solar wind velocity results are stored as individual .sav files for each image.To produce a plot, the solar wind velocities must be obtained from each image OR use the concatenated solar wind velocities saved as c2011l4_SWspeed_20140619.sav or the c2011l4_bundlepos_20140626.sav, which was created from a selection of images described in the paper to produce non-radial solar wind velocities for the Flow Vector Maps section described in the paper
Solar wind velocities for comet C/2013 R1 (Lovejoy) during low orbit plane angles
No full textThis dataset was analysed and presented in the ‘Solar Wind Velocities at Comets C/2011 L4 Pan-STARRS and C/2013 R1 Lovejoy derived using a New Image Analysis Technique’ paper. Submitted to JGR - Space Physics.Please contact the author at [email protected] for info on the software. This dataset was collected from amateur astrophotographers from around the world. The data spanned two weeks on either side of the comet’s perihelion and covers part of Carrington Rotation 2144 and 2145.Each image was processed through IDL using the main technique described in the paper to produce radial solar wind velocity estimates from the cometary ion tail of comet C/2013 R1 (Lovejoy).The processed variables, including the final solar wind velocity results are stored as individual .sav files for each image. IDL is required to open and analyse these .sav files. the python package readsav is also available - see links below.In repository:1. Processed images as .sav files. To produce a plot of the solar wind velocities, the user will need to access these results from each .sav file and concatenate them.File naming convention is comet denomination + datetime_UTC + observer + .fits***Note:***.sav files are saved variables processed via IDL. More info can be found here:.sav: https://www.l3harrisgeospatial.com/docs/save.htmlIDL : https://www.l3harrisgeospatial.com/The following python package is available to process .sav files though the authors have no experience with this package.https://docs.scipy.org/doc/scipy/reference/generated/scipy.io.readsav.htm
The 67P/Churyumov- Gerasimenko observation campaign in support of the Rosetta mission
No full textSnodgrass, Colin et al.-- Full list of authors: Snodgrass, C.; A'Hearn, M. F.; Aceituno, F.; Afanasiev, V.; Bagnulo, S.; Bauer, J.; Bergond, G.; Besse, S.; Biver, N.; Bodewits, D.; Boehnhardt, H.; Bonev, B. P.; Borisov, G.; Carry, B.; Casanova, V.; Cochran, A.; Conn, B. C.; Davidsson, B.; Davies, J. K.; de León, J.; de Mooij, E.; de Val-Borro, M.; Delacruz, M.; DiSanti, M. A.; Drew, J. E.; Duffard, R.; Edberg, N. J. T.; Faggi, S.; Feaga, L.; Fitzsimmons, A.; Fujiwara, H.; Gibb, E. L.; Gillon, M.; Green, S. F.; Guijarro, A.; Guilbert-Lepoutre, A.; Gutiérrez, P. J.; Hadamcik, E.; Hainaut, O.; Haque, S.; Hedrosa, R.; Hines, D.; Hopp, U.; Hoyo, F.; Hutsemékers, D.; Hyland, M.; Ivanova, O.; Jehin, E.; Jones, G. H.; Keane, J. V.; Kelley, M. S. P.; Kiselev, N.; Kleyna, J.; Kluge, M.; Knight, M. M.; Kokotanekova, R.; Koschny, D.; Kramer, E. A.; López-Moreno, J. J.; Lacerda, P.; Lara, L. M.; Lasue, J.; Lehto, H. J.; Levasseur-Regourd, A. C.; Licandro, J.; Lin, Z. Y.; Lister, T.; Lowry, S. C.; Mainzer, A.; Manfroid, J.; Marchant, J.; McKay, A. J.; McNeill, A.; Meech, K. J.; Micheli, M.; Mohammed, I.; Monguió, M.; Moreno, F.; Muñoz, O.; Mumma, M. J.; Nikolov, P.; Opitom, C.; Ortiz, J. L.; Paganini, L.; Pajuelo, M.; Pozuelos, F. J.; Protopapa, S.; Pursimo, T.; Rajkumar, B.; Ramanjooloo, Y.; Ramos, E.; Ries, C.; Riffeser, A.; Rosenbush, V.; Rousselot, P.; Ryan, E. L.; Santos-Sanz, P.; Schleicher, D. G.; Schmidt, M.; Schulz, R.; Sen, A. K.; Somero, A.; Sota, A.; Stinson, A.; Sunshine, J. M.; Thompson, A.; Tozzi, G. P.; Tubiana, C.; Villanueva, G. L.; Wang, X.; Wooden, D. H.; Yagi, M.; Yang, B.; Zaprudin, B.; Zegmott, T. J.We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively 'well-behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends-in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies. This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Author(s)C.S. is supported by a UK Science & Technology Facilities Council (STFC) Rutherford fellowship. A.F. acknowledges support from STFC grant ST/L000709/1. S.F.G. acknowledges support from the STFC (grant ST/L000776/1). J.K. is supported by NSF grant 1413736. H.J.L., B.Z. and A.S. acknowledge the support of the Academy of Finland (grant no. 277375). J.L. and J.d.L. acknowledge support from the AYA2015-67772-R (MINECO, Spain). J.L. and A.C.L.-R. acknowledge support from CNES, the French Space Agency, for this work in relation with CONSERT and MIDAS on board Rosetta. Z.Y.L. and X.W. were supported by NSC 102-2112-M-008-003-MY3 of the Ministry of Science and Technology, Taiwan, and the National Natural Sciences Foundations of China (contract nos. 11073051 and 11473066). C.O. acknowledges the support of the FNRS.
We acknowledge the contribution of the Europlanet EU FP7/H2020 framework in supporting meetings that initiated this campaign in 2012 and brought many of us together to discuss the results in 2016. We thank the Royal Society and the organizers of the ‘Cometary science after Rosetta’ meeting for the invitation to present the results of the campaign. Finally, we thank the many observatories involved in these observations for their support in allocating significant time to observing 67P, especially ESO, Gemini and Observatorios de Canarias del IAC (through the CCI International Time Programme) for enabling the long-term baseline of observations. We are grateful for the efforts of various support astronomers in assisting with the observations: in particular, Ian Skillen at the ING; Fumiaki Nakata, Finet Francois and the HSC Queue Working Group at Subaru; Thomas Granzer at STELLA; David Abreu and Pablo Ruiz from Ataman Science, Spain, for supporting the OGS observations
The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets
No full textThis review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics
280 one-opposition near-earth asteroids recovered by the EURONEAR with the Isaac Newton telescope
No full textContext. One-opposition near-Earth asteroids (NEAs) are growing in number, and they must be recovered to prevent loss and mismatch risk, and to improve their orbits, as they are likely to be too faint for detection in shallow surveys at future apparitions. Aims. We aimed to recover more than half of the one-opposition NEAs recommended for observations by the Minor Planet Center (MPC) using the Isaac Newton Telescope (INT) in soft-override mode and some fractions of available D-nights. During about 130 h in total between 2013 and 2016, we targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs), observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76% of all targets). Methods. Engaging a core team of about ten students and amateurs, we used the THELI, Astrometrica, and the FindOrb software to identify all moving objects using the blink and track-And-stack method for the faintest targets and plotting the positional uncertainty ellipse from NEODyS. Results. Most targets and recovered objects had apparent magnitudes centered around V ~ 22.8 mag, with some becoming as faint as V ~ 24 mag. One hundred and three objects (representing 28% of all targets) were recovered by EURONEAR alone by Aug. 2017. Orbital arcs were prolonged typically from a few weeks to a few years; our oldest recoveries reach 16 years. The O-C residuals for our 1854 NEA astrometric positions show that most measurements cluster closely around the origin. In addition to the recovered NEAs, 22 000 positions of about 3500 known minor planets and another 10 000 observations of about 1500 unknown objects (mostly main-belt objects) were promptly reported to the MPC by our team. Four new NEAs were discovered serendipitously in the analyzed fields and were promptly secured with the INT and other telescopes, while two more NEAs were lost due to extremely fast motion and lack of rapid follow-up time. They increase the counting to nine NEAs discovered by the EURONEAR in 2014 and 2015. Conclusions. Targeted projects to recover one-opposition NEAs are efficient in override access, especially using at least two-meter class and preferably larger field telescopes located in good sites, which appear even more efficient than the existing surveys
