Publications of Jean Manfroid
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See detailTRAPPIST monitoring of comet C/2013 A1 (Siding Spring)
Opitom, Cyrielle ULiege; Jehin, Emmanuel ULiege; Manfroid, Jean ULiege et al

in Bulletin of the American Astronomical Society (2014, November 01), 46

C/2013 A1 (Siding Spring) is a long period comet discovered by Robert H McNaught at Siding Spring Observatory in Australia on January 3, 2013 at 7.2 au from the Sun. This comet will make a close encounter ... [more ▼]

C/2013 A1 (Siding Spring) is a long period comet discovered by Robert H McNaught at Siding Spring Observatory in Australia on January 3, 2013 at 7.2 au from the Sun. This comet will make a close encounter with Mars on October 19, 2014. At this occasion the comet will be extensively observed both from Earth and from several orbiters around Mars.On September 20, 2013 when the comet was around 5 au from the Sun, we started a monitoring with the TRAPPIST robotic telescope installed at La Silla observatory [1]. A set of narrowband cometary filters designed by the NASA for the Hale-Bopp Observing Campaign [2] is permanently mounted on the telescope along with classic Johnson-Cousins B, V, Rc, and Ic filters.We observed the comet continuously at least once a week from September 20, 2013 to April 6, 2014 with broad band filters. We then recovered the comet on May 20. At this time we could detect the gas and started the observations with narrow band filters until early November, covering the close approach to Mars and the perihelion passage.We present here our first results about comet Siding Springs. From the images in the broad band filters and in the dust continuum filters we derived A(θ)fρ values [3] and studied the evolution of the comet activity with the heliocentric distance from September 20, 2013 to early November 2014. We could also detect gas since May 20, 2014. We thus derived gas production rates using a Haser model [4]. We present the evolution of gas production rates and gas production rates ratios with the heliocentric distance.Finally, we discuss the dust and gas coma morphology. [less ▲]

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See detailThe TRAPPIST comet survey in 2014
Jehin, Emmanuel ULiege; Opitom, Cyrielle ULiege; Manfroid, Jean ULiege et al

in Bulletin of the American Astronomical Society (2014, November 01), 46

TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is ... [more ▼]

TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is devoted to the detection and characterisation of exoplanets and to the study of comets and other small bodies in the Solar System. A set of narrowband cometary filters designed by the NASA for the Hale-Bopp Observing Campaign [2] is permanently mounted on the telescope along with classic Johnson-Cousins filters. We describe here the hardware and the goals of the project. For relatively bright comets (V < 12) we measure several times a week the gaseous production rates (using a Haser model) and the spatial distribution of several species among which OH, NH, CN, C2 and C3 as well as ions like CO+. The dust production rates (Afrho) and color of the dust aredetermined through four dust continuum bands from the UV to the red (UC, BC, GC, RC filters). We will present the dust and gas production rates of the brightest comets observed in 2014: C/2012 K1 (PANSTARRS), C/2014 E2 (Jacques), C/2013 A1 (Siding Springs) and C/2013 V5 (Oukaimeden). Each of these comets have been observed at least once a week for several weeks to several months. Light curves with respect to the heliocentric distance will be presented and discussed. [1] Jehin et al., The Messenger, 145, 2-6, 2011.[2] Farnham et al., Icarus, 147, 180-204, 2000. [less ▲]

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See detailL'astronomie dans le monde - 11/2014
Manfroid, Jean ULiege

Article for general public (2014)

DDO 68 - La distancedes Pléiades - La rotation de M87 - Galaxies disques - M60- UCD1 - Galaxies géantes - Source gamma - BICEP2- L’origine d’Uranus et Neptune- HAT-P-11b - Rosetta - Une nouvelle molécule ... [more ▼]

DDO 68 - La distancedes Pléiades - La rotation de M87 - Galaxies disques - M60- UCD1 - Galaxies géantes - Source gamma - BICEP2- L’origine d’Uranus et Neptune- HAT-P-11b - Rosetta - Une nouvelle molécule interstellaire - L’eau du Système solaire - Cailloux interstellaires [less ▲]

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See detailL'astronomie dans le monde - 10/2014
Manfroid, Jean ULiege

Article for general public (2014)

HK Tauri - Histoires de supernovæ - Fusion intergalactique - Lithium - Des nouvelles de Gaia - Rosetta - Laniakeia

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See detailPhase resolved X-ray spectroscopy of HDE 228766: Probing the wind of an extreme Of+/WNLha star (Corrigendum)
Rauw, Grégor ULiege; Mahy, Laurent; Nazé, Yaël ULiege et al

in Astronomy and Astrophysics (2014), 569

Based on observations collected with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA), and on data collected at the San Pedro ... [more ▼]

Based on observations collected with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA), and on data collected at the San Pedro Mártir observatory (Mexico). Corrigendum [less ▲]

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See detailL'astronomie dans le monde - 09/2014
Manfroid, Jean ULiege

Article for general public (2014)

Rosetta la sonde cométaire arrive à destination - Exoplanètes remarquables - Mars - Vesta remet en question l’origine de la Terre - Météorite ferreuse sur Mars - Encelade - comète 2012 K1 (PanSTARRS ... [more ▼]

Rosetta la sonde cométaire arrive à destination - Exoplanètes remarquables - Mars - Vesta remet en question l’origine de la Terre - Météorite ferreuse sur Mars - Encelade - comète 2012 K1 (PanSTARRS) - SN2010jl - NGC 4651 - GRB ultra-long - Voie lactée et Andromède - E-ELT [less ▲]

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See detailThe TRAPPIST comet survey
Jehin, Emmanuel ULiege; Opitom, Cyrielle ULiege; Manfroid, Jean ULiege et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors - Book of Abstracts (2014, July 01)

TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is ... [more ▼]

TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is devoted to the detection and characterisation of exoplanets and to the study of comets and other small bodies in the Solar System. We describe here the hardware and the goals of the project and give an overview of the comet production rates monitoring after three years of operations. The telescope and observatory --- TRAPPIST's optical tube unit is a Ritchey-Chretien 0.6 meter telescope with a focal length of 4.8 meter. It is associated with a German equatorial mount that is, thanks to its direct drive system, extremely fast (up to 50 deg/s), accurate (tracking accuracy without autoguider better than 2'' in 10 min), and free of periodic error. The instrument is a Peltier cooled commercial camera equipped with a Fairchild 3041 back-illuminated 2k×2k chip. The pixel scale is 0.64''/pixel. Three read-out modes are available, the shortest read-out time being 2s. The total field of view of the camera is 22'×22'. It is associated to a custom-made dual filter wheel. One of the filter wheel contains broad band filters (Johnson B, V, R, Cousins Ic, Sloan z, and a special I+z filter), while the other contains the narrow-band NASA HB cometary filters (OH, NH, CN, CO+, C3, and C2 gaseous species; UC, BC, GC and RC solar continuum windows and a NaI D filter) [2]. The telescope is protected by a 5 meter diameter dome that was totally refurbished and automatized. The observatory is fully robotic and equipped with a weather station, an UPS and webcams. The la Silla site is excellent with more than 300 clear nights per year and the telescope has proven to be very reliable with a small amount of technical downtime. Comet monitoring --- For relatively bright comets (V < 12) we measure several times a week the gaseous production rates (using a Haser model) and the spatial distribution of several species among which OH, NH, CN, C2 and C3 as well as ions like CO+. The dust production rates (Afrho) and color of the dust are determined through four dust continuum bands (UC, BC, GC, RC). Such regular measurements are rare because of the lack of observing time on larger telescopes. Yet they are very valuable as they show how the gas production rate of each species evolves with respect to the distance to the Sun. Those observations allow to determine the composition of the comets and the chemical class to which they belong (rich or poor in carbon for instance [3]), possibly revealing the origin of those classes but also if there are some changes of the abundance ratios along the orbit (evolutionary effects). Indeed with half a dozen of comets observed each year --- and as long as possible along their orbit --- this program will provide a good statistical sample after a few years. We will present the results of this monitoring after three years of operations. Thanks to the way the telescope is operated, follow-up of split comets and of special outburst events is possible right after an alert is given and can bring important information on the nature of comets. In addition to providing the productions rates of the different species through a proper photometric calibration, image analysis can reveal coma features (jets, fans, tails), that can lead to the detection of active regions and measure the rotation period of the nucleus. The monitoring is also useful to assess the gas and dust activity of a given comet in order to prepare more detailed observations with larger telescopes. Such data can be obtained at any time under request. Finally a dozen of faint comets (V < 20) are monitored once a week through B, V, Rc, Ic filters and magnitudes and positions are sent to the MPC. [less ▲]

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See detailTRAPPIST monitoring of comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy)
Opitom, Cyrielle ULiege; Jehin, Emmanuel ULiege; Manfroid, Jean ULiege et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors - Book of Abstracts (2014, July 01)

We present the results of a dense photometric monitoring of comets C/2012 S1 (Ison) and C/2013 R1 (Lovejoy) using narrow-band cometary filters and the 60-cm TRAPPIST robotic telescope [1]. We were able to ... [more ▼]

We present the results of a dense photometric monitoring of comets C/2012 S1 (Ison) and C/2013 R1 (Lovejoy) using narrow-band cometary filters and the 60-cm TRAPPIST robotic telescope [1]. We were able to isolate the emission of the OH, NH, CN, C_2, and C_3 radicals for both comets as well as the dust continuum in four bands. By applying a Haser model [2] and fitting the observed profiles, we derive gas production rates. From the continuum bands, we computed the dust Afρ parameters [3]. We were able to follow the evolution of the gas and dust activity of these comets for weeks, looking for changes with the heliocentric distance, study the coma morphology, and analyze their composition and dust coma properties. Comet C/2012 S1 (ISON) was observed about three times a week from October 12 (r=1.43 au) to November 23, 2013. It was then at a heliocentric distance of 0.33 au, only five days before perihelion, when it disintegrated. This dense monitoring allowed us to detect fast changes of the cometary activity. We observed a slowly rising activity in October and early November, and two major outbursts around November 13 and November 19 [4], the gas and dust production rates being multiplied by at least a factor of five during each outburst and then slowly decreasing in the following days. These outbursts were correlated with changes in gas-production-rate ratios. The coma morphology study revealed strong jets in both gas and dust filters. Since the comet was very active in November, we were even able to detect OH jets in our images. Comet C/2013 R1 (Lovejoy) was observed before perihelion from September 9 (r=1.94 au) to November 16 (r=1.12 au), 2013 when the comet was too far North. We recovered the comet post-perihelion on February 13 (r=1.24 au), 2014 and planned to observe it until May (r=2.5 au) with narrow-band filters. We compare the evolution of gas and dust activity as well as the evolution of gas production rates ratios on both sides of perihelion. The morphological study of both gas and dust coma we already performed on pre-perihelion images revealed structures in gas and dust filters. We compare the gas and dust features in all filters and study their evolution. [less ▲]

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See detailHigh-resolution spectra of comet C/2013 R1 (Lovejoy)
Rousselot, P.; Decock, A.; Jehin, Emmanuel ULiege et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors - Book of Abstracts (2014, July 01)

Comet C/2013 R1 (Lovejoy) is a long-period comet discovered on 7 September 2013 by Terry Lovejoy with a 0.2-m telescope (Guido et al., 2013), it passed its perihelion (0.81 au) on 22 December 2013. It was ... [more ▼]

Comet C/2013 R1 (Lovejoy) is a long-period comet discovered on 7 September 2013 by Terry Lovejoy with a 0.2-m telescope (Guido et al., 2013), it passed its perihelion (0.81 au) on 22 December 2013. It was a bright comet visible to the naked eye. We obtained high-resolution spectra of this comet immediately after its perihelion passage during 4 nights in the period 23-26 December 2013. These spectra have been obtained with the 3.5-m Telescopio Nazionale Galileo (TNG) and the High Accuracy Radial velocity Planet Searcher in North hemisphere (HARPS-N) echelle spectrograph. HARPS-N is an echelle spectrograph covering the spectral range from 383 to 693 nm, with a spectral resolution of R=115000 (Cosentino et al., 2012). It is designed to measure stellar radial velocities in view of detecting extrasolar planets. Our observations are the first successful cometary observations performed with this instrument. They demonstrate that this spectrograph can also be efficient for getting cometary spectra, even if the sensitivity of this instrument is low in the blue part of its spectral coverage. We will present the results of our data analysis for these spectra. This analysis is focused on isotopic ratios, mainly ^{12}C/^{13}C with C_2 emission lines (with the method described in Rousselot et al. 2012) and ^{14}N/^{15}N with ^{14}NH_2 and ^{15}NH_2 emission lines (with the line wavelengths given in Rousselot et al. 2014), atomic oxygen emission lines at 557.7, 630.0 and 636.4 nm (intensity ratios and widths, see Decock et al. 2013) and relative production rates of the detected species. [less ▲]

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See detailInvestigation of the stellar content in the western part of the Carina nebula
Kumar, Brajesh; Sharma, Saurabh; Manfroid, Jean ULiege et al

in Astronomy and Astrophysics (2014), 567

Context. The low obscuration and proximity of the Carina nebula make it an ideal place to study the ongoing star formation process and impact of massive stars on low-mass stars in their surroundings. <BR ... [more ▼]

Context. The low obscuration and proximity of the Carina nebula make it an ideal place to study the ongoing star formation process and impact of massive stars on low-mass stars in their surroundings. <BR /> Aims: To investigate this process, we generated a new catalog of the pre-main-sequence stars in the Carina west (CrW) region and studied their nature and spatial distribution. We also determined various parameters (reddening, reddening law, age, mass), which are used further to estimate the initial mass function and K-band luminosity function for the region under study. <BR /> Methods: We obtained deep UBVRI Hα photometric data of the field situated to the west of the main Carina nebula and centered on WR 22. Medium-resolution optical spectroscopy of a subsample of X-ray selected objects along with archival data sets from Chandra, XMM-Newton and 2MASS surveys were used for the present study. Different sets of color-color and color-magnitude diagrams are used to determine reddening for the region and to identify young stellar objects (YSOs) and estimate their age and mass. <BR /> Results: Our spectroscopic results indicate that the majority of the X-ray sources are late spectral type stars. The region shows a large amount of differential reddening with minimum and maximum values of E(B - V) as 0.25 and 1.1 mag, respectively. Our analysis reveals that the total-to-selective absorption ratio R[SUB]V[/SUB] is ~3.7 ± 0.1, suggesting an abnormal grain size in the observed region. We identified 467 YSOs and studied their characteristics. The ages and masses of the 241 optically identified YSOs range from ~0.1 to 10 Myr and ~0.3 to 4.8 M[SUB]⊙[/SUB], respectively. However, the majority of them are younger than 1 Myr and have masses below 2 M[SUB]⊙[/SUB]. The high mass star WR 22 does not seem to have contributed to the formation of YSOs in the CrW region. The initial mass function slope, Γ, in this region is found to be -1.13 ± 0.20 in the mass range of 0.5 < M/M[SUB]⊙[/SUB] < 4.8. The K-band luminosity function slope (α) is also estimated as 0.31 ± 0.01. We also performed minimum spanning tree analysis of the YSOs in this region, which reveals that there are at least ten YSO cores associated with the molecular cloud, and that leads to an average core radius of 0.43 pc and a median branch length of 0.28 pc. Full Table 3 is only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/567/A109">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/567/A109</A> [less ▲]

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See detailThe shape and rotation of the tumbling asteroid (99942) Apophis
Scheirich, P.; Pravec, P.; Durech, J. et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors 2014 (2014, July 01)

Photometric observations of the asteroid (99942) Apophis taken from December 2012 to April 2013 revealed that it is in a non-principal axis rotation state. We constructed a numerical model of the asteroid ... [more ▼]

Photometric observations of the asteroid (99942) Apophis taken from December 2012 to April 2013 revealed that it is in a non-principal axis rotation state. We constructed a numerical model of the asteroid's shape and rotation. The asteroid is in a short-axis mode (SAM) of excited rotation. The precession and rotation periods are P_φ = 27.38 ± 0.07 h and P_ψ = 263 ± 6 h, respectively. The rotation is retrograde with the angular momentum vector's ecliptic longitude and latitude of 250° and -75° (the uncertainty area is approximately an ellipse with the major and minor semiaxes of 27° and 14°, respectively). The shape of the asteroid is dynamically close to a prolate ellipsoid, with the lengths of largest and intermediate axes of 1.64 ± 0.09 and 1.14^{+0.04}_{-0.08}, respectively (the shortest axis is normalized to unity); the largest and intermediate moments of inertia differ by 3-4 [less ▲]

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See detailDistant activity of comet C/2006 W3 (Christensen) as observed with Herschel
de Val-Borro, M.; Bockelée-Morvan, D.; Jehin, Emmanuel ULiege et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors - Book of Abstracts (2014, July 01)

We aimed to measure the H_2O and dust production rates in C/2006 W3 (Christensen) with the Herschel Space Observatory at a heliocentric distance of ˜ 5 au and compare these data with previous post ... [more ▼]

We aimed to measure the H_2O and dust production rates in C/2006 W3 (Christensen) with the Herschel Space Observatory at a heliocentric distance of ˜ 5 au and compare these data with previous post-perihelion Herschel and ground-based observations at ˜ 3.3 au from the Sun (Bockelée-Morvan et al. 2010b). We have searched for emission in the H_2O and NH_3 ground-state rotational transitions at 557 GHz and 572 GHz, simultaneously, toward comet C/2006 W3 (Christensen) with the Heterodyne Instrument for the Far Infrared (HIFI) onboard Herschel on UT 1.5 September 2010. Photometric observations of the dust coma in the 70 μ m to 160 μ m channels were acquired with the Photodetector Array Camera and Spectrometer (PACS) instrument on UT 26.5 August 2010. A tentative 4-σ H_2O line emission feature was found in the spectra obtained with the HIFI wide-band and high-resolution spectrometers, from which we derive a water production rate of 2.0(5)×10^{27} molec. s^{-1}. A 3-σ upper limit for the ammonia production rate of < 1.5×10^{27} molec. s^{-1} is obtained taking into account the contribution from all hyperfine components (Biver et al. 2012). The dust thermal emission was detected in the 70-μ m to 160-μ m filters, with a more extended emission in the blue channel. We fit the radial dependence of the surface brightness with radially symmetric profiles for the blue and red bands. The dust production rates, obtained for a dust size distribution index that explains the fluxes at the photocenters of the PACS images, lie in the range 70-110 kg s^{-1}. Scaling the CO production rate measured post-perihelion at 3.20-3.32 au, these values correspond to a dust-to-gas production rate ratio in the range 0.3-0.4. The blueshift of the water line detected by HIFI suggests preferential emission from the subsolar point. However, it is also possible that water sublimation occurs in small ice-bearing grains that are emitted from an active region on the nucleus surface at a speed of ˜ 0.2 km s^{-1}. The dust production rates derived in August 2010 are roughly one order of magnitude lower than in September 2009, suggesting that the dust-to-gas production rate ratio remained approximately constant during the period when the activity became increasingly dominated by CO outgassing. These data will complement available Herschel observations of the distant activity of other comets such as 29P/Schwassmann-Wachmann 1 (Bockelée-Morvan et al. 2010a) and main-belt comets 176P/LINEAR and P/2012 T1 (PANSTARRS) (de Val-Borro et al. 2012, O'Rourke et al. 2013). [less ▲]

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See detailPhase resolved X-ray spectroscopy of HDE 228766: Probing the wind of an extreme Of+/WNLha star
Rauw, Grégor ULiege; Mahy, Laurent; Nazé, Yaël ULiege et al

in Astronomy and Astrophysics (2014), 566

Context. HDE 228766 is a very massive binary system hosting a secondary component, which is probably in an intermediate evolutionary stage between an Of supergiant and an WN star. The wind of this star ... [more ▼]

Context. HDE 228766 is a very massive binary system hosting a secondary component, which is probably in an intermediate evolutionary stage between an Of supergiant and an WN star. The wind of this star collides with the wind of its O8 II companion, leading to relatively strong X-ray emission. <BR /> Aims: Measuring the orbital variations of the line-of-sight absorption toward the X-ray emission from the wind-wind interaction zone yields information on the wind densities of both stars. <BR /> Methods: X-ray spectra have been collected at three key orbital phases to probe the winds of both stars. Optical photometry has been gathered to set constraints on the orbital inclination of the system. <BR /> Results: The X-ray spectra reveal prominent variations of the intervening column density toward the X-ray emission zone, which are in line with the expectations for a wind-wind collision. We use a toy model to set constraints on the stellar wind parameters by attempting to reproduce the observed variations of the relative fluxes and wind optical depths at 1 keV. <BR /> Conclusions: The lack of strong optical eclipses sets an upper limit of ~ 68° on the orbital inclination. The analysis of the variations of the X-ray spectra suggests an inclination in the range 54-61° and indicates that the secondary wind momentum ratio exceeds that of the primary by at least a factor 5. Our models further suggest that the bulk of the X-ray emission arises from the innermost region of the wind interaction zone, which is from a region whose outer radius, as measured from the secondary star, lies between 0.5 and 1.5 times the orbital separation. Based on observations collected with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA), and on data collected at the San Pedro Mártir observatory (Mexico). [less ▲]

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See detailExtremely Organic-rich Coma of Comet C/2010 G2 (Hill) during its Outburst in 2012
Kawakita, Hideyo; Dello Russo, Neil; Vervack, Ron et al

in Astrophysical Journal (2014), 788

We performed high-dispersion near-infrared spectroscopic observations of comet C/2010 G2 (Hill) at 2.5 AU from the Sun using NIRSPEC (R ≈ 25,000) at the Keck II Telescope on UT 2012 January 9 and 10 ... [more ▼]

We performed high-dispersion near-infrared spectroscopic observations of comet C/2010 G2 (Hill) at 2.5 AU from the Sun using NIRSPEC (R ≈ 25,000) at the Keck II Telescope on UT 2012 January 9 and 10, about a week after an outburst had occurred. Over the two nights of our observations, prominent emission lines of CH[SUB]4[/SUB] and C[SUB]2[/SUB]H[SUB]6[/SUB], along with weaker emission lines of H[SUB]2[/SUB]O, HCN, CH[SUB]3[/SUB]OH, and CO were detected. The gas production rate of CO was comparable to that of H[SUB]2[/SUB]O during the outburst. The mixing ratios of CO, HCN, CH[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]6[/SUB], and CH[SUB]3[/SUB]OH with respect to H[SUB]2[/SUB]O were higher than those for normal comets by a factor of five or more. The enrichment of CO and CH[SUB]4[/SUB] in comet Hill suggests that the sublimation of these hypervolatiles sustained the outburst of the comet. Some fraction of water in the inner coma might exist as icy grains that were likely ejected from nucleus by the sublimation of hypervolatiles. Mixing ratios of volatiles in comet Hill are indicative of the interstellar heritage without significant alteration in the solar nebula. [less ▲]

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See detailL'astronomie dans le monde - 06/2014
Manfroid, Jean ULiege

Article for general public (2014)

Future lune ? - L'âge de la Lune - Des volcans actifs sur Vénus - Un lac dans le cratère Gusev ? - Météorites et atmosphère martiennes - L’hexagone de Saturne - Pluton - Exo-Terre - Bêta Pictoris b ... [more ▼]

Future lune ? - L'âge de la Lune - Des volcans actifs sur Vénus - Un lac dans le cratère Gusev ? - Météorites et atmosphère martiennes - L’hexagone de Saturne - Pluton - Exo-Terre - Bêta Pictoris b - Cérès et Vesta depuis Mars - Naine froide - Parallaxes par Hubble - L2 Puppis et le sort du Soleil - Supernova et lentille gravitationnelle - Champ magnétique galactique - L’objet de Sakurai - Fermi et la matière noire - Lentille naine [less ▲]

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See detailL'astronomie dans le monde - 05/2014
Manfroid, Jean ULiege

Article for general public (2014)

BICEP2; BOSS; Graines de trous noirs; El Gordo; Astéroïdes; Mercure; Encelade; Stardust

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See detailPlanètes et anneaux
Manfroid, Jean ULiege

Article for general public (2014)

La découverte des anneaux de Chariklo 30 ans après ceux de Neptune est l'occasion de passer en revue ces ornements du Système solaire

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See detailMeasurements of the 14N/15N isotopic ratio in comets's ammonia
Rousselot, P.; Pirali, O.; Jehin, Emmanuel ULiege et al

Conference (2014, May)

La détermination des rapports isotopiques de l'azote dans les différents objets du système solaire est importante pour une bonne compréhension de leur origine. Les mesures du rapport 14N/15N faites jusqu ... [more ▼]

La détermination des rapports isotopiques de l'azote dans les différents objets du système solaire est importante pour une bonne compréhension de leur origine. Les mesures du rapport 14N/15N faites jusqu'à présent ont montré une grande dispersion des valeurs (de 50 à 441), tous les objets du système solaire excepté Jupiter apparaissant enrichis en 15N comparés à la nébuleuse protosolaire. Différentes explications ont été proposées pour expliquer les valeurs observées, qui sont complexes à interpréter car dues non seulement au réservoir d'origine de l'azote d'où provient l'objet étudié mais également à des mécanismes de fractionnement isotopique. Le cas des comètes, dans ce contexte, est intéressant, car leur composition est supposée relativement proche de celle de la nébuleuse protosolaire et la seule valeur disponible jusqu'à l'année dernière, avait été calculée à partir de la molécule HCN et du radical CN (issu du HCN). Ce rapport était d'environ 150, bien en dessous de la valeur mesurée dans l'atmosphère terrestre (272). Les comètes contiennent beaucoup d'azote sous forme de NH3, photodissocié en NH2 dont les raies sont nombreuses dans le spectre visible. Il était donc possible de mesurer le rapport 14N/15N dans l'ammoniac pour vérifier l'influence possible de phénomènes de fractionnement isotopique entre le HCN et le NH3, ceci à condition de connaître avec précision les longueurs d'onde des raies de 15NH2. Pour déterminer ces longueurs d'onde, nous avons mesuré le spectre d'émission de la transition Ã2A1~X2B1 de 14NH2 et 15NH2 dans la gamme spectrale 5700 Å – 6000 Å sur la ligne AILES du synchrotron SOLEIL, avec un spectromètre par transformée de Fourier. L'analyse de ces spectres a permis, au final, la détection du 15NH2 dans les spectres cométaires et la première détermination du rapport 14N/15N dans l'ammoniac des comètes. [less ▲]

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See detailL'astronomie dans le monde - 04/2014
Manfroid, Jean ULiege

Article for general public (2014)

Cartographie d’une naine brune; 2006DP14; Anatomie d’un astéroïde; L’astéroïde P/2013 R3; Formation des planètes; Planètes Kepler; Bêta Pictoris; Cratère Mojave; Les astéroïdes de la ceinture principale ... [more ▼]

Cartographie d’une naine brune; 2006DP14; Anatomie d’un astéroïde; L’astéroïde P/2013 R3; Formation des planètes; Planètes Kepler; Bêta Pictoris; Cratère Mojave; Les astéroïdes de la ceinture principale; Planète X; Mercure et la gravitation; Gloire sur Vénus; Galaxies elliptiques massives; Cas A; SN 2014J et les supernovae Ia; Le Grand Nuage de Magellan; Nébuleuse d’Andromède; ESO 137-001 [less ▲]

Detailed reference viewed: 25 (2 ULiège)