Researchers believe that this result would have a significant impact on the return on Earth of samples of interplanetary rocks, given the interest of NASA for a human mission to an asteroid. Studies on the detection of such objects are in progress.

Image Caption : Simulation of the trajectory of an object captured by the Earth. The origin of the coordinate is the center of the Earth and the unit is the average Earth-Moon distance.]]> The images taken during this campaign are still under process as read our writing this lines them but we can already confirm that the outbursts appeared exactly at the predicted time! The level of the shower, initially predicted that has 600/hr based on past observations and reports, peaked at 300/hr, which is roughly 3 times the summer Perseids. This relative discrepancy is partly explained by the difference of data reduction methods used in the 30s and that defined by the international meteor organization (www.imo.net) in the 90s.

]]> Comet P/2011 W2 (Rinner) has been discovered with the robotic telescope MOSS (Moroccan Oukaimeden Sky Survey) located in the Oukaimeden ski resort in the High Atlas near Marrakech.

This observatory is the result of international cooperation between Claudine Rinner (owner of the telescope), Cadi Ayyad University of Marrakech (site owner) and the Société Jurassienne d'Astronomie(Owner of the dome)

This is not the first success of this collaboration. Last November it allowed the discovery of a near-Earth asteroid, 2011 VP 12. It is generally believed that we discover a Near-Earth asteroid every 100 objects discovered and a comet every 1000 objects!

It is also important to note that the discovery was made with a "small" 50cm diameter telescope compared with the major operations such as "PAN-STARRS" or LINEAR. The last time a French discovered a comet was in 1997. This was the comet Cll997J2 (Meunier-Dupouy).

Comet P/2011 W2 (RINNER) is part of the family of Jupiter, the comet will be not very bright seen from Earth and it never approach the Sun at less than 2.3 Astronomical Unit. She is currently at a magnitude of 17.6.

It will not even have a record of being the extraterrestrial object passed as close to us because on February 4, another tiny asteroid, 2011 CQ 1, is passed only at 5471km! It is true that he had a very modest size of barely one meter.]]>A very accurate timescale is needed to understand the geological events accompanying the Cretaceous and the disappearance of numerous species, such as dinosaurs. Cyclostratigraphic analysis and astronomical calibration, based on the identification in the sedimentary records of cycles controlled by the variations of the Earth's orbital parameters, provides precise estimates of duration and ages. This method have been used for the first time on the entire stage ending the Cretaceous, by a team of French (CNRS, IMCCE/Observatoire de Paris, Paris 6 University) and American researchers (Johns Hopkins University). The analysis of Upper Cretaceous deep sea marine sedimentary records from Indian and Atlantic Ocean, recovered during Ocean Drilling Program and Deep Sea Drilling Project oceanographic campaigns, associated to the new astronomical solution La2010, allowed the proposal of two ages for the Cretaceous-Paleogene boundary, at 65.59±0.07 Ma or 66±0.07 Ma. The second proposal is in better accordance with the last radio-isotopic dating, moving this boundary 405 000 years back in time from the current estimate.

D. Husson, B. Galbrun, J. Laskar, L. A. Hinnov, N. Thibault, S. Gardin and R. E. Locklair, 2011, Astronomical calibration of the Maastrichtian (late Cretaceous) (EPSL , sous presse)

J. Laskar, A. Fienga, M. Gastineau, H. Manche, 2011, La2010: A new orbital solution for the long term motion of the Earth, soumis à A&A (arXiv:1103.1084v1)

Nearby perigee moons are about 14% bigger and 30% brighter than lesser moons that occur on the apogee side of the Moon's orbit. Even a super perigee Moon is still 356,577 km away.

The best time to look is when the Moon is near the horizon. That is when illusion mixes with reality to produce a truly stunning view. For reasons not fully understood by astronomers or psychologists, low-hanging Moons look unnaturally large when they beam through trees, buildings and other foreground objects.]]> Our team was joined by two colleagues coming from the Czech Republic (P. Koten & D. Capek), as well as J.L. Rault who conducted very low-frequency radio observations. We did split into two teams: one at the Pic du Midi observatory and another one at the Guzet Neige ski resort, located 100 km west of the observatory. This allowed us to get our first double station meteors, which is the key point towards the computation of orbits, and hence the derivation of the origin of meteoroid stream.

caption of the image: a Geminids meteor as well as planet Venus rising above the French Pyrennees, during the IMCCE Geminids observation campaign in Guzet Neige (J. Vaubaillon, Canon Rebel XT, Sigma 30mm F/1.8, 4s). ]]> Recent observations of Venus in this spectral range have been conducted from the Centre d'Observation à Distance en Astronomie à Meudon (CODAM), using the NASA 3m telescope IRTF, located at Mauna Kea, Hawaii. The images and spectra of the dark side of Venus were obtained during consecutive nights (13, 14 and 15 December 2010), in excellent weather conditions. The image here enclosed shows the crescent of Venus (Figure 1). On the dark side we can see the cloud formations in the lower part of the atmosphere. These images will allow the study of atmospheric circulation on the planet. Corroborated with spectra obtained concomitant with these images, studies will focus on the molecular composition of the clouds and the atmospheric chemistry of deeper layers.

Figure 1. The crescent and the night side of Venus as it was observed in December 13, 2010. The black, vertical line in the center of the image is the slit of the spectrograph. On the night side of the planet we can distinguish several clouds in the low atmosphere (30-50km of altitude). These clouds are accessible mainly to the K filter (2.2-2.5 microns).

Credit : Eliot Young, Mark Bullock(SWRI), Mirel Birlan, Marcel Popescu(IMCCE)

Contact: Mirel Birlan (birlan@imcce.fr)]]> IMCCE, in collaboration with our Czech colleagues work under an observation campaign in order to calibrate the camera of the future CABERNET network (CAmeras for BEtter Resolution NETwork), which is part of the PODET project. ]]> Dry ice is solid CO2 jets are carrying chunks of snowy water ice along for the ride. However "it's snowing up, not down" !]]> Image: La comète Hartley 2. Credit: NASA/JPL-Caltech/UMD ]]> We provided here after the link towards those images, as well as pictures taken with a dslr-camera all summed up in a video file. This campaign was one of the last test before the complete installation of our high-resolution cameras, and is part of the PODET-MET project, partially supported by the city of Paris. The results are very encouraging, and the Perseids were beautiful as usual! The International meteor organization (IMO) reports a ZHR of 100 meteors per hour.

]]> The images show that Lutetia is heavily cratered, having suffered many impacts during its 4.5 billion years of existence. As Rosetta drew close, a giant bowl-shaped depression stretching across much of the asteroid rotated into view. The images confirm that Lutetia is an elongated body, with its longest side around 130km.

At closest approach, details down to a scale of 60 metres can be seen over the entire surface of Lutetia. ]]> The picture was taken only one hour before the close approach, at a distance of 80000 km with a resolution of 2km per pixel.]]> These convergent results are now completed by geophysical models of the evolution of asteroid parent body of the family of Themis. This family of objects has 550 members who are believed to come from the disruption of a parent body of approximately 450km in diameter. This body would have been differentiated with a solid core in the center inserted within a shell of dirty water ice (Castillo-Rogez and Schmidt, 2010). The double asteroid (90) Antiope, a member of the Themis family, whose components fit perfectly to the shape they would if they were like giant rotating fluid masses of 90 km in diameter, may actually house a large quantity of ice water under a solid surface layer.

Figure shows the infrared reflectance spectra of 24 Themis which are well fitted by a mixture of ice-coated pyroxene grains and amorphous carbon (Rivkin & Emery, Nature, 464). All spectra show an absorption band near 3,1 microns attibuted to fine-grained water ice as a frost deposited on regolith grains. ]]> Currently, the comet approaches the Sun. It shall reach its perihelion on July 2, and its magnitude will be close to 4 (Or even less if degassed near the Sun) in late June. At the same time, it will be circumpolar under northern latitudes. It can be found in the constellation Perseus until June 20.]]> This plan, entitled "Astronomy for the Developing World" would be realised, amongst other things, through the establishment of an Office for Astronomy Development. Towards the end of 2009 a call went out for potential hosts.

Early in 2010 South Africa was amongst 20 proposals from all over the world which reached the IAU. Today the big news of the selected host was announced - the IAU's International Office for Astronomy Development will be coming to Africa!! The office will be hosted at the headquarters of the South African Astronomical Observatory in Cape Town, a research facility of the National Research Foundation, and the Director will be selected from applicants from across the world.

The fact that this office is coming to Africa has great implications for the development of astronomy across the continent. In the spirit of the IAU's strategic plan this consequently has implications for the development of the continent in general! South Africa has always played a significant role amongst the developing world and is now being given the opportunity to host this prestigious office which has the potential to impact positively on all developing nations, in Africa and beyond. ]]> These bands encircle the globe of Jupiter. The famous Great Red Spot of Jupiter, a huge storm able to swallow Earth, bathed in the broad belt. It is now visible as the nose on your face. Surely a show not to be missed in a small telescope in late night light of dawn.

For now the mystery remains intact. Who will be the first to observe the return of the Great South Equatorial Belt ?]]> Hundreds of them, are discovered every day. They are so dark that they are almost undetectable from the ground. However, their very low temperature makes them very bright in the infrared. After only three months of operation, WISE has already identified a handful of potentially hazardous asteroids that cross Earth's orbit.

Project managers expect a final harvest of a hundred of these near-Earth asteroids by October 2010.]]> In the case of small bodies, there is a dichotomy between the asteroids that cross the orbit of the Earth and those of the Main Belt. The spectral response surfaces of a class of Near-Earth Asteroids (the taxonomic class Q) shows minerals whose physical properties are less affected by the space weathering(**). Mechanisms such as close approaches with the Earth, Mars or Venus, or collisions with other small asteroids are proposed to produce the re-surfacing of Near-Earth Asteroids.

A French-American team examined the issue of proximity between NEOs and the terrestrial planets. The spectra of a sample of one hundred asteroids have been analyzed and the results were corroborated with their orbital dynamics.

The conclusion of this research is that the Earth can produce a significant impact for the re-surfacing processes, if the asteroid passes at least a distance of 16 Earth radii from the planet. This distance is approximately one quarter of the Earth-Moon distance. Seismic waves generated by the close passage are able to "shake up" the surface of the object so that rocks and regoliths are reorganizing. The reorganization of the surface of the asteroid is revealed by the spectral measurements. Having suffered less exposure to space weather, minerals resulting from the re-surfacing will show spectra which are in better agreement with laboratory spectra of ordinary chondrite meteorites.

In 2029, the asteroid 99942 Apophis, whose diameter is estimated at about 270 meters, will pass close to Earth. This passage will take place at a distance of about 42,000 km and will not affect our planet. However, during this close passage, the asteroid will be located inside the perimeter of the theoretical limit discussed above, and vibrations will be strong enough to produce its re-surfacing. Spectroscopic observations of the close approach of 99942 Apophis will be possible in 2029, will confirm these assumptions and will contribute to the validation of these results.

(*) Space weather includes several factors such as the solar wind, the cosmic rays, and the impacts with micro-meteoroids.
(**) The spectrum of Q-type asteroids is the best analogue for most meteorites that exist in collections (ordinary chondrite meteorites).

French team: Francesca DeMeo, Sihane Merouane (Observatoire de Paris), Alessandro Morbidelli (Observatoire de la Cote d'Azur), Pierre Vernazza (ESTEC and Observatoire de Paris), Richard Binzel (MIT IMCCE, Observatoire de Paris), Mirel Birlan (IMCCE, CNRS 8028, Observatoire de Paris).

Contact: Mirel Birlan (email : Mirel.Birlan@imcce.fr)]]> The shape is probably due to an effect of resurfacing due to the YORP effect. This effect is due to asymmetrical reradiating of solar radiation by any body of irregular shape. A particularly imposing equatorial bulge contributes to the appearance of diamond. YORP spin-up could have caused landsliding of mid-latitude surface material towards the equatorial bulge. ]]> Un calendrier perpétuel qui est basé sur la lunaison moyenne, il alterne six mois de 30 jours et six mois de 29 jours pour les années communes de 354 jours et sept mois de 30 jours et cinq mois de 29 jours pour les années abondantes de 355 jours (les deux derniers mois ayant 30 jours). Onze années abondantes sont judicieusement réparties sur une période de trente ans parmi dix-neuf années communes. Ce calendrier suit remarquablement bien la lunaison moyenne. En effet, il se décale d'un jour par rapport à la lunaison moyenne au bout de 30902 lunaisons soit environ 2575 années lunaires. Le jour calendaire commence le soir au crépuscule.

Un calendrier religieux qui est basé sur l'observation du premier croissant de Lune. Ce calendrier est par nature local, car les conditions d'observation dépendent du lieu d'observation et de l'époque à laquelle l'observation a lieu. Ainsi les premiers croissants de Lune sont difficilement observables dans l'hémisphère nord aux fortes latitudes pour les lunaisons proches de l'équinoxe d'automne alors qu'elles sont facilement observables dans l'hémisphère sud à la même époque. On a le phénomène inverse au voisinage de l'équinoxe de printemps. La longueur du mois ne pouvant avoir plus de trente jours, la nuit commençant au soir du 29e jour est la nuit du doute. Si le croissant est visible, le mois finissant a 29 jours et le nouveau mois commence le soir même. Si le croissant n'est pas visible, le mois finissant a 30 jours et le mois suivant commence le lendemain soir. Le début du mois de rang n dépend donc du début du mois de rang n°1. La prédiction du début et de la fin du mois de jeûne de Ramadan s'appuie sur ce principe et sur des critères de visibilité du premier croissant.

Finalement c'est l'autorité religieuse, le Conseil Français du Culte Musulman, qui décide des dates du début et de fin des mois en s'appuyant sur les prédictions de visibilité ou sur la visibilité effective du croissant.

En 2009 les deux croissants de Lune, correspondant au début et à la fin du mois de Ramadan de l'an 1430 de l'Hégire, seront visibles en France métropolitaine deux jours après les nouvelles Lunes d'août et de septembre : le soir du 22 août et le soir du 20 septembre 2009. L'observation du 21 août sera possible uniquement dans le sud du pays avec des aides optiques et deviendra de plus en plus difficile au fur et à mesure que les villes seront situées plus au nord. De même l'observation du 20 septembre à l'oeil nu ne sera possible que dans le sud de la France et nécessitera une aide optique au fur et à mesure que l'on montera en latitude.]]> http://www.imcce.fr/fr/actualites/index.php?id=2016 Dans l´hémisphère nord le solstice d´été correspond à l´instant où la longitude apparente du Soleil est égale à 90 degrés et il marque l´entrée dans cette saison. Notre calendrier (le calendrier grégorien) est construit de manière à rester proche d´une date fixe pour le début des saisons. La date du solstice d´été en 2009 est le 21 juin à 5h 45min 32s UTC soit à 7h 45min 32s TLF (temps légal français). Dans le calendrier grégorien créé en 1582, le solstice d´été peut survenir le 19, 20, 21 ou 22 juin. Il est survenu un 20 juin en 1896 et il tombe à nouveau à cette date en 2008. Il est survenu un 22 juin en 1975 et tombera à nouveau à cette date en 2203, 2207, 2211 et 2215 puis en 2302. Le solstice d´été tombera un 19 juin en 2488 et ce sera la première fois depuis la création du calendrier grégorien. Au XXe siècle les solstice d'été sont tombés exclusivement le 21 juin (64) et le 22 juin (36) alors qu'au XXIe siècle le solstice d'été tombera exclusivement le 20 juin (47) et le 21 juin (53). Le jour du solstice d´été, le Soleil passe à midi au zénith du tropique du Cancer. Plus au nord ce phénomène ne se produit jamais. C´est le jour où pour un lieu donné de l´hémisphère nord, la durée du jour est maximum. Le solstice d´été dans l´hémisphère nord correspond au solstice d´hiver dans l´hémisphère sud. 2009-06-17http://www.imcce.fr/fr/actualites/index.php?id=2015

En 2009, le jour où le Soleil passe au plus proche du zénith est le 27 mai à 9h 17m 51s UTC, il suffit d'observer la direction du Soleil à cet instant pour avoir la direction de la Mecque. C'est également valable pour les deux jours au voisinage de cette date.
On remarquera qu'après cette date le Soleil culmine au nord. ]]>http://www.imcce.fr/fr/actualites/index.php?id=2014 Why the materials constituting the surface of the asteroids reflect in a different way the light when they are in space or in laboratory, appearing thus redder and darker in space? This different behavior is mainly due to the interaction of the interplanetary medium with the surface of the asteroids. This surface is deteriorated by the solar wind and the micrometeorites present in the interplanetary medium.

This team studied young families of asteroids formed from violent collisions and having thus a young surface. These asteroids submitted to the impacts of the interplanetary medium see their surface evolving very quickly, in approximately 1 million years, to arrive at surfaces having average colors identical to those of old asteroids. This rapid evolution supports the role of the solar wind as principal element in the transformation of their surfaces. The composition plays also a part, the asteroids including olivine evolving more quickly.

Figure 1 : Evolution of the color of asteroids as a function of their age, assuming that these objects have the same composition. The initial color of an asteroid when it has just undergone a catastrophic collision (which breaks it up into various fragments) should be similar to the color of the meteorites measured in laboratory. The observation of young asteroids (age < 1 million years) reveals that their color has been strongly modified in this short time, giving them the appearance of old surfaces. Only the solar wind (red arrow) can act so quickly on their color, as demonstrated by laboratory experiments. In a second time, micrometeorites impacts could age surfaces with a longer time scale. © Nature.

This team was also interested in the asteroids crossing the orbit of the Earth (NEA: Near-Earth Asteroids) which for some have a color which reveals a surface virgin of any deterioration. All these objects were formed by collisions since more than 100 million years. Thus, recent collisions cannot explain their apparent youth and it is necessary to find another process being able to renovate the matter on the surface. These asteroids could undergo gravitational effects with the approach of the Earth or another telluric planet (tidal effects) tending to dredge up on the surface the internal material, which was not exposed to the solar wind and thus to give this effect of ~renovation~. It will be necessary to confirm this hypothesis in observing the spectral color of the asteroids of the same type present in the principal belt, between Mars and Jupiter, which should then be redder. Reference

Solar wind as the origin of rapid reddening of asteroid surfaces
P. Vernazza, R. P. Binzel, A. Rossi, M. Fulchignoni & M. Birlan
Nature 23/04/2009.

Contact

Pierre Vernazza (ESA, et Observatoire de Paris, LESIA)
Marcello Fulchignoni (Observatoire de Paris, LESIA, et Paris VII)
Mirel Birlan (Observatoire de Paris, IMCCE, et CNRS)
]]>http://www.imcce.fr/fr/actualites/index.php?id=2012 However the azimuth of the axis is not perfectly orientated East-West, it deviates from approximately 22° what changes considerably the dates when this phenomenon is observable. The altitude of the floor in front of the frontage of the palace of Versailles turned towards the Grand canal is 142m. The horizon in the direction of the Grand canal is heightened because of a hill of 128 meters altitude, located at 10650 meters.

The azimuth of the axis of the Grand canal is 111°49' 56 " , thus approximately 111°50 '; (approximately 292 ° northern). Taking into account the atmospheric refraction and these various parameters, we calculated that the center of the Sun lies down in 2008 in the axis of the Grand canal at the following dates:

Sunset in the axis of the Grand Canal	Hour of sunset (TLF)*	Azimuth
The 26th april 2009	20h 55min 26s	111° 22' 58"
The 27th april 2009	20h 56min 54s	111° 53' 14"
The 28th april 2009	20h 58min 21s	112° 23' 11"
* TLF = French legal time

More details:
Be cautious: if the horizon is badly estimated, these results can be shifted by one day or two. The same if one goes up in altitude, for example if one observes from the first floor of the castle, the results can also be shifted by one day.

Moreover these calculations were made with a certain value of the horizontal atmospheric refraction, but the refraction varies with the atmospheric conditions (pressure, temperature...) the times of the sunsets can thus vary slightly with respect to the predicted values.

We gave these values to the nearest second of time but it is only the internal precision of calculation, the precision of the prediction, taking into account the uncertainties on the refraction, is about one minute of time.

If one studies the data above, one notes that the azimuth of the center of the Sun at sunset never falls exactly into the axis from the channel, it is close to this axis for the median dates (on April 27 and on August 14), it is slightly to the south (towards the left) when the azimuth is lower than 111°49' 56 "and slightly to the north (towards the right) when the azimuth is higher than 111°49' 56".

In all the cases it is possible to take a photograph in the axis of the Grand canal but the center of the Sun will be more or less high with respect to the horizon. One can also exploit the height of the observer while going down or while going up compared to the terrace of the frontage. If one goes up, the center of the Sun will be higher, if one goes down, the center of the Sun will be lower.

Caution: If the Sun at sunset dazzles you, do not look at it directly: it is still too high on the horizon. In this case prevent photographing it without filter, you are likely to damage your camera and your sight if you use an apparatus with a reflex optics. ]]>http://www.imcce.fr/fr/actualites/index.php?id=188 How could a Paris Observatory team measure this asteroid, which passed the opposite side of the Earth, soaring over Tahiti? A special facility of the Observatory, the Centre d'Observation à Distance en Astronomie à Meudon (CODAM) allowed the Paris team to command the 3 metre diameter telescope IRTF, a highly specialized telescope located at Mauna Kea, Hawaii. From Meudon, the Paris team was able to use the Hawaii telescope to track down the space intruder and capture its light into the telescope's near-infrared spectrograph, SpeX.

The resulting spectral colors, measured over the infrared wavelengths 0.8-2.5 micron, revealed characteristic signatures of the minerals olivine and pyroxene (commonly found in both meteorites and Earth rocks), placing the asteroid into a category that astronomers refer to as the S-class. By knowing this class, the team can associate 2009 DD45 with other small S-class asteroids which have measured values for their reflectivity; about 36% of the sunlight hitting the asteroid is reflected (results from Delbo et al. 2003, Icarus 166, 116).From the brightness of the asteroid, and its reflectivity, the Paris team could deduce the mean diameter to be 19 +/- 4 meters.

Contact persons:

Richard Binzel (Massachusetts Institute of Technology, invited researcher LESIA, IMCCE, Observatoire de Paris)

Francesca DeMeo (LESIA, Observatoire de Paris)

Mirel Birlan (IMCCE, Observatoire de Paris)]]>http://www.imcce.fr/fr/actualites/index.php?id=187 in the night on March 28th to 29th 2009, at 2a.m. it will be 3a.m. ]]>http://www.imcce.fr/fr/actualites/index.php?id=186 Gregorian calendar) is built so as to preserve a fixed date for the seasons beginning. The date of spring equinox is, in 2008, March 20th, at 11h 44min UTC (12h44min Paris standard time).

Since creation of the Gregorian calendar (1582) the spring equinox is on March 19th, 20th or 21th. At XIXth and XXth centuries it always is on March 20th or 21th. In the past, it was on March 19th in 1652, 1656, 1660, 1664, 1668, 1672, 1676, 1680, 1684, 1685, 1688, 1689, 1692, 1693, 1696, 1697, 1780, 1784, 1788, 1792 and 1796. It will again fall on March 19th in 2044. At the equinox day, if we ignore atmospheric refraction, duration of the night is equal to the duration of the day. It is also the day when Sun rises full East and lie down full West. The spring equinox in the Northern hemisphere corresponds to the autumn equinox in the Southern hemisphere. ]]>http://www.imcce.fr/fr/actualites/index.php?id=185
Cette comète va passer à 0,4 UA de la Terre le 24 février 2009, elle aura alors une magnitude proche de 5 et sera donc visible à l'oeil nu. La meilleur période d'observation est centrée sur cette date qui correspond à la fois à son opposition et à la nouvelle Lune. Elle sera alors observable toute la nuit dans la constellation du Lion. L'observation sera facilitée par l'utilisation de jumelle. Elle restera visible durant le printemps. Comme son orbite est proche de l'écliptique, une anti-queue, composée de poussière éjectée par la comète, sera visible. ]]>http://www.imcce.fr/fr/actualites/index.php?id=184 Le tableau ci-dessous fournit les dates et instants de prises de vue du Soleil dans l'axe de l'arche de l'Arc de Triomphe depuis le square de la Porte Maillot. Les instants sont en Temps universel. Ajouter une heure pour avoir l'heure légale en France métropolitaine.
ATTENTION : même à faible altitude l'observation directe du Soleil peut être dangereuse pour la vue (et pour votre appareil photo). Pour les photos, il y a risque de surexposition, pensez à prendre un filtre si votre appareil photo ne permet pas de faire de très courtes expositions.

Jour	Instant du lever du centre du Soleil (UTC)	Période où le centre du Soleil passe par l'axe de l'arche (UTC)	Variation de la hauteur du centre du Soleil durant cette période (UTC)
04/02	7h 25m 02s	7h 26m 18s à 7h26m 38s	9' 52" à 12' 29"
05/02	7h 23m 31s	7h 27m 22s à 7h 27m 42s	30' 20" à 33' 00"
06/02	7h 21m 59s	7h 28m 26s à 7h 28m 46s	51' 29" à 54' 11"
07/02	7h 20m 25s	7h 29m 30s à 7h 29m 50s	1° 13' 16" à 1° 16' 00"

]]>http://www.imcce.fr/fr/actualites/index.php?id=183 http://www.imcce.fr/en/actualites/index.php?id=171 2008-07-31 http://www.imcce.fr/en/actualites/index.php?id=167 2008-07-17 This partial eclipse by the umbra will be visible partly from France, starting from the begining of the umbra till the end of the penumbra. Only the begining of the penumbra will not be visible. This table give the general circumstances of this eclipse. Time is given in Coordinated Universal Time (add 2 hours to get the French legal time). http://www.imcce.fr/en/actualites/index.php?id=168 2008-07-17 One reads sometimes in some journals that the axes of the Grand canal of the palace of Versailles are orientated East-West and North-South. Some deduced, with good reason, that the Sun was to lie down in the axis of the Grand canal at the equinoxes. However the azimuth of the axis is not perfectly orientated East-West, it deviates from approximately 22° what changes considerably the dates when this phenomenon is observable. The altitude of the floor in front of the frontage of the palace of Versailles turned towards the Grand canal is 142m. The horizon in the direction of the Grand canal is heightened because of a hill of 128 meters altitude, located at 10650 meters. The azimuth of the axis of the Grand canal is 111°49' 56 " , thus approximately 111°50 '; (approximately 292 ° northern). Taking into account the atmospheric refraction and these various parameters, we calculated that the center of the Sun lies down in 2008 in the axis of the Grand canal at the following dates: Sunset in the axis of the Grand Canal Hour of sunset (TLF)*Azimuth The 13th August 2008 21h 5m 14s112° 18' 24" The 14th August2008 21h 3m 28s111° 48' 54" The 15th August 2008 21h 1m 40s111° 19' 08" * TLF = French legal time More details: Be cautious: if the horizon is badly estimated, these results can be shifted by one day or two. The same if one goes up in altitude, for example if one observes from the first floor of the castle, the results can also be shifted by one day. Moreover these calculations were made with a certain value of the horizontal atmospheric refraction, but the refraction varies with the atmospheric conditions (pressure, temperature...) the times of the sunsets can thus vary slightly with respect to the predicted values. We gave these values to the nearest second of time but it is only the internal precision of calculation, the precision of the prediction, taking into account the uncertainties on the refraction, is about one minute of time. If one studies the data above, one notes that the azimuth of the center of the Sun at sunset never falls exactly into the axis from the channel, it is close to this axis for the median dates (on April 27 and on August 14), it is slightly to the south (towards the left) when the azimuth is lower than 111°49' 56 "and slightly to the north (towards the right) when the azimuth is higher than 111°49' 56". In all the cases it is possible to take a photograph in the axis of the Grand canal but the center of the Sun will be more or less high with respect to the horizon. One can also exploit the height of the observer while going down or while going up compared to the terrace of the frontage. If one goes up, the center of the Sun will be higher, if one goes down, the center of the Sun will be lower. Caution: If the Sun at sunset dazzles you, do not look at it directly: it is still too high on the horizon. In this case prevent photographing it without filter, you are likely to damage your camera and your sight if you use an apparatus with a reflex optics. http://www.imcce.fr/en/actualites/index.php?id=169 2008-07-17 Each year in May, photographing the Sun lying down under the arc of Triumphal arch is possible. When we are at the right distance from the Triumphal Arch, the apparent diameter of the arch is equal to the apparent diameter of the Sun. For sunset, two specific locations are in general chosen, Place de la Concorde and Place Clemenceau. As seen from Place de la Concorde the apparent diameter of the arch is a little too small. The Sun, too large, is very slightly masked by the arch, but we benefit from a photograph catching the whole Champs-élysées. On the other hand, the second position, from Place Clemenceau, gives an apparent diameter of the arch nearly identical to the apparent diameter of Sun. It will be possible to photograph the Sun from the Rond-point des Champs-élysées Clemenceau on August 2nd, 3rd and 4th at the evening. <p><center> <table class= " TB1 " > <thead> <tr valign= " signal " > <td align= " center " >Dates</td> <td align= " center " >Sunset at Paris</td> </thead> <tbody> <tr> <td class= " TB1 " >&nbsp;&nbsp; August 2nd 2008</td> <td class= " TB1 " >&nbsp;&nbsp; at 21h 18,9m standard time</td> </tr> <tr> <td class= " TB1 " > &nbsp;&nbsp; August 3rd 2008</td> <td class= " TB1 " >&nbsp;&nbsp; at 21h 17,4m standard time</td> </tr> <tr> <td class= " TB1 " >&nbsp;&nbsp;August 4th 2008</td> <td class= " TB1 " >&nbsp;&nbsp; at 21h 15,9m standard time</td> </tr> </tbody> </table></center> http://www.imcce.fr/en/actualites/index.php?id=170 2008-07-17 For France in 2008, the two crescents of the Moon will be visible in metropolitan France two days after the new Moons on August and September, at evening on September 1st and at evening on October 1st . The observation on September 1st will be possible with the help of optics and will be more difficult when the observer will be higher in the North. Possible observation with naked eye will occur only under optimum conditions. http://www.imcce.fr/en/actualites/index.php?id=166 2008-07-02 The orbit of the Earth-Moon barycentre around the Sun is, at first approximation, an ellipse. The Earth-Sun distance is not constant and presents a minimum <a href="#pericentre" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#pericentre','','scrollbars=yes,resizable=yes,width=580,height=600')" class="lien">(perihelion)</a> and a maximum <a href="#apocentre" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#apocentre','','scrollbars=yes,resizable=yes,width=580,height=600')" class="lien">(aphelion)</a>. The Earth will pass to its aphelion on July 4th, 2008 at 7h 40min 54s UTC. The Earth-Sun distance will be then of 1,016753512046ua is exactly 152,104160419735Mkm . This maximum value is not the same year after year because the Earth orbit is not a perfect ellipse but an ellipse perturbed by the gravitational effects. It can appear paradoxical that this maximum distance from the Sun is reached whereas we are in summer and the weather is hot in our hemisphere. This is due to the inclination of the rotation axis of the Earth with respect to the perpendicular of its orbit plan (the ecliptic). At the summer solstice (on June 20th in 2008), a date close to the passage of the Earth at aphelion, the Sun passes to the zenith of the tropic of Cancer. In Northern hemisphere the elevation of the Sun on the horizon and the duration of its illumination are then maximum. This effect contributes more to the climate than the distance to the Sun. The seasons are reversed between Northern hemisphere and Southern hemisphere. However it is false to believe that for our hemisphere, the fact that the Earth is at aphelion in summer and at perihelion in winter (towards January the 4th) would moderate the contrast of the seasons then would amplify it in southern hemisphere. It is also erroneous of saying that the day of the summer solstice is the day when the Sun culminates with its higher elevation in the Northern hemisphere! That is true only for the places located at the North of the Cancer tropic. The date of passage of the Earth in perihelion and that of passage in aphelion advance in our calendar. In this way in approximately 9.800 years, the Earth will pass in perihelion on June 21th at the time of the summer solstice. http://www.imcce.fr/en/actualites/index.php?id=165 2008-06-10 In the northern hemisphere the summer solstice corresponds to the date when the apparent longitude of the Sun is equal to 90 degrees and it marks the beginning of this season. Our calendar (the Gregorian calendar) is built so as to remain close to a fixed date for the beginning of the seasons. The date of summer solstice in 2008 is on June 20th at 23h 59min UTC. In the Gregorian calendar created in 1582, the summer solstice can occur on June 19th, 20th, 21th or 22th. It occurred on June 20th in 1896 and fall again on this date in 2008. It occurred on June 22th in 1975 and will fall again on this date in 2203, 2207, 2211 and 2215 then in 2302. The summer solstice will fall on June 19th in 2488 and it will be the first time since the creation of Gregorian calendar. On the day of the summer solstice, for an observer located on the tropic of Cancer, the direction of the Sun points toward the zenith at twelve o'clock. Farther to the North this phenomenon never occurs. The day of solstice is the day when for a given location of the Northern hemisphere, the duration of the day is maximum. The summer solstice in the Northern hemisphere corresponds to the winter solstice in the Southern hemisphere. http://www.imcce.fr/en/actualites/index.php?id=163 2008-06-02 The IMCCE scientific and technical Note S093 ''Some uncompleted problems of newtonian and relativistic celestial mechanics'' is published. In that note V.A. Brumberg makes a review of some problems of Newtonian and relativistic celestial mechanics to be regarded as uncompleted problems worthy of further investigation. These problems include : <p>- the construction of general solution of the three-body problem by means of the series of polynomials, <p>- the construction of theories of motion using the fast converging elliptic function expansions, <p>- the representation of the rotation of the planets in the form compatible with the general planetary theory, <p>- the relativistic extansion of the newtonian theories of motion and rotation, - the simplification of relativistic celestial mechanics and astrometry in the post--Newtonian approximation by using the linearized metric of general relativity, <p>- the motion of the solar system bodies at the cosmological background. http://www.imcce.fr/en/actualites/index.php?id=164 2008-06-02 V.A. Brumberg has improved and updated his lectures on relativity in celestial mechanics and astrometry. The aim of these lectures is to prepare students for work in the field of relativistic celestial mechanics and aastrometry. They can be found on the website of the IMCCE to the rubric ''Courses of Astronomy''. http://www.imcce.fr/en/actualites/index.php?id=162 2008-05-05 Each year in May, it is possible to photograph the Sun lying down under the arc of Triumphal arch. When we place at the good distance compared to the Triumphal Arch, the apparent diameter of the arch is equal to apparent diameter of Sun.<br> For sunset, two particular locations in general are chosen, the Place de la Concorde ans the Place Clémenceau. Seen since the Place de la Concorde the apparent diameter of the arch is a little too small, the Sun, too much large, is very slightly masked by the arch, but we benefit from a photograph tallied on the whole of the Champs-élysées. On the other hand to height of the Place Clémenceau, the second position gives apparent diameter of the arch quasi-identical to the apparent diameter of Sun.<br> It will be possible to photograph the Sun since the place de la Concorde on May 6th and 7th at the evening, since the Place Clémenceau on May 7th, 8th and 9th. Be careful before May 8th the arch contains a large three color flag in seen commemoration of May 8th. <p><center> <table class= " TB1 " > <thead> <tr valign= " signal " > <td align= " center " >Dates</td> <td align= " center " >Sunset at Paris</td> </thead> <tbody> <tr> <td class= " TB1 " >&nbsp;&nbsp; May 7th 2008</td> <td class= " TB1 " >&nbsp;&nbsp; at 21h 14m standard time</td> </tr> <tr> <td class= " TB1 " > &nbsp;&nbsp; May 8th 2008</td> <td class= " TB1 " >&nbsp;&nbsp; at 21h 15m standard time</td> </tr> <tr> <td class= " TB1 " >&nbsp;&nbsp;May 9th 2008</td> <td class= " TB1 " >&nbsp;&nbsp; at 21h 16m standard time</td> </tr> </tbody> </table></center> http://www.imcce.fr/en/actualites/index.php?id=158 2008-02-25 In accordance with the decree of April 3rd, 2001 of the Ministry for the economy, Finances and of Industry, relating to the French standard time, the period from summer time for the year 2008 begins last Sunday from March to 2a.m. morning. Therefore, <span class="textebold">in the night on March 29th to 30th 2008, at 2a.m. it will be 3a.m. </span> http://www.imcce.fr/en/actualites/index.php?id=159 2008-02-25 In the Northern hemisphere, the spring equinox corresponds to the moment when apparent longitude of the Sun is equal to 0 degree (the direction of the Sun is then that of the gamma point, origin of celestial longitudes). Our calendar (the <a href="#gregorian_ca" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#gregorian_ca','','scrollbars=yes,resizable=yes,width=582,height=600')" class="lien">Gregorian calendar</a>) is built so as to preserve a fixed date for the seasons beginning. The date of spring equinox is, in 2008, <span class = "textebold">March 20th, at 5h 48min UTC (6h48min Paris standard time).</span> <P>Since creation of the Gregorian calendar (1582) the spring equinox is on March 19th, 20th or 21th. At XIXth and XXth centuries it always is on March 20th or 21th. In the past, it was on March 19th in 1652, 1656, 1660, 1664, 1668, 1672, 1676, 1680, 1684, 1685, 1688, 1689, 1692, 1693, 1696, 1697, 1780, 1784, 1788, 1792 and 1796. It will again fall on March 19th in 2044. At the equinox day, if we ignore atmospheric refraction, duration of the night is equal to the duration of the day. It is also the day when Sun rises full East and lie down full West. The spring equinox in the Northern hemisphere corresponds to the autumn equinox in the Southern hemisphere. http://www.imcce.fr/en/actualites/index.php?id=160 2008-02-25 One reads sometimes in certain reviews that the axes of the Large Channel of the Castle of Versailles are directed East-West and North-South. Some in it is deduced, with good reason, that the Sun was to lie down in the axis of the large channel the days of the equinoxes. However the azimuth of the axis is not perfectly East-West, it deviates some from approximately 22° what changes the dates considerably where this phenomenon is observable. The altitude of the floor in front of the frontage of the castle of Versailles turned towards the Large Channel is of 142m, the horizon in the direction of the large channel elevated because of a hill of 128 meters altitude is located at 10650 meters. The azimuth of the axis of the Large Channel is of 111°49' 56 "is approximately 111°50 '; (approximately 292 ° northern). By holding account of the atmospheric refraction and these various parameters we calculated that the center of the Sun lies down in 2005 in the axis of the large channel at the following dates:<p> <table class="texte" border="1" align=center> <tr align=center><td>Sunset in the axis of the Grand Canal</td> <td>Hour of sunset (TLF)*</td><td>Azimuth</td></tr> <tr align=center><td> The 26th April 2007</td><td> 20h 54min 16s</td><td>111° 02' 39"</td></tr><tr align=center><td> The 27th April2007</td><td> 20h 55min 44s</td><td>111° 33' 02"</td></tr><tr align=center><td> The 28th April 2007</td><td> 20h 57min 11s</td><td>112° 03' 06"</td></tr> <tr align=right><td colspan=3>* TLF = French legal time</td></tr> </table> <p> <span class="textebold">Some precise details:</span><br> If the horizon were badly estimated these results can be shifted one day or two. The same if one goes up in altitude, for example, if one observes since the first stage of the castle, the results can also shift one day. It would be advisable to take photographs to check these forecasts. Moreover these calculations were made with a certain value of the horizontal atmospheric refraction, but the refraction varies with the atmospheric conditions (pressure, temperature...) the moments of sleeping can thus vary slightly compared to the predicted values. We gave these values to the second of time near but it is only the internal precision of calculation, the precision of the prediction counts held of uncertainties on the refraction is of about a minute of time.<p> If one studies the data above one notes that the azimuth of the center of the Sun to its sleeping never falls exactly into the axis from the channel, it is nearest for the median dates (on April 27 and on August 15), it is slightly in the south (towards the left) when the azimuth is lower than 111°49' 56 "and slightly in north (towards the line) when the azimuth is higher than 111°49' 56". In all the cases it is possible to take a photograph in the axis of the large channel but the center of the Sun will be more or less high compared to the horizon. One can also exploit the height of the observer while going down or while rising compared to the terrace of the frontage. If one goes up, the center of the Sun will be higher, if one goes down, the center of the Sun will be lower.<p> <span class="codered">Caution:</span> <br>If the Sun with its sleeping dazzles you, do not look at it directly, it is that it is still too high on the horizon. In this case prevent photographing it without filter, you are likely to damage your camera and your sight if you use an apparatus with aiming reflex. http://www.imcce.fr/en/actualites/index.php?id=150 2007-12-06 This diary is original in its kind! In addition to a traditional diary, it is the daily tool of all the astronomers amateurs or all those who have a passion for the world of astronomy. Every day we can know what are the great space projects, who is Leon Foucault or when the next Moon eclipses occur...<br> Richly illustrated and equipped with many star maps, it is a practical tool, learned... and which makes dreaming!<br> Size 15x21. 154 pages. This diary is available on library and at followind address : <p> <table class="texte2"> <tr> <td> <p><span class="textebold">" Agenda Astronomique 2008"<br> </span><a href="http://livres.edpsciences.org/ouvrage.php?ISBN=9782759800261" target="_blank" class="lien">Éditeur : EDP Sciences </a><br>7 Avenue du Hoggar<br>Z.I. de Courtaboeuf<BR>B.P. 112<br>F-91944 LES ULIS Cedex A<br>176 pages<br>Price: 12&nbsp;euros <br> ISBN : 978-2-7598-0026-1<br></p></td></tr> </table> http://www.imcce.fr/en/actualites/index.php?id=151 2007-12-06 The <i>Guide de Données Astronomiques 2008 pour l'observation du ciel-Annuaire du Bureau des Longitudes</i> has just appeared to the EDP Sciences editor. These annual ephemerides, elaborated by the Institute de Mécanique Céleste et de Calcul des Éphémérides, are published by the Bureau des Longitudes since 1796. They contain data on the calendars, the time scales and astronomical calculations. Tables, to the use of both the astronomers amateurs and the professional astronomers, give the Sun and Moon co-ordinates, the sunrise and sunset hours, the positions of planets, the satellites, the asteroids and comets as well as data on the eclipses and some other astronomical phenomena (size 15,5 x 24 cm. 384 pages) <p> <i>Since 2003, this work contains a thematic notebook. It is this year about a text on "Les multiples étoiles doubles" by F. Arenou, Observatoire de Paris. </i> <p> This work is available at the following address : <p> <table class="texte2"> <tr> <td> <p><span class="textebold">"Guide de Données Astronomiques 2008"<br>"Annuaire du BdL"<br> </span><A href="http://livres.edpsciences.org/ouvrage.php?ISBN=9782759800278" target="_BLANK" class="lien">Éditor : EDP Sciences </a><br>7 Avenue du Hoggar<br>Z.I. de Courtaboeuf<BR>B.P. 112<br>F-91944 LES ULIS Cedex A<br>384 pages<br>Prix: 29&nbsp;euros <br>ISBN : 978-2-7598-0027-8<br></p></td></tr> </table> http://www.imcce.fr/en/actualites/index.php?id=152 2007-12-06 These ephemerides are intended to the use by navigators. They are published by the Bureau des longitudes since 1889. They give the declinations and right ascensions of Venus, Mars, Jupiter and Saturne (hour per hour, to the tenth of minute). They give also the hours of risings and sets of the Sun and the Moon for latitudes ranging between 70 degrees North and 56 degrees South. Usually used by the sailors to take stock at sea, these ephemerides are compulsory for navigation of the high seas. <p> <table> <tr> <td> <p><i><span class="titre"> Éphémérides Nautiques 2008</i></span><br><span class="texte"> <br>Éditor: Edinautic <br>13 rue du Vieux-Colombier<br>F-75006 PARIS <br>Prix : 42&nbsp;euros <br>Format 16x24. 542 pages.<br>ISBN : 2-9522092-3-5 <br></p></span></td></tr></table> http://www.imcce.fr/en/actualites/index.php?id=147 2007-12-04 The date of the winter solstice is in 2007 at 6h 7min UTC on December 22 (7h 7min in winter french time). In the northern hemisphere, the winter solstice corresponds to the moment when the apparent longitude of the Sun is equal to 270 degrees. This date is that of the beginning of the winter. Our calendar (the Gregorian calendar) is built so that the seasons always start at the same time. Since the creation of the Gregorian calendar (1582) the winter solstice falls the 20, the 21, the 22 or on December 23. It in general falls the 21 or on December 22. It fell one December 23 in 1903 and will fall again on this date into 2303, 2307, 2311 and 2315. It fell one December 20 in 1664, 1668, 1672, 1676, 1680, 1684, 1688, 1692, 1696 and 1697 and will fall again on this date in 2080, 2084, 2088, 2092, 2096, 2492 and 2496. http://www.imcce.fr/en/actualites/index.php?id=148 2007-12-04 The orbit of the barycenter Earth-Moon around the Sun is in first estimate an ellipse. The distance Earth-sun is not thus constant and present a minimum (the perihelion) and a maximum (the <a href="#apoastre" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#apoastre','','scrollbars=yes,resizable=yes,width=580,height=600')" class="lien"> aphelion</a>). The Earth is going to pass a its <a href="#periastre" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#periastre','','scrollbars=yes,resizable=yes,width=580,height=600')" class="lien">perihelion</a> on January 2nd, 2008 at 23h 51min UTC. The distance Earth-sun will be then of 0.98328 AU ( astronomical units) that is 147 096 593km. This minimum value is not the same from one year to the next because the orbit of the Earth is not a perfect ellipse but an ellipse perturbed by the gravitational effects. We shall notice that the distance Earth-sun has not enough effect on the phenomenon of the seasons which is essentially due to the slope of the Earth rotation axis on its orbit. http://www.imcce.fr/en/actualites/index.php?id=149 2007-12-04 Like each year in January, the Earth on its orbit is going to meet the Quadrantids swarm. It was observed for the first time in 1825 and is supposed to have been ejected from an asteroid called 2003 EH1. This swarm will be visible on January 2008, between the 1st and 5th. The maximum of the meteor shower is awaited for January 3rd. Its radiant has as co-ordinates 15h 20m in right ascension and 49 degrees in declination, it is located in the constellation of the Herdsman. This radiant is circumpolar and thus observable all the night under our latitudes. The relative velocity of the meteors to the Earth will be about 41 km/S, and the zenithal hourly rate can reach 120 meteors/h. http://www.imcce.fr/en/actualites/index.php?id=146 2007-10-02 In accordance with a directive of the European Parliament and of the European Council on January 19, 2001 concerning the provisions related to the summer-time, the period of summer-time for year 2007 ends on the last Sunday of October at 3 a.m. in the morning. Thus, in the night from October 27, 2007, to October 28, 2007, at 3 a.m in the morning it is necessary to put the clocks back to 2 o'clock. http://www.imcce.fr/en/actualites/index.php?id=145 2007-09-21 In the northern hemisphere, the autumnal equinox corresponds to the moment when the apparent longitude of the Sun is equal to 180 degrees. Our calendar (the Gregorian calendar) is built to preserve a fixed date for the beginning of the seasons. The date of the autumnal equinox is in 2007 on September 23 at 9:50 UT (on September 23 at 11h: 50 French standard time). Since the creation of the Gregorian calendar (1582) the autumnal equinox falls on the 21st, 22nd, 23rd or 24th of September. Generally it falls on the 22nd or 23rd of September. It will fall on September 21st in 2092 and it will be the first time since the creation of the Gregorian calendar. That will reproduce in 2096, and then it will be necessary to wait the year 2464 so that it falls on September 21st again. It fell one September 24th in 1803, 1807, 1903, 1907, 1911, 1915, 1919, 1923, 1927 and 1931, and will fall again on this date in 2303 and that will be the last time. The day of the equinox, if we disregard atmospheric refraction, the duration of the night is equal to the duration of the day. It is also the day when the Sun rises due east and sets due south. The autumnal equinox in the Northern hemisphere corresponds to the spring equinox in the Southern hemisphere. http://www.imcce.fr/en/actualites/index.php?id=144 2007-07-25 During these last years many small satellites of the big planets were discovered. A recent circular of the International Astronomical Union (IAUC 8857) claims the discovery of the sixtieth Saturn satellite by the CASSINI Image Science team (Space Science Institute, Boulder, USA). This small object which would be of a diameter of approximately 1 km, was discovered on images acquired on 30 May, then found on previous CASSINI observations distributed between June 2004 and June 2007. Its orbit lies between that of the satellite S XXXII Methone and that of the satellite XXXIII Pallene. The semi major axis of its orbit is 197 700 km, its eccentricity is about 0.001, its inclination 0.1 degree and its orbital period is 1.03650 days. The provisional denomination is S/2007 S4. http://www.imcce.fr/en/actualites/index.php?id=143 2007-07-03 The orbit of the Earth-Moon barycentre around the Sun is, at first approximation, an ellipse. The Earth-Sun distance is not constant and presents a minimum <a href="#pericentre" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#pericentre','','scrollbars=yes,resizable=yes,width=580,height=600')" class="lien">(perihelion)</a> and a maximum <a href="#apocentre" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#apocentre','','scrollbars=yes,resizable=yes,width=580,height=600')" class="lien">(aphelion)</a>. The Earth will pass to its aphelion on July 6th, 2007 at 23h 52 min UTC. The Earth-Sun distance will be then of 1.01670594387ua is exactly 152 097044,24 km. This maximum value is not the same year after year because the Earth orbit is not a perfect ellipse but an ellipse perturbed by the gravitational effects. It can appear paradoxical that this maximum distance from the Sun is reached whereas we are in summer and the weather is hot in our hemisphere. This is due to the inclination of the rotation axis of the Earth with respect to the perpendicular of its orbit plan (the ecliptic). At the summer solstice (on June 21th in 2007), a date close to the passage of the Earth at aphelion, the Sun passes to the zenith of the tropic of Cancer. In Northern hemisphere the elevation of the Sun on the horizon and the duration of its illumination are then maximum. This effect contributes more to the climate than the distance to the Sun. The seasons are reversed between Northern hemisphere and Southern hemisphere. However it is false to believe that for our hemisphere, the fact that the Earth is at aphelion in summer and at perihelion in winter (towards January the 4th) would moderate the contrast of the seasons then would amplify it in southern hemisphere. It is also erroneous of saying that the day of the summer solstice is the day when the Sun culminates with its higher elevation in the Northern hemisphere! That is true only for the places located at the North of the Cancer tropic. The date of passage of the Earth in perihelion and that of passage in aphelion advance in our calendar. In this way in approximately 9.800 years, the Earth will pass in perihelion on June 21th at the time of the summer solstice. http://www.imcce.fr/en/actualites/index.php?id=141 2007-05-24 In the northern hemisphere the summer solstice corresponds to the date when the apparent longitude of the Sun is equal to 90 degrees and it marks the beginning of this season. Our calendar (the Gregorian calendar) is built so as to remain close to a fixed date for the beginning of the seasons. The date of summer solstice in 2007 is on June 21th at 18h 6m UTC. In the Gregorian calendar created in 1582, the summer solstice can occur on June 19th, 20th, 21th or 22th. It occurred on June 20th in 1896 and will fall again on this date in 2008. It occurred on June 22th in 1975 and will fall again on this date in 2203, 2207, 2211 and 2215 then in 2302. The summer solstice will fall on June 19th in 2488 and it will be the first time since the creation of Gregorian calendar. On the day of the summer solstice, for an observer located on the tropic of Cancer, the direction of the Sun points toward the zenith at twelve o'clock. Farther to the North this phenomenon never occurs. The day of solstice is the day when for a given location of the Northern hemisphere, the duration of the day is maximum. The summer solstice in the Northern hemisphere corresponds to the winter solstice in the Southern hemisphere. http://www.imcce.fr/en/actualites/index.php?id=140 2007-03-20 One reads sometimes in certain reviews that the axes of the Large Channel of the Castle of Versailles are directed East-West and North-South. Some in it is deduced, with good reason, that the Sun was to lie down in the axis of the large channel the days of the equinoxes. However the azimuth of the axis is not perfectly East-West, it deviates some from approximately 22° what changes the dates considerably where this phenomenon is observable. The altitude of the floor in front of the frontage of the castle of Versailles turned towards the Large Channel is of 142m, the horizon in the direction of the large channel elevated because of a hill of 128 meters altitude is located at 10650 meters. The azimuth of the axis of the Large Channel is of 111°49' 56 "is approximately 111°50 '; (approximately 292 ° northern). By holding account of the atmospheric refraction and these various parameters we calculated that the center of the Sun lies down in 2005 in the axis of the large channel at the following dates:<p> <table class="texte" border="1" align=center> <tr align=center><td>Sunset in the axis of the Grand Canal</td> <td>Hour of sunset (TLF)*</td><td>Azimuth</td></tr> <tr align=center><td> The 26th April 2007</td><td> 20h 54min 16s</td><td>111° 02' 39"</td></tr><tr align=center><td> The 27th April2007</td><td> 20h 55min 44s</td><td>111° 33' 02"</td></tr><tr align=center><td> The 28th April 2007</td><td> 20h 57min 11s</td><td>112° 03' 06"</td></tr> <tr align=right><td colspan=3>* TLF = French legal time</td></tr> </table> <p> <span class="textebold">Some precise details:</span><br> If the horizon were badly estimated these results can be shifted one day or two. The same if one goes up in altitude, for example, if one observes since the first stage of the castle, the results can also shift one day. It would be advisable to take photographs to check these forecasts. Moreover these calculations were made with a certain value of the horizontal atmospheric refraction, but the refraction varies with the atmospheric conditions (pressure, temperature...) the moments of sleeping can thus vary slightly compared to the predicted values. We gave these values to the second of time near but it is only the internal precision of calculation, the precision of the prediction counts held of uncertainties on the refraction is of about a minute of time.<p> If one studies the data above one notes that the azimuth of the center of the Sun to its sleeping never falls exactly into the axis from the channel, it is nearest for the median dates (on April 27 and on August 15), it is slightly in the south (towards the left) when the azimuth is lower than 111°49' 56 "and slightly in north (towards the line) when the azimuth is higher than 111°49' 56". In all the cases it is possible to take a photograph in the axis of the large channel but the center of the Sun will be more or less high compared to the horizon. One can also exploit the height of the observer while going down or while rising compared to the terrace of the frontage. If one goes up, the center of the Sun will be higher, if one goes down, the center of the Sun will be lower.<p> <span class="codered">Caution:</span> <br>If the Sun with its sleeping dazzles you, do not look at it directly, it is that it is still too high on the horizon. In this case prevent photographing it without filter, you are likely to damage your camera and your sight if you use an apparatus with aiming reflex. http://www.imcce.fr/en/actualites/index.php?id=139 2007-03-09 Researchers from IMCCE and Berkeley University have discovered a second moon orbiting the asteroid 45 Eugenia. This body was the first around which a satellite, named Petit-Prince, was observed from the ground in 1998.<p> This new result has been obtained by analyzing three images acquired in February 2004 from the 8 m VLT telescope "YEPUN" at the European Southern Observatory in Chile. This second moon is provisonaly named S/2004 (45) 1. Its size is about 6 km.<p> After the discover of the triple asteroid 87 Sylvia, 45 Eugenia is the second triple asteroid discovered between Mars and Jupiter in the Main Belt. http://www.imcce.fr/en/actualites/index.php?id=136 2007-02-26 n the Northern hemisphere, the spring equinox corresponds to the moment when apparent longitude of the Sun is equal to 0 degree (the direction of the Sun is then that of the gamma point, origin of celestial longitudes). Our calendar (the <a href="#gregorian_ca" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#gregorian_ca','','scrollbars=yes,resizable=yes,width=582,height=600')" class="lien">Gregorian calendar</a>) is built so as to preserve a fixed date for the seasons beginning. The date of spring equinox is, in 2006, <span class = "textebold">March 21th, at 0h 7min UTC (1h7min Paris standard time).</span> <P>Since creation of the Gregorian calendar (1582) the spring equinox is on March 19th, 20th or 21th. At XIXth and XXth centuries it always is on March 20th or 21th. In the past, it was on March 19th in 1652, 1656, 1660, 1664, 1668, 1672, 1676, 1680, 1684, 1685, 1688, 1689, 1692, 1693, 1696, 1697, 1780, 1784, 1788, 1792 and 1796. It will again fall on March 19th in 2044. At the equinox day, if we ignore atmospheric refraction, duration of the night is equal to the duration of the day. It is also the day when Sun rises full East and lie down full West. The spring equinox in the Northern hemisphere corresponds to the autumn equinox in the Southern hemisphere. http://www.imcce.fr/en/actualites/index.php?id=137 2007-02-26 In accordance with the decree of April 3rd, 2001 of the Ministry for the economy, Finances and of Industry, relating to the French standard time, the period from summer time for the year 2007 begins last Sunday from March to 2a.m. morning. Therefore, <span class="textebold">in the night on March 24th to 25th 2007, at 2a.m. it will be 3a.m. </span> http://www.imcce.fr/en/actualites/index.php?id=138 2007-02-26 After almost three months of weak activity, the ?shooting stars? are back. Lyrides constitute the first substantial meteoritic shower of spring and announce the return of the beautiful days. With usual activity of approximately 20 meteors per hour, and exceptionally of more than 100, it is one of the rare meteors shower associated to the comet at long period. It is about <a href= "#G1Thatcher" onClick="MM_openBrWindow('/fr/ephemerides/donnees/comets/index.php','','scrollbars=yes,resizable=yes,width=580,height=600')" class="lien"> C/Thatcher</a>, observed for the last time in 1861. Dominique François Jean Arago (1786-1853) then directing of the observatory of Paris, recognized maximum of Lyrides activity on April 22th of each year. We observe them after 21h (standard time) between the 16 and the 25. Their <a href="#radiant" onClick="MM_openBrWindow('/en/ephemerides/astronomie/glossaire.php#radiant','','scrollbars=yes,resizable=yes,width=580,height=600')" class="lien">radiant</a> is located near the circumpolaire star <B>Vega</B> of the Lyre constellation, from where them name. They are shooting stars enough fast, with a relative speed of 49 km/S. http://www.imcce.fr/en/actualites/index.php?id=133 2007-01-22 IMCCE provides annually the ephemerides «Connaissance des Temps ». These ephemerides, created in 1679 by Joachim Dalancé, are published under the responsibility of the "Bureau des longitudes" since 1795. Therefore it results from a historical long line.<br> These data are published for the use by astronomers, professors and students. This book is divided into two parts. The first part gives the current state of knowledge on the fundamental astronomical constants, scales of time, reference systems, rotation of the Earth, coordinates changing as well as explanations necessary to the calculation of the predictions. The second part gives, for the current year, the positions of the Sun, the Moon, the planets and the main satellites. Furthermore an elaborate software is provided on CDROM and gives accurate positional ephemerides, as well as the hours of rises and sunsets and the dates of the phenomena of the Galilean satellites... Starting from 2007, the ephemerides of the Sun, the planets and the Moon are issued from the highly accurate numerical model INPOP06 adjusted on the most recent observations. Format 17,5x24. 368 pages. <p> <DL> <DT> <span class="codered"><i> Editor : </i></span> <DD><a href="#" class="lien" onClick="MM_openBrWindow ('http://livres.edpsciences.org/ouvrage.php?ISBN=978-2-86883-963-3','','menubar=yes,scrollbars=yes,status=yes,location=yes,resizable=yes,width=770,height=550')"> EDP Sciences </a> <BR> 7 Avenue du Hoggar<BR> Z.I. de Courtaboeuf<BR> B.P. 112<BR> F-91944 LES ULIS Cedex A <BR> Price : 37 euros<BR> <em>ISBN : 978-2-86883-963-3</em><br> </DL>