Documents & Ressources - Résultat de la recherche
Résultats de la recherche
Halley's Comet
image
Légende : Halley’s Comet, is a well-known periodic comet, named after the English astronomer Edmond Halley. It has an orbital period of approximately 75 years and is visible from Earth with the naked eye when it passes through the inner solar system.
The image shows Halley’s Comet, officially designated 1P/Halley, with a tail of gas and dust streaming away from the Sun. It was taken from the La-Silla-Observatory in Chile in 1986 during Halley's Comet's last visit to the inner solar system. The stars in this image appear elongated or as lines of three different colored dots as image was created from three separate observations in different colors of light and the telescope was tracking the comet, which was moving very slightly compared to the background stars. Note that the comets tail does not point in exactly the same direction as the elongation of the stars. This shows us that the comet tail is not always behind the comet, but instead pointing away from the Sun.
The comet passes its perihelion (closest distance to the Sun) at a distance of around 0.59 astronomical units, right between the orbits of Mercury and Venus. Beyond Neptune, it reaches its aphelion (furthest distance from the Sun) at a distance of approximately 35 astronomical units. Halley's Comet reached aphelion in December 2023 and is now moving inwards again. It is expected to be seen with the naked eye from Earth again in mid-2061.
Crédit : ESO
Lien du crédit
Termes du glossaire:
Aphélie , Comète , Queue cométaire , La comète de Halley , Périhélie
Licence : Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Icônes
Fichier
( image
5.23 MB)
Hello Comet, shall we dance?, by Robert Barsa, Slovakia
image
Créé pour l'OAE
Légende : Third place in the 2021 IAU OAE Astrophotography Contest, category Comets.
This beautiful and poetic image taken from Slovakia in July 2020 captures the comet C/2020 F3 (Neowise). The direction of the tails of the comet provides a clue as to the position of the Sun. In the past, the appearance of a comet in the skies could be accompanied by apprehension and even fear from those who did not know what these objects really are. Through careful observations and the applications of knowledge from physics, chemistry and geology, we now understand that comets are objects left over from the earliest days when the Solar System formed. The most distinctive features of a comet are the bluish ion (gas) tail, and whitish dust tail, which can extend for tens of millions of kilometres. These distinctive features, easily observable with the unaided eye together with an understanding of the science, are no longer cause for fear, rather they help us understand the history of our Solar System, and bring awe, joy and contemplation, as portrayed in this image.
Crédit : Robert Barsa/IAU OAE
Termes du glossaire:
Comète , Queue cométaire
Catégories :
Astronomie à l'œil nu
, Système solaire
Licence : Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Icônes
Ce fichier est sur Zenodo ( image 2.59 MB)
Comet C/2020F3 (Neowise) with separate dust and ion gas tails and a green glowing coma, by Dietmar Gutermuth, Germany
image
Créé pour l'OAE
Légende : Second place in the 2021 IAU OAE Astrophotography Contest, category Comets.
Comets have a very interesting structure comprising of four main parts: the nucleus, composed of rock, dust and frozen gases, typically spanning a few kilometres, although bigger ones have been observed; a small atmosphere of gas surrounding the nucleus (only present when the comet approaches its closest point to the Sun), called coma; and the two distinctive cometary tails (there is at times third tail). The green colour of the coma is due to carbon and nitrogen present in the coma reacting with the Sun’s ultraviolet radiation. The tail that we are mostly used to observing – dust tail and is composed of micron sized dust particles, the second tail composed of charged particles – ion or gas tail. The tails are released only when the comet approaches the Sun at a distance where the heat and radiation emanating from our star is intense enough to vaporize the frozen gases. The dust tail is curved, while the gas tail is straight and always points away from the Sun as this is carried by the solar wind - flow of charged particles emitted by the Sun. As comets are formed by leftover material, they carry with them important information about the early stages of the Solar System’s formation. This beautiful image shows the comet C/2020 F3 (Neowise), as seen from Germany in July 2020, with three of the four structures clearly visible – coma, gas, and dust tail.
Crédit : Dietmar Gutermuth/IAU OAE
Termes du glossaire:
La chevelure (ou coma) de comète , Comète , Queue cométaire
Catégories :
Système solaire
Licence : Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Creative Commons (CC) Attribution 4.0 International (CC BY 4.0) Icônes
Ce fichier est sur Zenodo ( image 683.77 kB)
Comète Hale-Bopp
image
Légende : Image de la comète C/1995 O1 (Hale-Bopp), prise le 4 avril 1997, avec un temps d'exposition de 10 minutes. Le champ représenté est d'environ 6,5°x6,5°. Deux queues s'étendent à partir de la chevelure brillante : une queue de poussière blanche-jaunâtre, orientée à l'opposé du déplacement de la comète et une queue de gaz bleuâtre, orientée à l'opposé du Soleil.
Crédit : E. Kolmhofer, H. Raab ; Observatoire Johannes Kepler, Linz, Autriche
Lien du crédit
Termes du glossaire:
Comète , Queue cométaire
Catégories :
Système solaire
Licence : Creative Commons (CC) Attribution - Partage dans les Mêmes Conditions 3.0 non transposé Creative Commons (CC) Attribution - Partage dans les Mêmes Conditions 3.0 non transposé Icônes
Fichier
( image
882.93 kB)
La comète 67P/Tchourioumov-Guérassimenko
image
Légende : Le noyau de la comète 67P/Tchourioumov-Guérassimenko (ou 67P/Чурюмова — Герасименко en Russe) est une "boule de neige sale" composée d'un mélange de glaces et de poussières. Il a la forme de deux grands lobes : l'un de 4,1 km × 3,3 km × 1,8 km, l'autre de 2,6 km × 2,3 km × 1,8 km. Ces lobes sont reliés par un petit pont. Lorsqu'un noyau cométaire tel que celui-ci s'approche du Soleil, sa matière gelée et glacée est chauffée et se transforme en gaz. Ce gaz, combiné à la poussière qui s'y trouve, constitue la matière de la coma et de la queue, qui sont caractéristiques de la comète.
Crédit : ESA/Rosetta/NAVCAM
Lien du crédit
Termes du glossaire:
Comète , Noyau de la comète
Catégories :
Système solaire
Licence : Creative Commons (CC) Attribution - Partage dans les Mêmes Conditions 3.0 Organisations Internationales Creative Commons (CC) Attribution - Partage dans les Mêmes Conditions 3.0 Organisations Internationales Icônes
Fichier
( image
4.75 MB)
