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Comet C/2020F3 (Neowise) with separate dust and ion gas tails and a green glowing coma, by Dietmar Gutermuth, Germany
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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)
Dust Clouds and Nebulae near R Coronae Australis
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Légende : The image shows a dark and dusty cloud and some bright reflection nebulae near the binary star R Coronae Australis. The dark cloud spans several light-years and is located in the constellation Corona Australis near the constellation Sagittarius, in the direction of the Milky Way's center. The cloud appears to swallow the light of distant stars behind it as the dust particles in it scatter light passing through in all directions. This gives it the appearance of a void in the sky. This dark nebula is part of the broader Corona Australis Molecular Clouds. R Coronae Australis forms part of the Coronet Cluster, a collection of young stars which formed at some point in the last two million years.
Around R Coronae Australis in the center of the image is the small reflection nebula NGC 6729 with two blueish reflection nebulae NGC 6726 and NGC 6727 lying to the upper right of it. In these nebulae the dust scatters light from bright stars near the nebula towards an observer on Earth, making it glow in this image.
Crédit : ESO
Lien du crédit
Termes du glossaire:
Nébuleuse sombre , Poussière , Nébuleuse , Milieu interstellaire , L'extinction interstellaire , Nuage moléculaire
Catégories :
Voie lactée et milieu interstellaire
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
20.18 MB)
The Pleiades M45 with Majestic Dust
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Créé pour l'OAE
Légende : Honourable mention in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.
Taken in Dar Eid in Saint Catherine/Sinai, Egypt, in October 2021, this image shows the Pleiades, an open cluster also known as The Seven Sisters.
The Pleiades are located in the north-western part of the constellation Taurus, the Bull. This constellation originates from ancient Babylonian or even Sumerian belief, where it was designated the Bull of Heaven, a mighty creature owned by the sky god. In Late Babylonian times, the Pleiades were called The Bristle at the hunchback of The Bull. In China, the asterism is also called The Hair, but this does not necessarily imply any relationship between the East Asian and West Asian names of this asterism, although exchange is hypothesised with the establishment of the Silk Road.
In ancient Babylonian texts the term The Hair does not appear. Instead, the Pleiades are only called The Star Cluster in Sumerian, and the Sumerian term was used in later languages as a loanword. The Sumerian and early Babylonian religion associated all constellations with specific deities, including gods, demons, messengers of gods. The Star Cluster was associated with a deity of the Netherworld that was called The Seven and was considered an ensemble of seven speaking weapons or strongly armed gods. The later Greek name of the Seven Sisters might possibly have sprung from an intercultural misunderstanding of this older religious association, since, in fact, seven stars are not seen in this cluster.
The star cluster of the Pleiades is really prominent in the sky, and thus was used for several cultural purposes, such as determining the calendar and the spring equinox. However, its significance is frequently overstated in cultural astronomy. As the tradition of representing it with seven dots originates from an ancient Sumerian belief, we should be careful about interpreting any group of seven dots on cave walls and archaeological sites across Europe, Asia and America from the Stone Age onwards as a representation of the Pleiades.
Modern astrophysics has found that the star cluster of the Pleiades is extraordinarily young, so there was certainly not an additional star in ancient times. Furthermore, we know that the bright stars are only the core region of an open star cluster that consists of hundreds of stars scattered over an area of the sky which exceeds the bright core by one or two of its diameters in any direction. The photograph does not even show the whole cluster. The group is thought to be about 400 light-years away from Earth, which is relatively close in astronomical terms.
Crédit : Mohamed Usama/IAU OAE
Termes du glossaire:
Amas , Objet Messier , Nuage de poussière , Nuage de gaz , Milieu interstellaire , Amas ouvert , Pléiades
Catégories :
Voie lactée et milieu interstellaire
, Astronomie à l'œil nu
, Étoiles
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 5.83 MB)
Herschel’s view of new stars and molecular clouds
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Légende : This image shows the Westerhout 3, 4 and 5 star formation regions. This area has huge amounts of gas and dust. This gas and dust hides the physical processes going on in this region from studies using visible light. This image was taken in infrared light by the Herschel Space Observatory. This infrared light allowed Herschel to see deep into these star forming regions.
In Westerhout 3, 4 and 5, huge, cold clouds of molecular hydrogen have collapsed into dense knots and filaments. Within these new structures the gas is dense and cold enough for it to collapse and form stars. These new stars give off powerful winds of charged particles, like stronger versions of the solar wind our sun gives off. These winds have combined to blow massive bubbles in the surrounding gas and dust. These are visible as the large darker voids in the image.
Crédit : ESA/Herschel/NASA/JPL-Caltech; acknowledgement: R. Hurt (JPL-Caltech)
Lien du crédit
Termes du glossaire:
Astronomie infrarouge , Formation des étoiles , Milieu interstellaire , Nuage moléculaire , Vent stellaire
Catégories :
Voie lactée et milieu interstellaire
, Étoiles
Licence : Creative Commons (CC) Attribution 3.0 Organisations Internationales Creative Commons (CC) Attribution 3.0 Organisations Internationales Icônes
Fichier
( image
4.53 MB)
The Lenticular Galaxy NGC 2787
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Légende : The lenticular galaxy NGC 2787. This galaxy is a disk galaxy but lacks the large, dominant spiral arm structure seen in the disks of spiral galaxies. Its core is very bright compared to the core of a spiral galaxy. Thin rings of dust can be seen in the galaxy's disk.
Crédit : NASA/ESA and The Hubble Heritage Team
Lien du crédit
Termes du glossaire:
Galaxie à disque , Galaxie , Galaxie lenticulaire
Catégories :
Galaxies
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
1.91 MB)
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