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Telescopes in the Atacama desert, Chile

Aerial view over the ESO observatories on Paranal and Armazones in Chile
The Atacama desert of Chile is home to several of the world's greatest telescopes. In this aerial view, the low evening Sun accentuates the mountainous topography. The nearby Cerro Paranal hosts VLT, the Very Large Telescope of ESO, the European Southern Observatory.  In the distance to the left, ELT, the Extremely Large Telescope is being erected on Cerro Armazones.  Photo by Dainis Dravins.  Click here for a high-resolution image.
Aerial view of the Paranal-Armazones area in Chile, with telescope locations marked
The location of the forthcoming telescopes of CTA, the Cherenkov Telescope Array, is marked in the valley between Paranal and Armazones.
Aerial view of the Paranal observatory in Chile
The summit of Cerro Paranal hosts the four unit telescopes of VLT, the Very Large Telescope of ESO, as well as the VLTI interferometer. Smaller telescopes are on hills to its left, while a group of technical and visitor buildings are at right. The road at top leads to the site of ELT, the Extremely Large Telescope. Photo by Dainis Dravins.  Click here for a high-resolution image.


Wolfe Creek crater (Kandimalal), Australia

Wolfe Creek meteorite crater (Kandimalal), Australia
Wolfe Creek is the second largest 'fresh' meteorite crater on Earth (i.e., so recent that actual meteorite fragments have been found). Nearly circular, with a diameter between 870 and 950 meters, it is only slightly smaller than the Barringer crater in Arizona. It is young enough (some 120,000 years) to have retained most of its original structure.  Photo by Dainis Dravins.  Click here for a high-resolution image.
Aerial view of Wolfe Creek meteorite crater and surroundings
Europeans discovered the crater only in 1947, but to Australian aborigines it has been known since time immemorial. Its name in the local Djaru language is Kandimalal, and it is twined in legends, in particular that of rainbow serpents whose sinuous paths across the desert formed two nearby creeks: the crater is where one snake emerged from the ground (see the book by Peggy Reeves Sanday: Aboriginal Paintings of the Wolfe Creek Crater: Track of the Rainbow Serpent). The location is in the remote Kimberley region in the northern part of the state of Western Australia. During the dry season the crater can be reached by 4-wheel drive vehicles from the town of Halls Creek, which is some 150 km north along the adventurous Tanami Track. Photo by Dainis Dravins.  Click here for a high-resolution image.
Detailed view onto the bottom of the Wolfe Creek meteorite crater
The bottom 150 meters of the crater have been filled in with wind-blown sand. Rainfall is retained in the whitish gypsum areas on the central crater floor, permitting sizable trees to grow. Photo by Dainis Dravins.  Click here for a high-resolution image. 



Paths of stellar motions across the sky during 200,000 years
Full-sky map showing stars in open clusters, and their paths during the next 200,000 years, computed from measurements made by the ESA space astrometry satellite Hipparcos. Well-known clusters include the Hyades and Pleiades at top right, while the one closest in space – the Ursa Major group – spreads out all over the sky. Thicker lines indicate stars closer to us: the nearest one is Sirius and the two next ones are faint red dwarfs.

Stellar paths in each cluster converge due to effects of perspective.  Stars in each cluster move through space with a common velocity, like a flock of birds.  When receding, the angle subtended by the cluster decreases.  By combining this change in relative size with distances obtained from trigonometric parallaxes, astrometric radial velocities are obtained without using any spectroscopy. (Madsen, Dravins & Lindegren, A&A  381, 446)  Click here for a high-resolution image.  


Accretion onto a black hole in a close binary system

Artist's vision of accretion of matter from a red giant star onto a black hole
What phenomena can one expect in accretion processes? An artist's vision, combining established knowledge with predicted phenomena unfolds in this painting. In a close binary system, matter is escaping from the dynamic and unstable outer atmosphere of an evolved red giant star and impinging into an accretion disk surrounding a black hole. The accretion flow is turbulent, with eddies on many different scales. A collimated jet is ejected from the center, but after some distance it becomes unstable and disintegrates after suffering a supersonic collision with the surrounding circumstellar medium. At certain distances from the center, hydrodynamic instabilities appear as various types of waves, possibly seen by a distant observer as quasi-periodic oscillations. Painting by Catrina Liljegren, Bild & Form, Lund (ESO Messenger 78, 9; © Dainis Dravins).   Click here for a high-resolution image.