New Deep Images of the Universe: 200,000 Galaxies Revealed –From Hubble to VISTA

 
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Seen in in the Hubble deep background above are ubiquitous bright blue sources, presumably extremely hot ultraviolet before redshifting, 1 to a dozen or so pixels, as single or short lines of spots, and a few irregular tiny blobs, probably, as predicted in many recent simulations, the earliest massive, short-lived hypernovae, GRBs with jets at various angles to our line of sight, expanding bubbles, earliest molecular and dust clouds with light echoes and bursts of star formation, and first small dwarf galaxies, always associated with a subtle darker 3D random fractal mesh of filaments of H and He atomic gases.


Now, a new deep field view has been released by ESO's VISTA telescope, which has been trained on the same patch of sky repeatedly to slowly accumulate the very dim light of the most distant galaxies. In total more than six thousand separate exposures with a total effective exposure time of 55 hours, taken through five different coloured filters, have been combined to create this picture. 

The image below from the UltraVISTA survey is the deepest infrared view of the sky of its size ever taken. Astronomers use the word deep to mean images taken with very long total exposures that can detect the faintest possible objects. Normally many shorter exposures are taken and later digitally combined.

The VISTA telescope at ESO's Paranal Observatory in Chile is the world's largest survey telescope and the most powerful infrared survey telescope in existence. Since it started work in 2009  most of its observing time has been devoted to public surveys, some covering large parts of the southern skies and some more focused on small areas. 

The UltraVISTA survey has been devoted to the COSMOS field, an apparently almost empty patch of sky which has already been extensively studied using other telescopes, including the NASA/ESA Hubble Space Telescope. UltraVISTA is the deepest of the six VISTA surveys by far and reveals the faintest objects.

Data from the VISTA surveys — totalling more than 6 terabytes of images — are now being processed in data centres in the United Kingdom, and in the case of UltraVISTA in France, and are flowing back into the ESO science archive and being made available to astronomers around the world.

At first glance the UltraVISTA image looks unremarkable, a few bright stars and a sprinkling of fainter ones. But in fact almost all of those fainter objects are not stars in the Milky Way, but very remote galaxies, each containing billions of stars. Enlarging the image to fill the screen, and zooming in reveals more and more of them, and the image records more than 200 000 galaxies in total.

The expansion of the Universe shifts light from distant objects towards longer wavelengths. For starlight coming from the most distant galaxies that we can observe, this means that most of the light falls in the infrared part of the spectrum when it gets to Earth.

As a highly sensitive infrared telescope with a wide field of view, VISTA is uniquely powerful for spotting distant galaxies in the early Universe. By studying galaxies in redshifted light at successively larger distances, astronomers can also trace how galaxies were built up and evolved over the history of the cosmos.

Close inspection of the picture reveals tens of thousands of previously unknown reddish objects scattered between the more numerous cream-coloured galaxies. These are mostly very remote galaxies seen when the Universe was only a small fraction of its present age. Early studies of the UltraVISTA images, in combination with images from other telescopes, have revealed the presence of many galaxies that are seen when the Universe was less than a billion years old and a few are seen at even earlier times.

Although the current UltraVISTA image is already the deepest infrared image of its size in existence observations are continuing. The final result, a few years from now, will be significantly deeper still.

 

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The Daily Galaxy via ES0

Image credit: Hubble Deep Field with thanks to http://www.flickr.com/photos/rmforall/3103426063/ and www.spacetelescope.org

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