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TOPIC: Distant Galaxies


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Astronomers 'spot' unseen galaxies

Planet Earth sits in the middle of the vast emptiness of space, according to the human eye.
But a new discovery by European astronomers has confirmed that it is not so empty after all.

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Older galaxies more peculiar, census shows

The most common type of galaxy changed from a "peculiar" shape six billion years ago to a typical spiral shape today, and may indicate galaxies have a more violent past than previously believed.
A team of European astronomers took a 'snapshot' of galaxies today and in the past using the Hubble Space Telescope and the Sloan Digital Sky Survey, and compared the two.

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Un télescope naturel révèle un tout petit berceau d'étoiles dans l'Univers primitif

Une équipe d'astronomes dirigée par Jean-Paul Kneib et Kirsten Kraiberg Knudsen, a identifié une galaxie poussiéreuse, véritable nurserie d'étoiles alors que l'Univers avait seulement 1,5 milliards d'années. Parmi les galaxies primordiales produisant massivement de nouvelles étoiles c'est la galaxie la plus lointaine et la plus petite connue à ce jour.
Cette galaxie a été découverte grâce au phénomène de lentille gravitationnelle, aussi appelé télescope cosmique. D'après la théorie de la relativité générale, un amas de galaxies, du fait de sa forte masse, déforme l'Espace-Temps. Ainsi, la lumière d'une galaxie lointaine, alignée avec cet amas de galaxies, est amplifiée comme si on la regardait à travers un télescope. Avec l'aide de ce télescope cosmique, les astronomes ont pu mettre en évidence, pour la première fois, l'existence d'une petite galaxie primordiale très poussiéreuse, alors que l'Univers n'avait que 1,5 milliards d'années, se situant derrière l'amas de galaxies Abell 2218.

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Hubble telescope detects oldest galaxies

The refurbished Hubble space telescope has set a new distance record by discovering the oldest galaxies ever seen, dating back 13 billion years, or 600 to 800 million years after the Big Bang, NASA said Tuesday.
The never-seen-before galaxies are key to interpreting the development of the first stars and the formation of the first galaxies that later evolved into the elliptical galaxies like our own Milky Way that now populate the universe, the space agency said.

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A University of British Columbia astronomer has produced the most detailed images of deep space from 12 billion years ago, using data from the European Space Agency's Herschel Space Observatory.
Recently presented at the first International Herschel Science Meeting in Madrid, Spain, the images by UBC post-doctoral fellow Gaelen Marsden reveal tens of thousands of newly-discovered galaxies at the early stages of formation - just one billion years after the Big Bang, when the Universe was a thriving nursery of newly-formed stars.

"These images allow us to see 10 times more galaxies than ever before and with stunning clarity. It is incredibly rewarding to see the high sensitivity and resolution that the new Herschel data have enabled. They allow us to take a close look at the stars during early and vital stages of formation, and could change the way we study formation in the future" - Gaelen Marsden.

Source: University of British Columbia



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An international team of astronomers has used the Hubble Space Telescope to take the deepest image of the universe ever, revealing the farthest and youngest known galaxies. The results, which could offer insights into how the first galaxies formed and evolved after the Big Bang, are being presented Jan. 5 at the American Astronomical Society meeting in Washington, D.C.
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The Hubble Space Telescope has captured a snapshot of when the universe was just a toddler, 600 million years after the Big Bang, the earliest image yet.
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The NASA/ESA Hubble Space Telescope has broken the distance limit for galaxies and uncovered a primordial population of compact and ultra-blue galaxies that have never been seen before. The data from the Hubble's new infrared camera, the Wide Field Camera 3 (WFC3), on the Ultra Deep Field (taken in August 2009) have been analysed by five international teams of astronomers. Some of these early results are being presented by various team members on 6 January 2010, at the 215th meeting of the American Astronomical Society in Washington DC, USA.
The deeper Hubble looks into space, the farther back in time it looks, because light takes billions of years to cross the observable Universe. This makes Hubble a powerful "time machine" that allows astronomers to see galaxies as they were 13 billion years ago, just 600 million to 800 million years after the Big Bang.

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z~10 Galaxy Candidates
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Title: Constraints on the First Galaxies: z~10 Galaxy Candidates from HST WFC3/IR
Authors: R.J. Bouwens (UC Santa Cruz), G.D. Illingworth (UC Santa Cruz), I. Labbe (Carnegie Observatories), P.A. Oesch (ETH Zurich), M. Carollo (ETH Zurich), M. Trenti (U Colorado), P.G. van Dokkum (Yale), M. Franx (Leiden), M. Stiavelli (STScI), V. Gonzalez (UC Santa Cruz), D. Magee (UC Santa Cruz)
(Version v2)

The first galaxies likely formed a few hundred million years after the Big Bang. Until recently, it has not been possible to detect galaxies earlier than ~750 million years after the Big Bang. The new HST WFC3/IR camera changed this when the deepest-ever, near-IR image of the universe was obtained with the HUDF09 program. Here we use this image to identify three redshift z~10 galaxy candidates in the heart of the reionisation epoch when the universe was just 500 million years old. These would be the highest redshift galaxies yet detected, higher than the recent detection of a GRB at z~8.2. The HUDF09 data previously revealed galaxies at z~7 and z~8. Galaxy stellar population models predict substantial star formation at z>9-10. Verification by direct observation of the existence of galaxies at z~10 is the next step. Our conservative search and extensive testing for contamination and spurious images suggests that we can set reliable constraints based upon our 3 z~10 candidates, unlike a recent claim of 20 z~10 sources which appear to be spurious. The detection of galaxies at z>8 is further enhanced by our detailed analysis of 2 other faint sources likely at z~8.4 and z~8.7. Our z~10 sample suggests that the luminosity function and star formation rate density evolution found at lower redshifts continues to z~10, and pushes back the timescale for early galaxy buildup to z>10, increasing the likely role of galaxies in providing the UV flux needed to reionise the universe. The true nature of these galaxies, at just 4% of the age of the universe, will remain hidden until JWST is launched.

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NASA's Hubble Space Telescope has made the deepest image of the universe ever taken in near-infrared light. The faintest and reddest objects in the image are galaxies that formed 600 million years after the Big Bang. No galaxies have been seen before at such early times. The new deep view, taken in late August 2009, also provides insights into how galaxies grew in their formative years early in the universe's history. The image was taken in the same region as the Hubble Ultra Deep Field (HUDF), which was taken in 2004 and is the deepest visible-light image of the universe. Hubble's newly installed Wide Field Camera 3 (WFC3) collects light from near-infrared wavelengths and therefore looks even deeper into the universe, because the light from very distant galaxies is stretched out of the ultraviolet and visible regions of the spectrum into near-infrared wavelengths by the expansion of the universe.

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hs-2009-31-a-web.jpg
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Position(2000): RA 03h 32m 38s.5, Dec  -27° 47' 00''.0


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