Hubble captures extraordinary view of Universe
29 September Daily Mail
The Hubble Space Telescope (HST) has produced one of its most
extraordinary views of the Universe to date.Called the eXtreme Deep
Field, the picture captures a mass of galaxies stretching back almost to
the time when the first stars began to shine. But this was no simple
point and snap - some of the objects in this image are too distant and
too faint for that.
Rather, this view required Hubble to stare at a tiny patch of sky for
more than 500 hours to detect all the light."It's a really spectacular
image," said Dr Michele Trenti, a science team member from the
University of Cambridge, UK."We stared at this patch of sky for about 22
days, and have obtained a very deep view of the distant Universe, and
therefore we see how galaxies were looking in its infancy."
The XDF will become a tool for astronomy. The objects embedded in it
can be followed up by other telescopes. It should keep scientists busy
for years, enabling them to study the full history of galaxy formation
and evolution.The new vista is actually an updating of a previous HST
product - the Hubble Ultra Deep Field.That was built from data acquired
in 2003 and 2004, and saw the telescope burrow into a small area of
space in the Constellation Fornax (The Furnace). Again, it necessitated
many repeat observations, and revealed thousands of galaxies, both near
and far, making it the deepest image of the cosmos ever taken at that
time.
But XDF goes further; it dials down into an even smaller fraction of
the UDF.
It incorporates more than 2,000 separate exposures over 10 years
using Hubble's two main cameras - the Advanced Camera for Surveys,
installed by astronauts in 2002, and the Wide Field Camera 3, which was
added to the observatory during its final servicing in 2009.To see what
it does, Hubble has to reach beyond the visible into the infrared. It is
only at longer wavelengths of light that some of the most distant
objects become detectable.
"Modelling studies suggest that galaxies start small with fewer
features and then as they grow in size they acquire the magnificent look
that we can see in the closest galaxies observed in this XDF image,"
explained Dr Trenti.Of the more than 5,000 galaxies in the XDF, one of
them (UDFj-39546284) is a candidate for the most distant galaxy yet
discovered. If this is confirmed, it means it is being seen just 460
million years after the Universe's birth in the Big Bang. Scientists
time that event to be 13.7 billion years ago.
Until that corroboration, another of the image objects,
UDFy-38135539, probably holds the record. We see this galaxy as it was
600 million years after the Big Bang.
But as remarkable as the XDF is, it is a prelude for an even deeper
Hubble view that is likely to be released later this year. A team led
from Caltech (US) and Edinburgh University (UK) has acquired more than
100 hours of additional observations, doubling the exposure time in the
all-important near infrared wavebands made possible by WFC3.
The expectation is that it will contain galaxies even closer to the
Big Bang.
To see the first starlight in the Universe will most likely require
Hubble's successor.
The James Webb Space Telescope, which is scheduled to launch in 2018,
will carry a much larger mirror and even more sensitive instruments.
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