Universe shines twice as bright (Forwarded)
- From: Andrew Yee <ayee@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 16 May 2008 01:57:04 GMT
Press Office
University of St Andrews
St Andrews, Scotland
Contact:
Fiona Armstrong, Press Officer
01334 462530 / 462529
Julia Maddock
STFC Press Office
+44 1793 442094 / +44 7901 514 975
Thursday 15 May 2008
Universe shines twice as bright
The Universe is actually twice as bright than was previously thought,
according to research conducted by an international team of astronomers.
Dr Simon Driver from the University of St Andrews has discovered dust is
obscuring approximately half of the light that the Universe is generating.
Lead author Dr Driver of the School of Physics and Astronomy said, "For
nearly two decades we've argued about whether the light that we see from
distant galaxies tells the whole story or not. It doesn't; in fact only
half the energy produced by stars actually reaches our telescopes
directly, the rest is blocked by dust grains."
While astronomers have known for some time that the Universe contains
small grains of dust, they had not realised the extent to which this is
restricting the amount of light that we can see. The dust absorbs
starlight and re-emits it, making it glow. They knew that existing models
were flawed, because the energy output from glowing dust appeared to be
greater than the total energy produced by the stars.
Dr Driver explained, "You can't get more energy out than you put in so we
knew something was very wrong. Even so, the scale of the dust problem has
come as a shock -- it appears galaxies are generating twice as much
starlight as previously thought!"
The team combined an innovative new model of the dust distribution in
galaxies developed by Dr Cristina Popescu of the University of Central
Lancashire and Prof Richard Tuffs of the Max Plank Institute for Nuclear
Physics, with data from the Millennium Galaxy Catalogue, a
state-of-the-art high resolution catalogue of 10,000 galaxies assembled by
Driver and his team.
Using the new model, the astronomers could calculate precisely the
fraction of starlight blocked by the dust. The key test that the new
model passed was whether the energy of the absorbed starlight equated to
that detected from the glowing dust.
"The equation balanced perfectly," said Dr Cristina Popescu, "and for the
first time we have a total understanding of the energy output of the
Universe over a monumental wavelength range. With the new calibrated
model in hand we can now calculate precisely the fraction of starlight
blocked by the dust."
The Universe is currently generating energy, via nuclear fusion in the
cores of stars, at a whopping rate of 5 quadrillion Watts per cubic light
year -- about 300 times the average energy consumption of the Earth's
population.
"For over 70 years an accurate description of how galaxies, the locations
where matter is churned into energy, form and evolve has eluded us.
Balancing the cosmic energy budget is an important step forward," said Dr
Driver.
After carefully measuring the brightness of thousands of disc-shaped
galaxies with different orientations, the astronomers matched their
observations to computer models of dusty galaxies. From this they were
able to calibrate the models and, for the first time, determine how much
light is obscured when a galaxy has a face-on orientation. This then
allowed them to determine the absolute fraction of light that escapes in
each direction from a galaxy.
Dr Driver explained the discovery that only half of the visible starlight
gets out, while a mere 10 percent of the UV radiation escapes from
galaxies. He said, "When the dust blocks the light, it is effectively
heated and glows like the thermal images seen with military night vision
goggles.
"When we look at galaxies using infrared satellites, we actually see the
warm dust glowing. The amount of energy which the Universe is releasing at
these wavelengths exactly balanced our determination of how much UV and
visible light is absorbed by the dust."
While modern instruments allow astronomers to see further into space, they
can't eliminate the obscuring effect from these tiny dust grains. The
work is set to continue but with a change of focus from the study of the
Universe as a whole, to the study of individual galaxies. This requires
two new facilities which are coming online this year. The first is the
VISTA telescope, which will soon commence operations in Chile and the
second is the Herschel satellite due for launch later in the year.
Dr Driver continued, "We still aren't able to observe the Universe in its
full glory, however we do now better understand the effect that all of
this dust is having on scientific observations."
UK astronomers enjoy full access to both of these facilities through the
UK's membership, paid by the Science and Technology Facilities Council, of
the European Southern Observatory and the European Space Agency which are
responsible for operating these facilities.
The research is published in the latest Astrophysical Journal Letters
(10th May).
Note to Editors:
Authors: Simon Driver (University of St Andrews, Scotland), Cristina
Popescu (University of Central Lancashire, England), Richard Tuffs
(Max-Planck Institute fur Nuclear Physics, Germany), Alister Graham
(Swinburne University of Technology, Australia), Jochen Liske (European
Southern Observatory, Germany), Ivan Baldry (Liverpool John Moores
University, England).
This research has been funded by the Science and Technology Facilities
Council (STFC), the Australian Research Council, the Max-Planck Society
and a Livesey award from the University of Central Lancashire.
The Millennium Galaxy Catalogue consists of data from the Anglo-Australian
Telescope, The Australian National University's 2.3 m telescope at Siding
Spring Observatory, the Isaac Newton Telescope and the Telescopio
Nazionale Galileo at the Spanish Observatorio del Roque de Los Muchachos,
La Palma, of the Instituto de Astrofisica de Canarias, and also from the
Gemini and ESO New Technology Telescopes in Chile.
The researchers are available for interview:
Dr Simon Driver
University of St Andrew
01334-461680/ 07919305906
Dr Cristina Popescu
University of Central Lancashire
01772 893 551
Dr Ivan Baldry
Liverpool John Moores University
ikb @ astro.livjm.ac.uk
Dr Richard Tuffs
Max Plank Institute for Nuclear Physics
Richard.Tuffs @ mpi-hd.mpg.de
Dr Alister Graham
Swinburne University of Technology
Tel: +61 3 9214 8784
Dr Jochen Liske
ESO
Tel: +49 89 32006582
Note to Picture Editors:
High resolution images showing galaxies known to contain dust obscuring
the stars are available from
http://astronomy.swin.edu.au/~agraham/dust/dust.html
.
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