02 October 2013

Astronomers Detect Light From Universe’s Infancy

Image Caption: This artist’s impression shows how photons in the Cosmic Microwave Background are deflected by the gravitational lensing effect of massive cosmic structures as they travel across the Universe. Credit: ESA and the Planck Collaboration. 

Astronomers report that they have detected a subtle signal from the Big Bang for the first time, giving a glimpse into the first moments of the Universe.

The Cosmic Microwave Background (CMB) signal the astronomers detected was from when the universe was just 380,000 years old. The signal was found 13.8 billion years after bouncing around different areas of the Universe by galaxy clusters and dark matter.

The signal was seen as a radio wave at a temperature just a few degrees above absolute zero. Slight variations in this temperature reveal density fluctuations in the early Universe corresponding to the seeds of galaxies and stars seen today.

CMB holds plenty of other information as well that gives astronomers an even better idea of what the early Universe was like. A small fraction of the light is polarized, giving two distinct patterns known as E-modes and B-modes. E-modes were first discovered in 2002 using ground-based telescopes, but B-modes have proven much more elusive to researchers.

The polarized patterns can arise as the light twists when crossing the Universe and being deflected by galaxies and dark matter, called gravitational lensing. The patterns can also form as a result of an enormous expansion of the Universe, called inflation.

“It’s an important checkpoint that we’re able to detect this small lensing B-mode signal and it bodes well for our ability to ultimately measure an even more elusive type of B-mode created during the inflationary Big Bang,” said Duncan Hanson of McGill University, lead author of the paper published this week in Physical Review Letters.

Scientists say that during inflation, violent collisions between clumps of matter and radiation created a sea of gravitational waves. After billions of years, those waves became integrated into a primordial B-mode component of the CMB. Finding signals like this helps yield crucial information about the very early Universe.

Astronomers discovered this signal by combining data taken from the South Pole Telescope and the European Space Agency’s (ESA) Herschel Space Observatory.

“This measurement was made possible by a clever and unique combination of ground-based observations from the South Pole Telescope – which measured the light from the Big Bang – with space-based observations from Herschel, which is sensitive to the galaxies that trace the dark matter which caused the gravitational lensing,” said Joaquin Vieira of the California Institute of Technology and the University of Illinois at Urbana-Champaign, who led the Herschel survey that was used in the study.

Scientists used Herschel data to map the gravitational lensing material along the line of sight, and then searched for correlations between that pattern and the polarized light coming from the CMB.

“It is great to see this ingenious use of Herschel data in achieving the first detection of gravitational lensing B-modes in the CMB polarization,” said Göran Pilbratt, ESA’s Herschel Project Scientist. “This work displays yet another use of the treasure trove of Herschel data.”

Read more:  Dark Energy Survey will spy on supernovae to explain universal expansion


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