Dr Créidhe O’Sullivan is analysing patterns in radiation from the early universe for clues about how it formed. Claire O’Connell found out more.
Earlier this week, on Monday to be exact, there was a big bang in the world of physics. In case you missed it, it was about the Big Bang, or shortly after it. Scientists announced they had detected traces of gravitational waves that provide evidence of the universe expanding extremely rapidly early in its development. If the finding holds up, it would prove one of Einstein’s major theories and it would help many pieces of the puzzle about the cosmos and the nature of matter to fit together.
The results, announced by scientists working on the Background Imaging of Cosmic Extragalactic Polarization or BICEP2 project, are already being heralded as a major breakthrough, though the findings still need to be confirmed and further analysed.
Catching the waves
For now though, NUI Maynooth scientist and lecturer Dr Créidhe O’Sullivan describes the results as “very exciting.” She is part of a community of physicists who are hunting for patterns in the radiation that travels across space.
We can readily see stars because our eyes can detect the visible radiation that travels across space to us, but O’Sullivan and colleagues at the department of experimental physics at NUI Maynooth are interested in a different set of wavelengths. We can’t see them with our eyes, but by using specially designed instruments and telescopes, the researchers can detect the longer wavelengths of the ‘terahertz’ band.
Why seek it out? Because radiation at that wavelength is a good place to go looking for patterns about the formation of stars and galaxies and, if you go back far enough, what unfolded immediately after the Big Bang almost 14bn years ago.
Picking up the signals
O’Sullivan has a particular interest looking at the ‘cosmic microwave background’, energy that has been spreading out through the universe since about 380,000 years after the Big Bang. She designs lenses and mirrors for telescopes that can ‘catch’ this radiation in the terahertz band, but it’s not as straightforward as designing for an optical telescope, she explains.
“Mathematically, they are tough calculations to do. For the wavelengths we work on you can’t make the same approximations that you do at optical wavelengths, but this is our expertise at NUI Maynooth, this middle ground between optical and radio wavelengths.”
Physicists in NUI Maynooth worked on designing instruments for the European Space Agency Planck and Herschel satellites, which spent several years in space. One of the main aims of Planck was to measure variations in temperature, explains O’Sullivan. “If you look at the radiation in the cosmic microwave background, there are regions where it is slightly hotter and slightly cooler than average, and they are the imprints of galaxies starting to form.”
Hints of inflation
Planck did an excellent job of mapping these variations in temperature, according to O’Sullivan, and it also picked up another interesting type of signal in this wavelength band: patterns in the polarisation of light.
Light waves can have a direction, but as you move back towards the early universe the light tends to have almost no preference in direction, it is unpolarised, she explains. But there is a small amount of polarised light, and scientists are now on the hunt to figure out those patterns.
“A tiny fraction of a second after the Big Bang, we believe the universe underwent a period of really rapid expansion called inflation, and this would explain aspects of the Big Bang,” explains O’Sullivan. “If it did happen it would leave an imprint, it would send gravitational waves through the universe that stretch and compress space, and they would leave a particular polarisation pattern behind in the microwave background.”
Planck picked up some tantalising patterns of polarisation, and now efforts are under way to find out more from ground-based telescopes, including the BICEP2 project, which made the announcement this week about finding the imprints of gravitational waves.
While it would be ideal to look for these traces from the early universe with custom-built telescopes sent out to space (like Planck was), telescopes on Earth should now help to inform how an eventual space telescope would need to operate, explains O’Sullivan.
She was not involved in BICEP2 but she is designing optics for another polarisation-hunting project called QUBIC (Q&U Bolometric Interferometer for Cosmology), and the radiation data collected by Planck from space using instruments she helped to design should also offer more insights into this week’s announcement.
“The (BICEP2) signal from the gravitational waves is a bit higher than cosmologists were expecting,” she says. “Data from ESA’s Planck satellite are currently being analysed to see if it has seen the same thing, so we could get confirmation later this year.”
O’Sullivan started her studies in experimental physics at University College Dublin and carried out research in the University of Cambridge, the NMRC (now Tyndall National Institute) and NUI Galway before moving to NUI Maynooth. There she is part of a team where everyone has their own interests but they work together to solve problems, whether they are simulating designs on a computer or testing them out in the lab.
And as this week’s events demonstrate, working in space science always offers something new to think about, and O’Sullivan relishes the challenge.
“This area of work is always throwing up problems or things you don’t understand, you feel you are always working at the forefront and nobody knows the answer, that is exciting,” she says. “And when you stop and think about what you are actually looking at – things that happened nearly 14bn years ago – that is amazing.”
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