Heavens' kitchen: from primordial soup to cosmic pancakes
The spectacular ‘Fireworks galaxy’ (NGC 6946) as observed by the GMOS instrument on the 8 meter Gemini North telescope. Credit: Gemini Observatory/Travis Rector, University of Alaska Anchorages
Ms Ana Babic, Mr Justin Bronder, Professor Roger Davies, Dr Matthew Jarvis
Dark energy and dark matter make up 95% of our Universe yet this 'dark sector' remains a complete mystery. 'Everyone has looked at the night sky and wondered what is out there,' says Roberto Trotta of the University of Oxford. 'It's no different for scientists, we are only just beginning to understand.'
By observing supernovae explosions of stars at the end of their life scientists have discovered that the rate of expansion of the Universe is accelerating. Supernovae, although short lived, are extremely bright and have the useful property of always having almost the same luminosity, so their observed brightness from earth can be used to calculate their distance. These 'standard candles' provided evidence that the speed at which galaxies are moving away from each other is in fact increasing. 'If gravity were the only force acting upon objects in the Universe the expansion should be slowing down,' explains Roberto. 'There is some other force out there, what we call dark energy.' The existence of dark matter was first suggested after visible objects in the Universe were observed to be behaving in unexpected ways.
Earlier this year Steve Rawlings, Roberto and colleagues at the University of Oxford launched 'The Dark Sector Initiative', a unique collaboration between theorists, observers and statisticians to explain the fundamental nature of the dark sector. The team are also key players in the development of the Square Kilometre Array (SKA) Radio Telescope that will be by far the largest radio telescope ever built. Light from the most distant of the billion galaxies that SKA is predicted to detect will have taken ten billion years to reach earth, more than two-thirds of the age of the Universe. By mapping out the galaxy distribution back to this early time, SKA will help to explain the nature of dark energy.
The dark sector is also being probed by examination of the Cosmic Microwave Background Radiation (CMBR). First identified in 1965, the CMBR provided clear evidence for Big Bang theory. 'The CMBR provides a kind of cosmic Rosetta stone whose inscriptions tell us about the ingredients of the Universe, including dark matter and dark energy,' explains Roberto. Data from the Cosmic Background Imager, a microwave telescope in Chile, provides the Oxford team with images of the distribution of 'seeds' of galaxies just 400,000 years after the Big Bang. Roberto and his colleagues are also hopeful that Clover, an exciting new experiment studying the CMBR, may detect gravitational waves from the Big Bang and provide evidence in favour of the theory of inflation, which describes what happened in the very first instants of the life of the Universe.
Powerful telescopes and increased computing power are enabling scientists to identify the cosmic ingredients of the Universe. 'Solving the mysteries of dark energy and dark matter will lead to a new fundamental understanding of how the Universe works and what it contains,' says Roberto. 'This will have unimaginable consequences for our knowledge'.