14 February 2006
Theme 4 - How did the Universe originate and what is it made of?
Since antiquity, the Earth's inhabitants have observed the sky with curiosity and perspicacity, taking advantage of technological progress to help understand what the Universe is made of. Our present knowledge is the result of centuries of continuous cross-fertilisation between astronomical observations and theoretical constructions.
Successive steps have taken mankind closer and closer to comprehending the complexity, origin and evolution of the Universe: by recognising that we live in a planetary system and that the Earth is orbiting the Sun; by establishing that the Sun is embedded in a spiral galaxy, far from its centre; by demonstrating that the Universe is expanding and later discovering that this expansion is accelerating; and realising from dynamic evidence that most of the matter in the Universe is in an unknown form, called dark matter.
| Astronomers have found strong evidence that the Universe underwent a period of very strongly accelerated expansion a splitsecond after the Big Bang, known as inflation. But probably the biggest surprise to astronomers in the past decade has been the discovery that the current Universe has entered another period of acceleration, albeit at a much slower pace. The gravitational effect that would normally attract galaxies to each other is being overwhelmed by an apparent repulsion driving galaxies apart faster and faster. |
- Investigate the nature and origin of the Dark Energy that is accelerating the expansion of the Universe
- Investigate the physical processes that led to a phase of drastic expansion in the early Universe
- Directly detect gravitational waves from the first moments of the Big Bang (This means operating in a new frequency window: 0.1-1.0 Hz)
- Gravitational lensing by cosmic large-scale structures, and the luminosity-redshift relation of distant supernovae are the clues to the nature of the Dark Energy
- Gravitational waves from the Big Bang should leave imprints of inflation in polarisation of the cosmic microwave background
- Wide-field optical-infrared imager
- All-sky mapper for polarisation of cosmic microwave background
- Gravitational wave cosmic surveyor
| Tracing cosmic history back to the time when the first luminous sources ignited, thus ending the dark ages of the Universe, has just begun. At that epoch the intergalactic medium was reionised, while large-scale structures increased in complexity, leading to galaxies and their supermassive black holes. |
- Find the very first gravitationally-bound structures that were assembled in the Universe – precursors to today's galaxies, groups and clusters of galaxies – and trace the subsequent co-evolution of galaxies and super-massive black holes
- Resolve the far-infrared background into discrete sources, and the star-formation activity hidden by dust absorption
- Large-aperture X-ray observatory
- Far-infrared observatory
| Nature offers astrophysicists the possibility of observing objects under much more extreme conditions, in terms of gravity, density and temperature, than anything feasible on Earth. On the one hand, black holes and neutron stars are unique laboratories where the laws of physics can be probed under these extreme conditions. On the other hand, the same objects were the driving engines of the birth and evolution of galaxies, of the creation of heavy elements such as iron, and more generally, of the transformation of the primordial hydrogen and helium from which stars and galaxies were first being formed. |
- Trace the formation and evolution of the super-massive black holes at galactic centres – in relation to galaxy and star formation – and trace the life cycles of chemical elements through cosmic history
- Examine the accretion process of matter falling into black holes by the spectral and time variability of X-rays and gamma-rays, and look for clues to the processes at work in gamma-ray bursts
- Understand in detail the history of supernovae in our Galaxy and in the Local Group of galaxies
- Large-aperture X-ray observatory
- Gamma-ray imaging observatory