How the next space telescopes will unveil the dark ages of the Universe
5 April 2000For current astronomers, the 'darkest' epoch of the universe is the time when the first galaxies started to form and evolve: no instrument today can peer into that era. Unveiling it will be the task of the next giant space-and ground-based telescopes, which will provide different pieces of information to complete the jigsaw at last. As astronomers explained last week in Munich at the conference 'Astronomical Telescopes and Instruments 2000', ESA's space telescope FIRST will take the lead in this task, unveiling the galactic collisions that produced the first stellar 'baby boom' in the history of the Universe. NGST, a mission currently under study by several spaces agencies, will follow two years later.
Astronomers today have more tools to study the origin of the Universe than the origin of the galaxies, even though the first event obviously happened long before. The reason is twofold: firstly, the epoch when the first galaxies formed was most likely already dusty and current telescopes get confused by the dust; secondly, today's instruments are simply not sensitive enough - in the meantime, cosmologists can use other techniques to study the Big Bang. The epoch of galaxy formation has therefore so far remained a true 'dark age'. However, a brief and unproven chronological report of the events at that time could be the following. Sometime after the Big Bang the first stars formed, possibly in small clusters; with time they started to merge and grow, and the mere accumulation of matter triggered the formation of more stars; these stars produced dust, which in turn was 'recycled' to make more stars. By then the first galaxies would already be in place, and they would also merge to form larger systems. These galactic collisions triggered an intense formation of stars in the Universe.
This is where ESA's Far Infrared and Submillimetre Telescope, FIRST, comes into play. FIRST, that merited a full-day session at the conference of the International Society for Optical and Engineering in Munich, will be launched in 2007 to see the emission from dust illuminated by the first stellar 'baby booms' in the history of the Universe. With FIRST data astronomers will already know how the first galaxies behaved.
"FIRST will open a new generation of giant space telescopes, and will be the first instrument able to look very far in space and time without being confused by the dust",explained ESA astronomer Gvran Pilbratt, FIRST project scientist. "FIRST will actually be able to observe light re-emitted by the dust, which is illuminated by the intense star-formation, and hence can be used to measure the total amount of energy produced by the new-born stars. This will help us to understand how some primeval galaxies formed".
FIRST will be located approximately 1.5 million kilometres away from Earth and will have a 3.5 metre telescope, the largest ever sent to space - and 'a real technological challenge', engineers said in Munich. FIRST's instruments - two cameras and a high-resolution spectrometer - represent a jump ahead in the technology behind infrared astronomy: FIRST will have well over a thousand of detectors, while its predecessors had less than ten.
Clearing the view for NGST
By seeing the dust enshrouding some primeval galaxies FIRST's data will complement results from the project next in the list: NGST, the 'Next Generation Space Telescope'. NGST, also highlighted as a leading mission at the conference in Germany, is a near-infrared observatory under study by NASA, ESA and the Canadian Space Agency (CSA) that could become the successor for the Hubble Space Telescope in 2009. It will have an even larger mirror, 8 metres in diameter, and will be very efficient at seeing the very first galaxies directly.
But the dust produced by the first generations of stars will still hamper NGST's view, which means that it will see only a fraction of the light from some dusty primeval galaxies. To estimate how much remains unseen, astronomers will need to know how much dust is covering the picture.
"NGST will see much sharper than FIRST. It will be very powerful at detecting the radiation coming from very distant galaxies, but it will not be able to say how much starlight the dust is hiding. We need both observatories to complete the jigsaw", Pilbratt says.
FIRST: Goran Pilbratt gpilbratastro.estec.esa.nl Tel: +31-71-5653621
NGST: Peter Jakobsen pjakobseastro.estec.esa.nl Tel: +31-71-5653614