Engineering: A golden age in European astronomy

 

Europe is playing a key role in astronomy’s golden age with breakthroughs in telescopes and instruments making it possible to observe distant events in the early life of the universe.

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There is now great optimism that one of the fundamental questions of cosmology, the origin of galaxies, will be resolved within the next decade or sooner.

But the technology involved is still expensive, as instruments have to be highly sensitive and some of the observation needs to take place from space beyond the interference of the earth’s atmosphere, so an international effort is involved.

Europe's role in this global programme has been enhanced by three new instruments, including the €1 billion Herchel Space Observatory (HSO), and the European Science Foundation (ESF) has been helping to coordinate the effort by bringing many of the principle users of these facilities together at an international conference.

Delegates included leading specialists in all aspects of galaxy and star formation.

Galaxies are formed when areas of dust and gas collapse under gravity, forming clumps within which densities become sufficient to trigger the nuclear fusion required for star formation.

This phenomenon has been obscured from optical telescopes by clouds of dust that absorb visible light.

However, the dust re-emits this visible light absorbed from galaxies at longer wavelengths, and the latest telescopes are now able to detect this at sufficient sensitivity to unravel the processes being observed.

Eelco van Kampen, chair of the ESF Research Conference 'The Origin of Galaxies: Exploring Galaxy Evolution with the New Generation of Infrared-Millimeter Facilities', explained: "The main reason for a new golden age is the sheer number of new instruments that will become available over the next few years, literally opening up the universe in the far-infrared to millimetre wavelengths."

Examining a broader spectrum of wavelengths

It is not just that galaxy formation can now be observed indirectly via the radiation emitted from the dust that obscures a direct view; the new telescopes are also able to span a much broader spectrum of wavelengths.

This is crucial for understanding what is happening, because many processes, and also individual chemical elements, only reveal themselves via the radiation they emit across multiple wavelengths, rather than their intensity at a particular point of the spectrum, or single 'colour'.

"The main gain is that the whole 'spectral energy distribution' (SED) can be mapped for each source, which means that one does not only measure total luminosity, but also 'colours' and emission from specific molecules," said Van Kampen.

"From the SED one can derive many properties of the sources, including temperatures and composition."

Although there is great confidence that dramatic progress will be made, there is uncertainty over the exact nature of the discoveries to come, creating eager anticipation among astronomers.

"There will be many surprises, as this is still a relatively uncharted wavelength range," said Van Kampen.

"It is hard to predict whether surprises will be on the same scale as those in gamma-rays, where many short-lived bursts appeared quite unexpectedly, but there is great potential for the unexpected."

Very short-lived gamma-ray bursts are caused by the most powerful explosions known, and provided evidence of black holes – objects whose gravity is so intense that even light does not travel fast enough to escape.

For European researchers, there is an additional challenge – all the observations from the crucial HSO telescope have to be made within about three years before the equipment runs out of its vital helium cooling fluid, which cannot practically be replenished.

The telescope has to be kept cool to avoid emitting infrared radiation from its own fabric, which would swamp the faint signals from distant dust clouds.

"The Herschel Space Telescope has to be cooled significantly to reduce background noise, and for this purpose will be housed in a superfluid helium cryostat," said Van Kampen.

"The need for cooling means that the telescope lifetime is limited by its helium supply. We are promised at least three years of routine operations, but this could be somewhat longer if we are lucky."

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