Artist's impression of the E-ELT in Chile's Atacama Desert.
Artist's impression of the E-ELT in Chile's Atacama Desert.
Yann Verdo

PARIS – To infinity ... and beyond!

Within the next decade, if all goes according to plan, we Earthlings will have two crucial instruments at our disposal to probe the outer reaches of the universe. Doing so, will allow us to go back in time to the very birth of the universe, 13.7 billion years ago or so, since seeing far is tantamount to seeing early: the light emitted by a galaxy ten billion light-years away from Earth shows us, by definition, this galaxy as it was ten billion years ago ...

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Yes, we know: Mind-blowing.

The first of these two instruments is a giant eye, 39-meters in diameter, supposed to be built by 2020 on a mountaintop in Cerro Armazones, Chile. The construction of the European Extremely Large Telescope (E-ELT), the next-generation telescope of the European Southern Observatory (ESO), will not begin until 90% of the funding has been pledged by the member states – which is not the case yet. But a milestone has just been reached with the project receiving the support of three new countries – including France – last month at the ESO council.

The second instrument, also scheduled to be up and running in 2020, is not an optical telescope like the E-ELT – but a radio telescope. The Square Kilometer Array (SKA), composed of a myriad of parabolic and dipole antennas scattered through Southern Africa and Australia, can be described a giant pair of ears listening to the radio waves emitted by the distant universe.

The projects’ estimated costs: 1 billion euros for the E-ELT; 1.5 billion euros for the SKA.

Astronomers from all kinds of disciplinary fields – planetology, astrophysics, cosmology, etc. – expect a lot from these two Earth-based telescopes which will work in parallel with the future James Webb Space Telescope (JWST) that NASA will put in orbit in 2018. "Apart from solar physics, the E-ELT will be able to tackle almost all the key questions of astronomy," says Denis Mourard, deputy director of the National Institute of Sciences of the Universe of the French National Centre for Scientific Research (CNRS).

Twenty times more sensitive than the Very Large Telescope – its predecessor at the ESO – the E-ELT will be an invaluably powerful tool in the detection of new extra-solar planets. Almost all of the 850 or so exoplanets that have been discovered to date were found indirectly – by methods that allowed their existence to be guessed, not seen. Only the most massive exoplanets, several times the mass of Jupiter, have allowed themselves to be scrutinized, orbiting very-hard-to-see dying stars known as "brown dwarfs."

In this regard, the E-ELT’s high-resolution power is nothing short of a revolution. It will provide us with images of exoplanets that are very similar to the Earth, and reside in their parent star’s so-called habitable zone, i.e. at a distance where the temperature allows the existence of liquid water. More importantly, the E-ELT will allow us to perform a spectroscopy of these planets – and therefore analyze the composition of their atmospheres, in the hope of detecting the signs of a possible extraterrestrial life such as water, carbon dioxide or ozone. "The Grail," as Jean-Gabriel Cuby, the director of the Laboratory of Astrophysics of Marseilles, puts it.

Shedding light on "The Dark Ages"

Another "Grail" – this time within the range of both the SKA and the E-ELT – would be to finally lift the veil on the birth of the universe. Most of its first billion-years of existence remain elusive. This infantile period is called "The Dark Ages", an age during which the first stars were formed in vast gaseous clouds of hydrogen and helium – the two essential elements that emerged from the Big Bang. The SKA is particularly well equipped to study these opaque clouds – the 21-centimeter line radiation from primordial hydrogen cannot be seen by optical telescopes but is within the spectrum that radio telescopes can detect.

This does not mean that the E-ELT will not have its say. The images of the distant universe that it will provide will help us to have a more accurate idea of the value of some of the most fundamental "cosmological constants," the parameters that have been having a profound impact on the physical properties of the universe for the past 13.7 billion years. Like the way it swells in all directions like a rubber balloon, with each celestial body running away from the other. We have known since 1998 that this rapid cosmic expansion (inflation), far from slowing down over the billions of years, is accelerating under the influence of a mysterious repulsive force called the "dark energy," although it is unclear at what rate.

In order to find this out, cosmologists will point the E-ELT at a distant galaxy and measure the speed with which it moves away from the Earth. Repeating the same action 20 years later on the same galaxy, they should be able to deduce, by subtraction, how much the cosmic expansion has accelerated in the meantime. The answer will not be known until 2040 at best. Going back in time requires patience.

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