The long view: engineering the world’s largest telescope

An enormous ground-based telescope could provide unparalleled images of our universe


in depth

eyes on the sky

Larger telescopes will sharpen up our image of space

The ambitions of astronomers for E-ELT are commensurate with the size of the telescope. As we discover more about the universe, we also discover that there are huge gaps in our knowledge: we have found new phenomena, but we have no idea what is causing them.

One of the reasons for looking harder at the universe is that we have recently discovered that the universe is not only expanding but, contrary to expectations, that expansion is accelerating. Cosmologists have postulated that some sort of ’dark energy’ is responsible for this acceleration but there is no evidence for this. There may be some clue in the rapid expansion of the universe following the Big Bang – and to look for that, you need to look far back in space and time to dim, distant objects whose light began travelling towards Earth (or, rather, the space where Earth now exists) before that inflation.

Meanwhile, the current generation of large telescopes is discovering the existence of planets around other stars – but we know very little about them. Some of these planets are gas giants so large that they can generate their own light. E-ELT’s ability to form images 100 times sharper than Hubble will allow astronomers to study the emissions from these planets and analyse their electromagnetic spectra, which will tell us what they are made of; this may allow us to study smaller, rocky exoplanets as well. It may even tell us whether these planets have atmospheres capable of supporting life.

There are also gaps in our knowledge about when stars first formed, and how nebulae condense into stars and solar systems. Current telescopes are unable to resolve galaxies relatively close to the Milky Way into individual stars; E-ELT will be able to look at stars 10s of millions of light-years away, and will also allow us to look at the faintest, lightest stars in our own galaxy, which will tell us how long they have been shining.