Irish device will allow astronomers take a longer view

Astronomers should easily be able to spot planets orbiting distant stars and gauge their potential for life when a new space telescope is put into orbit in 2013.

And a little bit of Irish pride will also fly on board the new James Webb Space Telescope. The Dublin Institute for Advanced Studies is part of a European consortium that is building the telescope with the US National Aeronautics and Space Administration.

The Irish involvement relates to one of the instruments to be carried by the Webb telescope, a device called Miri, the Mid-Infrared Instrument, explains Prof Tom Ray of the Institute's School of Cosmic Physics.

Miri will give astronomers an unprecedented view of distant objects. It will be thousands of times more sensitive than ground based instruments and will be able to see distant planets and be able to confirm whether they have either water or oxygen, two potential signs of life.

"It doesn't read ordinary light it is an instrument that looks at infrared," says Ray. "Infrared is a very good way to look for planets, particularly new planets."

It will be able to block out the light from an individual star, making it easier to spot any planets that may be nearby. "It produces an effect like an eclipse. You want that so you can search for the planets circling a star," Ray explains.

Aside from the infrared telescope, Miri also has a spectrograph, a device that can split apart and read the light coming from a distant star, galaxy or even a large planet.

This reveals whether the object is moving towards or away from us and how fast, but also tells us what elements are present. This includes indicating whether there is water there or oxygen, something that suggests living plants.

The Webb telescope's amazing power is dependent on it being kept exceptionally cold. For this reason it is sent away from our "hot" planet far beyond the moon to a Lagrange point, a place where the gravity pull of earth and sun keeps the telescope apparently stationary relative to the earth.

Liquid helium will be used to keep the optical telescope and its equipment at a temperature of about 40 degrees above absolute zero, the lowest temperature achievable.

Miri is even more of a challenge, says Ray. It sits in a helium bath that keeps it at a chilly seven degrees above absolute zero.

"The European group is doing all of the optics on Miri," Ray adds. "The Institute is responsible for the filters for the optics and the beam splitters on the spectrograph."

It is hoped the Webb telescope will have an operational life of at least 10 years.