April 8-May 17, 2009 -- Picture shows the gigantic telescope of ESA’s space-based infrared observatory, Herschel, the largest mirror ever flown in space. Herschel will have an unprecedented view of the cold universe, bridging the gap in the spectrum between what can be observed from ground and earlier space missions of this kind. The telescope is named after the British astronomer William Herschel who discovered infrared radiation while studying the Sun.
When the Herschel and Planck observatories part company shortly after lifting off together on board an Ariane 5 rocket from the European Spaceport in French Guiana, both missions will coldly go where none has gone before, seeking clues to the origins of the universe and its stars and planets in the coldest, oldest depths of space.
Their destination is some 1.5 million kilometres from Earth -- about four times the distance to the Moon -- and it will be several months before both are in position and operating.
They are aiming for the vicinity of L2, one of five “Lagrange points” in our solar system, named after an 18th century French mathematician who calculated that for any two astronomical bodies linked by gravity there were five points at which their combined pull would hold a smaller body in place. Three of these points lie on a line running through the Sun and the Earth; one of these, L2, is on the “dark side” of the Earth, shielded from the Sun and offering an uninterrupted view of the universe.
The twin European Space Agency missions, collecting data for hundreds of astronomers from dozens of countries, have epic goals.
Planck, ESA’s “time machine”, is Europe’s first mission to study Cosmic Microwave Background -- the “relic radiation” still echoing around space from the Big Bang creation of the universe, some 14 million years ago -- and will do so to a degree of sensitivity never achieved before.
CMB, the “first light” of the universe, is everywhere; it cannot be detected visually, but only by measuring its temperature -- at minus 270 degrees Centigrade, very close to absolute zero on the Kelvin scale. Planck’s job is to spot the minute variations in this temperature which, says ESA, are “nothing less than the imprints left in the CMB by the primeval ‘seeds’ of today’s huge concentrations of matter”, such as galaxies.
By mapping these, Planck could show which of the competing theories about the birth and evolution of the universe are correct. It might also reveal the age of the universe, discover whether it will go on expanding for ever or is doomed to collapse and prove the existence of the “dark matter” thought to comprise 90 percent of it.
Herschel’s telescope, the biggest sent into space, will feed three instruments designed to study parts of the electromagnetic spectrum -- from the far infrared to sub-millimetre -- almost impossible to monitor from Earth because they are absorbed by water vapour in the atmosphere.
It is at these long, invisible wavelengths that vast, cold tracts of the universe radiate, including stars and planets in the early stages of life and hidden from astronomers by the clouds of gas and dust from which they are being created. Seeing “through” this screen, Herschel’s instruments could discover how galaxies and stars form and evolve.
Parked in the shadow of the Earth, Herschel will be free from the interference of the planet’s infrared radiation and spared the wild swings of temperature caused by sunrise and sunset that would play havoc with its thermally sensitive instruments.
Because they are searching for clues in the coldest parts of space, the instruments on both observatories must be operated at similarly low temperatures; to achieve this Herschel will carry 2,000 litres of liquid helium. When the coolant runs out, the missions are over -- Herschel has an expected operating life of three years, Planck of only 15 months. (Story: Simon Morgan)