William Herschel is justly famous for finding the planet Uranus in 1781 from the garden of his house in Bath, England. But he made another important discovery for which he is less well remembered.
He placed a thermometer beyond the rainbow of colours cast by a prism, and found that the temperature suddenly rose at one point.
It showed that the spectrum continued into an invisible region, including the area he discovered, which we call the infrared.
Fittingly, a new telescope is due to be launched into space this Thursday, 14 May, named after William.
Europe’s Herschel Space Observatory is specially designed to observe the sky with an infrared eye, probing the universe in a far part of the region beyond visible light that William found.
That will allow it to peer through clouds of dust and see how stars are born and how galaxies form. It will also see how comets and the atmospheres of other planets are made up, plus it will study the dust ejected by dying stars – the raw material that will eventually form new planets like Earth.
The Herschel telecope needs to observe from space because the infrared radiation can only be seen properly outside the Earth’s obscuring atmosphere. Its instruments will be chilled to an incredibly low temperature just above absolute zero – the minimum possible in the universe and equivalent to minus 459 F, or minus 273.15 C.
The new telescope, which will be blasted into space by an Ariane 5 rocket from Kourou, French Guiana.dwarfs the famous Hubble space telescope which is being overhauled by shuttle astronauts this week. For whereas Hubble has an eye – its light-collecting mirror – 2.4 metres wide, Herschel’s mirror measures a whopping 3.5 metres across, collecting more than twice as much light.
Skymania News was privileged to be invited to see Herschel in its dust-free clean room in September 2007 as European Space Agency engineers were completing its assembly at Frederickshafen, in southern Germany.
Its heat-detecting instruments will help astronomers learn about mysterious new worlds being found in the frozen depths of the solar system far beyond Uranus – thought to be chunks of ice and rock left over from the formation of the planets.
More than 1.300 of these objects have already been found in the domain of distant Pluto which lost its own status as a proper planet in 2006.
Herschel will have a companion on its journey, lasting many weeks, to a specially stable spot in space called a Lagrangian point, about 1.5 million km from home. A second telescope, called Planck, will look 14 billion years back in time to pick up the fading glow from the Big Bang.
This cosmic microwave background will be studied in unprecedented detail, teaching astronomers about the universe’s shape and how it evolved. It could also reveal secrets of mysterious dark matter and dark energy which are thought to make up most of the universe.
Engineers at Jodrell Bank observatory, near Manchester, Cardiff University and the Rutherford Appleton Laboratory, near Oxford, designed and built crucial radio detectors to help Planck record echoes of ancient light from across the whole sky.
Dr Richard Davis of Jodrell Bank, said: “Planck will tell us about how the universe evolved from the Big Bang into the beautiful galaxy structures we see around us today.”
Other scientists from across the UK will be closely involved in analysing the streams of data sent back from both telescopes.
The combined missions cost £1.7 billion. The UK alone has invested £13 million in Herschel and £17.4 million in Planck. But scientists say the expense, after more than 20 years of planning, will be richly repaid by the wealth of new discoveries expected.
Professor Matt Griffin of Cardiff University, is Principal Investigator for a sophisticated camera aboard Herschel called SPIRE. He said: “It will offer astronomers a very powerful tool for many studies from our own solar system to the most distant galaxies.
“The results could reveal how stars like the Sun are forming in our own galaxy today, how the galaxies grew and evolved over cosmic time, and how planetary systems can develop from the dust and gas around young stars.”
UK science minister Lord Drayson said: “These space missions are outstanding feats of engineering. Herschel is the largest telescope we have ever put into space and the instruments on Planck will operate at just a tenth of a degree above absolute zero.
“This is really cool science happening at mind-blowingly low temperatures, helping to answer some of the basic questions about the history of the universe.”
Unlike Hubble, which has operated since 1990, Herschel has a life of only three to five years and will be located too far away for a servicing visit by astronauts. It carries 2,000 litres of helium gas to keep it cool, and when that runs out, the telescope will no longer function.
Update: The two telescopes were successfully lunched on May 15 and are now heading separately for their observing location in space.
Picture: ESA artist D Ducros’s impression of Herschel being ejected from its protective shell after launch.