Once launched, Nasa’s Hubble successor will be the world’s
most powerful telescope with the ability to probe deeper and further back into
space than ever before.
The launch has been delayed by 14 years and is roughly ten
times over budget, although once in orbit will hopefully give scientists a more
detailed look at the start of the universe, the birth of stars, and possibly
the origins of life.
Originally set for a Christmas Eve launch on the back of an
Ariane 5 rocket, poor weather conditions at Europe’s Spaceport in French Guiana
has forced a 24-hour delay.
Encapsulation of the JWST inside the cargo bay of the rocket
was completed last Friday and it is now poised for blast-off just after midday
on Saturday.
If all goes according to plan, the $9bn instrument will be
released from the rocket after a 26-minute ride into space.
It will then take the Webb telescope a month to coast to its
destination in solar orbit roughly one million miles from Earth – about four
times the distance from the Moon.
This is much further away than where the Hubble Telescope
orbited at just 340,000 miles from the Earth.
Webb’s instruments, which make heavy use of the infrared
light spectrum, have been fine-tuned to search for potentially life-supporting
atmospheres around scores of newly documented exoplanets, or those which orbit
stars other than our own.
It will also be used to observe worlds much closer to home,
such as Mars and Saturn’s icy moon Titan.
To study these distant objects the telescope must be cooled
to within a few tens of degrees above Absolute Zero or -273°C.
This is to prevent radiation from the telescope and its
instruments swamping the astronomical signals. To achieve this Webb will have a
huge multi-layer sunshield which is the area of a tennis court.
Webb’s main telescope mirror is 6.5m diameter, the largest
ever flown in space and is gold-coated to optimise its ability to reflect
infrared light. Its 18 segments will fold up inside the rocket for launch, then
unfold in space.
Last month, astronomers used a new planet-detection
algorithm to identify 366 new exoplanets, including one planetary system that
comprises a star and at least two gas giant planets.
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