The Hubble Space Telescope was launched almost ten years ago - and the Universe would never look the same again...
by Nigel Henbest
December 1999, and
NASA has scrambled a space shuttle for an emergency mission. It's
a crack crew, on a flight that's been brought forward six months.
Short of a human catastrophe in space, there's only one satellite
that can command this sort of attention - the Hubble Space Telescope.
Launched almost 10
years ago, Hubble is the jewel in NASA's crown. While planetary
missions fail, and endless arguments dog the International Space
Station, Hubble has been consistently turning up trumps, with stunning
images of deep space and new insights into the birth and evolution
of the Universe.
When Sky & Telescope
magazine recently polled readers for the cosmic images of the century,
two came in miles ahead of the rest of the pack: the Apollo astronauts'
first view of the Earth from the Moon - and the Hubble Space Telescope's
glorious image of the great dark pillars in the Eagle Nebula.
View from the top
On the scientific
front, Hubble's achievements are also out-of-this-world. Its
an international mission - a collaboration between NASA and the
European Space Agency - and literally thousands of astronomers from
all over the world have used Hubbles eagle eye to dissect
over 13,000 objects in the cosmos. The data sent back to Earth would
fill over ten thousand CD-Roms.
in astronomy demonstrates the maxim that bigger isnt necessarily
better, even where telescopes are concerned. Astronomers have a
choice of some 30 ground-based telescopes that are larger than Hubble.
The space telescope's unique advantage is its crystal-clear vision.
While other telescopes must look upward through the Earth's churning
atmosphere, Hubble has an undistorted view of the cosmos.
In theory, that is.
Soon after Hubble's launch, astronomers found that Hubble's images
were blurry - due to a fault in shaping its main mirror, which threw
out its intended curve by about 1/50 the diameter of a human hair.
In December 1993, visiting astronauts installed 'contact lenses'
- in reality, small curved mirrors - which corrected the fault.
And since then, Hubble hasn't looked back.
Science from space
Jupiters black eyes, after it was assaulted
by Comet Shoemaker-Levy-9
The space telescope
has looked at every type of object in the Universe, from the nearest
- the Moon - to the most distant galaxies ever seen. It wasn't really
designed to investigate planets, but even in the Solar System Hubble
has turned up trumps. When the Mars Pathfinder mission was on its
way to the Red Planet, NASA controllers used Hubble to monitor dust
storms on the target world. The space telescope also observed a
massive storm on Saturn, and showed - for the first time - Pluto's
moon Charon clearly separate from Pluto itself. Most important,
Hubble had a prime view of Comet Shoemaker-Levy-9's smash into Jupiter
in 1994. The telescope saw both the giant fireballs as the comet
fragments impacted the planet, and the vast 'black eyes' left on
Jupiter's clouds afterwards.
In the realms of the
stars, Hubble has revealed previously unsuspected aspects of the
birth of stars and planets. In the great Orion Nebula, Hubble has
found dark dusty discs orbiting around young stars - almost certainly
on their way to condensing into systems of planets. That famous
picture of the Eagle Nebula also contains more than meets the eye.
Small specks on the side of the giant dust columns are similar discs
surrounding young stars. But here, the ultraviolet radiation from
young hot stars nearby is boiling away the dusty discs before they
have a chance to condense: these planetary systems are stillborn.
At the other end of
a star's life, Hubble has followed the fate of gases that erupted
in the most spectacular star-explosion of recent times: Supernova
1987A. Hubble has revealed rings and loops of gas around the now-defunct
star, showing that during its lifetime the star was already shedding
gas in copious quantities.
The cosmological eye
Anatomy of an exploding star: Supernova 1987A
But it's in the further
Universe that Hubble has really come into its own. The telescope
is named after American astronomer Edwin Hubble, who - in the 1920s
- proved that the entire Universe is expanding. The rate of expansion
is known as Hubble's Constant. If we can measure Hubble's Constant
accurately, we can work out the age of the Universe. This was the
prime scientific goal of eponymous space telescope.
A team of cosmologists
led by Wendy Freedman, of the Carnegie Observatories, employed the
Hubble Space Telescope to patiently track down the distances to
more and more remote galaxies. Combine these distances with the
speed these galaxies are racing away from us, and you find the Hubble
Constant. In May 1999, Friedman's 27-strong international team announced
the bottom line: the Universe is 12 billion years old.
The telescope's namesake
would have been proud of this achievement alone. But the Hubble
Space Telescope's sharp eye has revealed much on the cosmic horizon
that Edwin Hubble would never even have dreamt of.
Black holes and dark matter
Peering right into
the heart of nearby galaxies, Hubble has discovered small discs
of hot gas are spinning round at a frantic rate. The high speed
can only be explained if each disc is orbiting a massive black hole
in the galaxy's core. These observations mean that almost all galaxies
contain a central black hole.
Further out, Hubble has focused on 'gravitational
mirages' around whole clusters of galaxies. These ethereal arcs
represent the light from more distant galaxies, bent and distorted
by the gravity of the galaxy cluster. From the size and shape of
the mirages, astronomers can calculate how much mass the cluster
contains. In most cases, it's about ten times more than the total
mass of the galaxies themselves - showing that the cluster must
contain huge amounts of 'dark matter.'
Deep within galaxy M87, a supermassive black hole whirls gas
around, and ejects a narrow beam of electrons
And Hubble has played
a key role in the latest and most exciting cosmological discovery
- that the Universe is not just expanding, but accelerating. International
teams of astronomers have been tracking down exploding stars - supernovae
- in distant galaxies, using wide-angle telescopes on the ground.
When they find a likely new dim smudge of light, they turn to Hubble
to check it out. Comparing these distant supernovae with exploding
stars in nearby galaxies, the astronomers discovered they are all
dimmer than expected. According to theory, this can only happen
if the Universe is blowing itself apart faster and faster.
Cosmic mirage: distorted images of distant galaxies form a
glowing spiders web around nearby galaxy cluster Abell
2218. False-coloured to show brightness
results are all good solid science - but they are only indirect
inferences from what Hubble actually sees. Hubble's real eye-opener
has been its uncanny ability to see back into the past.
There's no special
magic about this. Because light takes a finite amount of time to
travel across space - 300,000 km every second - we see everything
in the Universe as it was in the past, at the time that its light
left it. We see the Sun as it was just over eight minutes ago; the
nearest star four years in the past; and the Andromeda Galaxy as
it was two million years ago.
But Hubble's penetrating
eye peers not just millions of years into the past, but billions
of years back in time. We're pretty sure that Andromeda hasn't changed
much in past two million years; but look at a galaxy say six billion
light years away - half the age of the Universe back in time - and
we are surely seeing it at a more adolescent phase of its existence.
In 1995, astronomers
pointed the Hubble Space Telescope at a spot of sky just above the
stars that make up familiar pattern of the Plough. There's nothing
here that our eyes can see; nothing that telescopes on Earth had
revealed as interesting. Hubble was staring at a seemingly black
spot of sky to see further than any other telescope had revealed.
And the Hubble Deep
Field came up trumps. Even the nearest galaxy here was 500 times
more remote than Andromeda. And the most distant are so far away
that we see them when the Universe was only one-tenth its present
age. The more distant galaxies don't look anything like the placid
spirals we see around us today. Most are disrupted in some way,
and many appear to comprise two or more galaxies colliding with
Our deepest view into the Universe: some galaxies here are
11 billion light years away
The Hubble 'time machine'
is thus showing us how galaxies were born. In the beginning, it
seems there were only small galaxies. As time went by, they amalgamated
into bigger galaxies, like our Milky Way.
This month's servicing
mission is the third in Hubble's history. Almost four years after
it April 1990 launch, the first repair crew famously fixed Hubble's
faulty eyesight. They also replaced one of its bulky cameras, and
changed over the solar panels. In 1997, astronauts installed a new
spectrograph for splitting up light from faint stars and galaxies
and an infrared camera.
Originally, the third
mission was planned for next June. But Hubble's gyroscopes - essentially
for pointing in the correct direction - have been suffering repeated
problems. On 13 November, the fourth of Hubble's six gyroscopes
failed, and the telescope had to be shut down.
So NASA has sent in
the cavalry - a extra mission carrying many of the most experienced
American and European astronauts. As well as replacing the gyros,
the mission involved installing a new computer and replacing the
tape recorder with a solid-state recorder.
But the other components
scheduled for next June aren't yet ready for space. They'll be taken
up on a fourth mission in spring 2001. Hubble will then boast a
new camera that will map dark matter across the cosmos; a new cooler
that will reactivate its infrared camera; and fresh solar arrays.
The final servicing
mission is scheduled for 2003. Astronauts will install a newer version
of Hubble's standard 'camera' and a spectrograph for investigating
ultraviolet light, which will show signs of gases fresh from the
'Son of Hubble'
In 2008 - astronomers
hope - Hubble will be succeeded by a bigger and better instrument,
currently known as the Next Generation Space Telescope. It will
also be cheaper: NASA is well aware that Hubble ran well over budget,
costing almost $2 billion at launch. The Next Generation Space Telescope
must come in at quarter of that amount.
Currently, four groups
are tendering for the contract. All of them are designing a main
mirror eight metres across - over three times bigger than Hubble's,
which means it can see objects ten times fainter. It's impossible
to put such a big mirror inside a rocket for launch, so it will
be made in sections which will click together once the telescope
is in space.
The new telescope
will be much flimsier than Hubble, and so much lighter in weight.
Instead of a space shuttle, it's need only a medium-class rocket
launcher. And, instead of orbiting the Earth, the Next Generation
Space Telescope will follow its own orbit around the Sun - 1.5 million
km beyond Earth's orbit. At this location, the so-called Lagrangian-2
point, our planet's gravity still ensnares the telescope, so it
travels with the Earth through space at a constant distance.
Artists impression of the Next Generation Space Telescope:
its exposed mirror is three times the size of Hubbles
Huge solar panels
provide the telescope with power, and - just as important - shield
it from the Sun's heat. With the Next Generation Space Telescope
naturally cooled down to the temperature of deep space, it can observe
faint heat signals from the farthest reaches of the Universe. It
will peer beyond where even Hubble can see, and explore an epoch
before the youngest galaxies explored by Hubble.
With this ultimate
time machine, cosmologists hope to puzzle out the last remaining
major mystery of the Cosmos - how did stars and galaxies first form.
The Next Generation Space Telescope's infrared cameras will reveal
the very first galaxies forming after the Big Bang. The early stars
in these galaxies shone in ordinary light - like the Sun - but the
expanding Universe has stretched this radiation so that it arrives
here as infrared.
Just as Hubble was
launched to measure the age of the Universe, yet became the ultimate
exploring machine in all areas of astronomy, so the Next Generation
Space Telescope will undoubtedly reveal far more than anyone can
A stately retirement?
Currently, NASA intends
to close Hubble down in 2010. But it hasn't decided what to do with
the venerable instrument then. One option is to raise it to a higher
orbit, where it will 'hibernate' indefinitely. Another is to bring
Hubble back to Earth, for a place of honour in the Air and Space
Museum in Washington.
General information about Hubble
Hubbles best pictures - the Hubble Heritage Project
Space Shuttle missions
Next Generation Space Telescope
Nigel Henbest is a staff writer. His latest books (both with Heather Couper) are Universe (Channel 4 Books) and Space Encyclopedia (Dorling Kindersley).
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