Eyes on the Skies - Chapter 6/7: Beyond Earth
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6. Beyond Earth
The Hubble Space Telescope.
It is by far the most famous telescope in history.
And for good reason.
Hubble has revolutionised so many fields in astronomy.
By modern standards, Hubble's mirror is actually quite small.
It only measures about 2.4 metres across.
But its location is literally out of this world.
High above the blurring effects of the atmosphere, it has an exceptionally
sharp view of the Universe.
And what's more, Hubble can see ultraviolet and near-infrared light.
This light just cannot be seen by ground-based telescopes because
it is blocked by the atmosphere.
Cameras and spectrographs, some as big as a telephone booth
dissect and register the light from distant cosmic shores.
Just like any ground-based telescope, Hubble is upgraded from time to time.
Spacewalking astronauts carry out servicing missions.
Broken parts get refurbished.
And older instruments get replaced with newer and
state-of-the-art technology.
Hubble has become the powerhouse of observational astronomy.
And it has transformed our understanding of the cosmos.
With its keen eyesight, Hubble observed seasonal changes on Mars
a cometary impact on Jupiter
an edge-on view of Saturn's rings
and even the surface of tiny Pluto.
It revealed the life cycle of stars, from their very birth and baby days
in a nursery of dust-laden clouds of gas, all the way to their final farewell:
as delicate nebulae, slowly blown into space by dying stars
or as titanic supernova explosions that almost outshine their home galaxy.
Deep in the Orion Nebula, Hubble even saw the breeding ground of new
solar systems: dusty disks around newborn stars that may soon
condense into planets.
The space telescope studied thousands of individual stars in giant globular
clusters, the oldest stellar families in the Universe.
And galaxies, of course.
Never before had astronomers seen so much detail.
Majestic spirals, absorbing dust lanes, violent collisions.
Extremely long exposures of blank regions of sky even revealed
thousands of faint galaxies billions of light-years away.
Photons that were emitted when the Universe was still young.
A window into the distant past, shedding new light on the
ever-evolving cosmos.
Hubble is not the only telescope in space.
This is NASA's Spitzer Space Telescope, launched in August 2003.
In a way, it is Hubble's equivalent for the infrared.
Spitzer has a mirror that is only 85 centimetres across.
But the telescope is hiding behind a heat shield that protects
it from the Sun.
And its detectors are tucked away in a dewar filled with liquid helium.
Here the detectors are cooled down to just a few degrees
above absolute zero.
Making them very very sensitive.
Spitzer has revealed a dusty Universe.
Dark, opaque clouds of dust glow in the infrared when heated
from within.
Shock waves from galaxy collisions sweep up dust in telltale rings
and tidal features, new sites for ubiquitous star formation.
Dust is also produced in the aftermath of a star's death.
Spitzer found that planetary nebulae and supernova remnants are laden
with dust particles, the prerequisite building blocks of future planets.
At other infrared wavelengths, Spitzer can also see right through a dust
cloud, revealing the stars inside, hidden in their dark cores.
Finally, the space telescope's spectrographs have studied
the atmospheres of extrasolar planets - gas giants like Jupiter
that race around their parent stars in just a few days.
So what about X-rays and gamma rays?
Well, they are completely blocked by the Earth's atmosphere.
And so without space telescopes, astronomers would be totally blind
to these energetic forms of radiation.
X-ray and gamma ray space telescopes reveal the hot
energetic and violent Universe of galaxy clusters, black holes
supernova explosions, and galaxy collisions.
They are very hard to build, though.
Energetic radiation passes right through a conventional mirror.
X-rays can only be focused with nested mirror shells made of pure gold.
And gamma rays are studied with sophisticated pinhole cameras
or stacked scintillators that give off brief flashes of normal light
when struck by a gamma ray photon.
In the 1990s, NASA operated the Compton Gamma Ray Observatory.
At the time, it was the largest and most massive scientific
satellite ever launched.
A fully fledged physics lab in space.
In 2008, Compton was succeeded by GLAST:
the Gamma Ray Large Area Space Telescope.
It will study everything in the high-energy Universe from dark
matter to pulsars.
Meanwhile, astronomers have two X-ray telescopes in space.
NASA's Chandra X-ray Observatory and ESA's XMM-Newton Observatory
are both studying the hottest places in the Universe.
This is what the sky looks like with X-ray vision.
Extended features are clouds of gas, heated to millions of degrees by
shock waves in supernova remnants.
The bright point sources are X-ray binaries: neutron stars or
black holes that suck in matter from a companion star.
This hot, infalling gas emits X-rays.
Likewise, X-ray telescopes reveal supermassive black holes in
the cores of distant galaxies.
Matter that spirals inward gets hot enough to glow in X-rays
just before it plunges into the black hole and out of sight.
Hot but tenuous gas also fills the space between individual galaxies
in a cluster.
Sometimes, this intracluster gas is shocked and heated even more
by colliding and merging galaxy clusters.
Even more exciting are gamma ray bursts, the most energetic
events in the Universe.
These are catastrophic terminal explosions of very massive, rapidly
spinning stars.
In less than a second, they release more energy than the Sun does in
10 billion years.
Hubble, Spitzer, Chandra, XMM-Newton and GLAST
are all versatile giants.
But some space telescopes are much smaller and have much more
focused missions.
Take COROT, for example.
This French satellite is devoted to stellar seismology and the study
of extrasolar planets.
Or NASA's Swift satellite, a combined X-ray and gamma ray observatory
designed to unravel the mysteries of gamma ray bursts.
And then there's WMAP, the Wilkinson Microwave Anisotropy Probe.
In just over two years in space, it had already mapped the cosmic
background radiation to unprecedented detail.
WMAP gave cosmologists the best view yet of one of the earliest
phases of the Universe, more than 13 billion years ago.
Opening up the space frontier has been one of the most exciting
developments in the history of the telescope.
So what's next?