When the Herschel
Space Observatory reaches its orbital perch, it will be set to boldly look
where no telescope has looked before.
Herschel
will be launched
this week by the European Space Agency (ESA), in tandem with the Planck
telescope, and its arrival marks a new chapter in infrared astronomy.
Infrared
light is better known to most of us as heat. But heat isn't emitted just by the
hottest objects — even an ice cube gives off infrared energy.
Celestial
objects with surface temperatures of about 3600 degrees Fahrenheit (2,000
Celsius) — cold compared to the Sun which has a surface temperature of about 9900
F (5,500 C) — actually radiate most of their energy at infrared wavelengths.
Aging stars, planets and dust are all objects in the universe best observed in
the infrared, appearing as dark blobs in the visible spectrum, but until
Herschel, infrared observations of these objects have been incomplete.
Clean
view
For one
thing, ground-based telescopes are not as effective at these observations
because infrared light is largely blocked by water in Earth's atmosphere. Other
space-based missions have only looked in particular infrared wavelengths.
Herschel will offer a more comprehensive look from the clear
window of space.
"Instead of
looking out through a dirty window, you're going to get a clean view,' said Paul
Goldsmith, the NASA project scientist for Herschel at the Jet Propulsion
Laboratory in Pasadena, Calif., which provided some of the key technology for
the telescopes..
With its
11.5-foot (3.5-meter) mirror (the largest ever sent into space and almost 1.5
times larger than the Hubble Space Telescope), Herschel will be able to explore
more in the far-infrared than any other mission, both within and outside our
own galaxy. Herschel will collect almost 20 times more light than any previous
infrared space telescope.
The
telescope (named for the astronomer William Herschel who discovered infrared
light 200 years ago) will detect light from objects as cold as minus -440
degrees F (-263 C).
With the
telescope, astronomers will be able "to really get a good view of the universe
in the far-infrared," Goldsmith said.
New
infrared views
Within our
solar system, Herschel will examine asteroids, Kuiper belt objects and comets,
which are fossils of the early solar system that could hold clues to the raw
ingredients that formed the planets, including Earth. One ingredient of
particular interest is water.
"One of the
most interesting targets for Herschel is the same water that blocks our view of
the universe," Goldsmith told SPACE.com.
Some
astronomers think that comets, which are sometimes thought of as "icy
snowballs," could have supplied the Earth's water. As comets near the sun in
their orbit, their ice melts into water — Herschel can detect the water's
signature, Goldsmith explained.
Herschel
will also look for signs of water in interstellar clouds and compare it to the
water signatures in our own solar system, to "see how we're connected,"
Goldsmith said.
Astronomers
will also be looking for another molecule familiar to us earthlings — oxygen.
It is predicted to be abundant in the interstellar medium, but so far no
instrument has definitively detected it.
In the
Milky Way, Herschel will study star-forming regions to get a first glimpse at
the stages of early star formation and some of the galaxy's youngest stars.
Baby stars are enshrouded in wombs of cold gas and dust.
"You just
can't see what's going on inside until the star is actually born," Goldsmith
explained. But Herschel should be able to see through the clouds to see the
infant stars beyond.
"We'll get
some quite beautiful images, we think, of star-forming regions," Goldsmith
said.
Signs of
planets
Astronomers
also hope to use Herschel to peer into the dusty debris discs that encircle
stars, where planets are thought to be formed.
Herschel will
also investigate star formation outside our own galaxy. Astronomers know that
star and galaxy formation got started fairly quickly after the Big Bang and
that star formation was much more intense in the
younger universe. The young galaxies that churned out stars then would have
shone brightly in the infrared, making Herschel an ideal telescope to observe
them and better understand the stellar baby boom in the early universe and how
it might have differed from star formation today.
"We hope to
unravel that a little bit," Goldsmith said.
The
galaxies are thought to make up a diffuse infrared cosmic background. The
Spitzer Space Telescope can just barely resolve these galaxies, but Herschel,
with its sharper focus, should be able to "nail down" the source of the
background, Goldsmith said.
Once
Herschel reaches its final destination at the L2 Lagrangian
point of the sun-Earth system — a gravitational stability point in space
about 1 million miles (1.5 million kilometers) from Earth in the opposite
direction of the sun — it needs a couple months to get up and running. But once
it is, it will have 3.5 years to get the "first really in-depth
looks" at the hidden infrared folds of the universe, Goldsmith said.
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