Hubble Floats Free
Explanation:
Why put observatories in space? Most telescopes
are on the ground. On the ground, you can deploy a heavier telescope
and upgrade it more easily. The trouble is that
Earth-bound telescopes
must look through the
Earth's atmosphere.
First, the
Earth's atmosphere
blocks out a broad range of the
electromagnetic spectrum, allowing
a narrow band of visible light to reach the surface.
Telescopes which explore the Universe using light
beyond the visible spectrum, such as those onboard the
Compton Observatory
(
gamma rays),
the
ASCA satellite
(
x-rays),
or the new
ultraviolet and
infrared instruments on the
above-pictured
Hubble Space Telescope
(HST), need to be carried above the absorbing atmosphere.
Second, the
Earth's atmosphere blurs the light
it lets through. The blurring is caused by varying density and
continual motion of air. By orbiting above the Earth's atmosphere,
the Hubble can get clearer images.
In fact, even though
HST
has a mirror 15 times smaller than
large Earth-bound telescopes,
it can still resolve detail almost 100 times finer.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
