The Great Space Telescopes
DISCUSSION:
Hello, my name is fill in name. Today our mission takes us to space to learn about the
great space telescopes. Telescopes help us look farther than we can with just our eyes.
When they were invented, they helped people look out into the ocean to spot ships. Now
we use telescopes to gaze at the universe around us. They help us learn more about stars,
planets, and galaxies. People even use telescopes to help search for extra-terrestrial life.
Telescopes on Earth have some problems, though. When you look at the stars at night,
they seem to “twinkle.” This is because the atmosphere bends the light coming from
stars. If a telescope is above the atmosphere, it doesn’t have that problem. Telescopes in
space can help us see even farther than we can from Earth. NASA built observatories
that are in space to see even farther than the best telescopes on Earth. These
observatories have telescopes and special detectors so scientists can examine the
radiation from planets, stars, galaxies, and other objects in space. Using the
observatories, scientists can learn what chemicals make up an object, its temperature and
motion.
Because it takes a long time for light from distant objects to reach the observatories,
scientists are actually looking at the star or planet the way it looked billions of years ago
– they are looking back in time! NASA built four Great Observatories to help scientists
better understand the universe. They are the Hubble Space Telescope (HST), The
Chandra X-Ray Observatory (Chandra), the Compton Gamma Ray Observatory (GRO),
and the Space InfraRed Telescope Facility (SIRTF).
Hubble Space Telescope
Hubble Space Telescope (HST) was launched in 1990. It was
the first Great Observatory to be launched, and it is the only one
that can be serviced. Astronauts can go into space and capture
HST and fix broken parts or upgrade older components. This
allows NASA to keep improving HST and keep making it better
and better. There have been four servicing missions to HST so
far, and a fifth one is planned for 2004. After the first servicing mission to correct a
problem with the mirror, HST has been providing wonderful images of stars, planets, and
galaxies. HST has four science instruments on board. Each instrument does a different
job and tells scientists different things about the object at which it is looking. The
instruments are all replaceable, so astronauts can take out old instruments and replace
them with even more advanced cameras and detectors. None of the original instruments
are on-board HST now.
All of the science instruments on HST have helped scientists change the way we think
about the universe. It is helping scientists determine how old the universe is, and
improving our understanding of how stars are created and die. It is also giving us a better
idea of how many galaxies there are in the universe, and how many stars have planet
systems.
Compton Gamma Ray Observatory
The Compton Gamma Ray Observatory (CGRO) was
launched in 1991 to detect gamma rays from objects
throughout the universe. At the time, CGRO was the heaviest
thing that the space shuttle had ever carried. After almost 10
years of work, CGRO’s mission ended in 2000. Before that,
CGRO was the first satellite to look for all of the natural
sources of gamma rays in the universe. Gamma Rays have
very small wavelengths and they cannot get through the
atmosphere to be detected on Earth. That is why the CGRO was so important – the only
way for scientists to detect Gamma Rays is to go into space.
The CGRO detected gamma rays from huge objects in space that give off a very large
amount of energy. CGRO investigated how galaxies are formed. It was also used to
study things like black holes, gamma bursts, and quasars. CGRO had the four largest
gamma ray detectors ever built. Gamma Ray detectors detect gamma rays when the
gamma ray interacts with the matter in the detector to create a flash of light. The brighter
the light, the more energy the gamma ray had.
Chandra X-Ray Telescope
Chandra was launched in 1999 to study objects using X-Ray
wavelengths. X-Rays come from very hot objects full of energy.
Like gamma rays, X-Rays can not get through Earth’s atmosphere,
so the only way to observe them is from space. The Chandra X-Ray
telescope is 20 times more powerful than older X-Ray telescopes. Chandra can see so
well that it can read the letters on a stop sign from 12 miles away! Chandra is designed
to study black holes, supernovae, and to look for dark matter. It will also observe
exploding stars and investigate galaxy clusters. Chandra is still a new telescope, but it
has already made some amazing discoveries. The picture below shows the black hole at
the center of the Milky Way galaxy (our home) that Chandra discovered.
Space InfraRed Telescope Facility
The Space InfraRed Telescope Facility is still being built, and is
scheduled to be launched in 2003. SIRTF will detect infrared
radiation from stars and galaxies. It is important to observe objects
using infrared wavelength because visible light can be blocked out
by things like dust. Infrared light can get through the dust so we can
see the objects behind dust clouds. Hot objects, like our sun, give
off visible light. Cooler objects – like planets and asteroids – give
off mainly infrared light. We need telescopes like SIRTF to see
them. SIRTF will study things like brown dwarfs, super planets, and
galaxies. It will also be able to look back in time to the early universe to help scientists
understand how the universe was created.
Activities
1. Now that you understand why observatories in space are useful, do you think that
they will eventually replace ground based observatories entirely? Why or why
not? Discuss your thoughts with your group.
2. Do some research and find out what observatories are being designed and
developed for the future? How will they be similar to the four Great
Observatories? How will they be different?
3. Each of the three launched observatories was named after a famous scientist or
astronomer. Do some research and learn about the people after whom Hubble,
Compton, and Chandra Observatories were named.
4. Using the attached document, make a model of the Hubble Space Telescope. It
might help to use construction paper. There are models for Chandra X-Ray
Telescope and Compton Gamma Ray Observatory at NASA’s website if you
would like to make models of those, also.