Transcript 24.2 – Tools for Studying Space - Earth Science

24.2 – Tools
for Studying
Space
Do Now
How does a refracting
telescope differ from a
reflecting telescope?
Do Now
How does a refracting
telescope differ from a
reflecting telescope?
Glass vs. mirror; refracting
= chromatic aberration and
reflecting = much clearer.
Key Words
Distort
Optical
Spectacular
Vocab Words
Refracting Telescope
Reflecting Telescope
Chromatic Aberration
Radio Telescope
Studying Space
Optical Telescopes
Refracting Telescopes
Reflecting Telescopes
Detecting Invisible Radiation
Radio Telescopes
Space Telescopes
Hubble Space Telescope
Special Purpose Telescope
Refracting Telescopes
 Galileo was the creator
and first user of this
type of telescope.
 His version was able
to magnify objects 30
times.
 Uses a glass lens to
bend or refract light.
Refracting Telescopes
 The most important lens in a refracting
telescope, the objective lens, produces an
image by bending light from a distant object so
that the light converges at an area called the
focus, or central point.
Refracting Telescopes
 If a telescope is used to examine an image directly, we then use a
second lens, called an eyepiece.
 The eyepiece magnifies the object that the objective lens shows.
The eyepiece shows details not shown by just the objective lens.
 Refracting telescopes were used greatly with early astronomy but it
had one major flaw, an optical defect, called chromatic aberration.
 When the image is weakened and there is a halo of color around
it.
 When blue light is in focus, a reddish halo appears.
 When red light is in focus, a bluish halo appears.
 This cannot be eliminated completely, but can be greatly
reduced by using a second lens made of a different type of
glass.
Reflecting Telescopes
 Newton was bothered by chromatic
aberration so he built telescopes that
reflected light from a shiny surface – a mirror.
 Because reflected light is not dispersed into
its component colors, the chromatic
aberration is avoided.
 Reflecting telescopes use a concave mirror
that focuses the light in front of a mirror,
rather than behind it, like a lens.
 The mirror is generally made of glass that is
finely ground and coated with a highly
reflective material, usually an aluminum
compound.
Reflecting Telescopes
There are major advantages to using a
reflecting telescope.
One disadvantage is that the secondary
mirror blocks some of the light entering the
telescope.
Optical Telescopes
 Both refracting and reflecting telescopes have
three properties that aid astronomers in their work:
 Light-gathering power
 Telescopes ability to intercept more light from
distance objects, thereby producing brighter
images.
 Resolving power
 Sharper images and finer details
 Magnifying power
 Ability to make an object larger.
Invisible Radiation

There are many things out in space that can
not be seen with an optical telescope and so
we need other types of telescopes to see
those waves.
 These telescopes extend the limits of our
vision.
 These telescopes are called radio
telescopes. They detect mostly radio waves
out in space.
 A radio telescope focuses the incoming
radio waves on an antenna, which absorbs
and transmits these waves to an amplifier,
just like a radio antenna.
Invisible Radiation
 Radio telescopes have poor resolution, making it difficult to
pinpoint a source, so that is why there are always pairs or
groups of telescopes to reduce this problem.
 Have revealed spectacular events like the collision of two
galaxies, also quasars and pulsars.
 There are some advantages to radio telescopes over optical
telescopes such as:
 Being able to view 24 hours a day
 Not affected by the atmosphere
 No protection dome needed, like an observatory
 Can see through things optical telescopes can’t
 Interstellar gas clouds
Space Telescopes
Space telescopes orbit
above Earth’s
atmosphere and thus
produces clearer images
than Earth-based
telescopes.
These telescopes are not
affected or distorted due
to Earth’s atmosphere.
Hubble Space Telescope
 The first space telescope, built by NASA, was the Hubble Space
Telescope.
 It was first put into orbit in April 1990.
 This telescope has 10 billion times more light-gathering power
than the human eye.
 It has been able to provide us with more information on our
solar system, other planets that orbit other stars, the birth of
stars, black holes, the age of the universe, and the expansion of
the universe.
 Hubble and many Earth-based telescopes have detected more
than 140 extrasolar planets.
 http://www.nasa.gov/mission_pages/hubble/main/index.html
Special Purpose Telescopes
 We have built a lot of telescopes that are used for a
specific and special purpose other than the Hubble.
 To study X-rays we use the Chandra X-Ray
Observatory
 To study infrared we use the James Webb Space
Telescope
 Voyager is used to go beyond the furthest points we
have traveled to.
 With more advances in technology the more we attempt
to understand about space.
 http://www.nasa.gov/missions/current/index.html
Group Challenge Question
Why would the moon
make a good
observatory?