Transcript 3.1 Using Technology

3.1
Using Technology
Crab Nebula (Image from HST)
3.2
Using Technology to See Beyond
the Visible
Gamma imaging of Earth
Optical Telescopes
• 1608 Dutch optician Hans Lippershey
makes one of first telescopes.
• Galileo is first person credited for using it
to look at stars.
• Optical telescopes simply gather
and focus light from distant stars
so we can see it.
• BUT Optical telescopes are only
useful for viewing objects that
emit light.
• Stars and galaxies emit more than just
visible light.
• They also emit radio waves, infrared (heat)
waves, and x-rays..
• These are all forms of electromagnetic
energy.
• All forms of EMR travel at the speed of
light (300 000 Km/s) but have different
wavelengths and frequencies.
• Wavelength: The measurement from one point
on a wave to the same point on the next wave.
• Usually crest to crest, or trough to trough.
• We measure wavelength in micrometers (µm)
• 1 µm = one millionth of a meter
• Frequency: the number of waves per
second (usually measured in Hz).
• Since all electromagnetic energy travels at
the same speed, as wavelength increases,
the frequency decreases.
• This is an inverse relationship.
• Light is only a small part of the
electromagnetic spectrum.
Radio Telescopes
• Radio telescopes gather radio waves from
distant stars, nebula, galaxies, and
planets.
– Radio waves are not affected by weather
– They are not distorted by time of day, clouds,
pollution, or the atmosphere.
– They can detect information not detected by
optical telescopes
– They can map and detect neutral hydrogen to
determine the shapes of galaxies.
Very Large Array (VLA), National Radio Astronomy Observatory
is a group of 27 bowl-shaped radio antennas. Each antenna is 25
metres (82 feet) across. When used together, they make one
very powerful radio telescope.
Radio Interferometry
• Multiple radio telescopes combined for
greater resolving power.
• The greater the distance between
telescopes the greater the accuracy.
• The more telescopes used, the greater the
accuracy.
• A group of telescopes used together is
called an array.
VLA (Very Large Array) in New Mexico
• Gamma-rays and x-rays are also being
used to study our universe.
NASA’s Chandra X-Ray Observatory
• In this composite image of spiral galaxy M106
Radio data from the Very Large Array
appears as blue, X-ray data from Chandra is
coded red, and infrared data from the Spitzer
Space Telescope appears green. The
anomalous arms appear as purple and blue
emission.
• Only 35,000 light years away lies W49B, the supernova remnant left
over from the cataclysmic burst. New evidence pointing to a gamma
ray burst origin for this remnant was discovered by X-ray data from the
Chandra X-ray Observatory, combined with infrared observations from
the Palomar 200-inch telescope in southern California.
• The discovery is exciting for two reasons. It may be the first time a
supernova remnant from a gamma-ray burst has been found so close
to Earth. It also appears to be tied to a special type of black hole called
a "collapsar," which was first theorized by scientists more than a
decade ago.
Space Probes
• Unmanned satellites or remote controlled
landers.
• Probes have been sent to all planets but
Pluto. The only other object in the solar
system to be physically explored by man,
except for Earth, is the moon. This was
first accomplished by the Apollo 11
Mission in 1969.
• Space Probes
Sounds of Jupiter
There are two types of Optical
Telescopes:
1. Refracting telescopes:
– Use 2 lenses
– Limited to 1m diameter
Yerkes telescope in Wisconsin is
Largest refracting telescope in the word
Label the Refracting telescope
2. Reflecting Telescopes:
– Use concave mirrors
– One of the largest reflecting mirrors in the
world is in Russia and has a diameter of 6m.
– Segmented mirrors are used to make even
more powerful reflecting telescopes.
Keck observatory on Mauna Kea, Hawaii
The 10 m segmented mirror of the Keck Telescope
Interferometry
• Using a combination of telescopes
together to obtain more detailed images of
distant objects
The European Southern
Observatory
Hubble Space Telescope
• A reflecting telescope orbiting 600 Km
above the Earth.
• 13m in length and 4.4m in diameter
• 1 trip around the Earth takes 95min.
• HST has discovered many galaxies not
visible from Earth.
• New discoveries are constantly being
made.
• See Hubble ppt in MS Data
• Hubble's Top 10 Photos
• Hubble--The-amazing-space-photographsuniverse
3.3
Using Technology to Interpret
Space
Measuring Distance
• Triangulation
– By measuring the angles between a baseline
and the target object (such as a tree or tower)
you can determine the distance to that object.
– You must know the length of one side of the
triangle (baseline) and the measures of the
two angles at each end of the baseline.
– See P. 447
• Parallax
– The apparent shift in position of an object
when the object is viewed from two different
places.
– Astronomers use a star’s apparent shift in
position relative to the background stars to
determine what angles to use when
triangulating the stars distance from Earth.
• With triangulation, the longer the baseline,
the more accurate the results.
• The longest baseline we can use from
Earth is the diameter of the Earth’s orbit.
• The measurement is taken 6 mo. Apart.
Determining a Star’s Composition
• White light is a combination of all colours
and can be separated into its component
colours (visible spectrum).
• Light is a form of energy and is only part of
the electromagnetic spectrum.
Shorter wavelength
Longer wavelength
• When light from a star is refracted distinct
dark bands in a distinct sequences and
thicknesses appear in their spectra.
• Each element in a star absorbs light at
different wavelengths creating its own
“signature” spectra.
• By analyzing the spectra of refracted light
from a star with an instrument called a
spectroscope astronomers can determine
the composition of the star.
Example of Stellar Spectra
Determining a Star’s Direction
• The Doppler Effect
– Sound waves become compressed in front of
a moving object and stretched behind it.
– This makes the pitch higher as the object
moves towards you and lower as it moves
away from you.
Doppler Effect at the Race Track Video
• Like sound, light also travels in waves and
is affected by the Doppler effect.
• Changes in the wavelength of light can be
used to measure how fast and in what
direction a light emitting object is moving.
• The dark spectrum lines of an approaching
star will be shifted to the blue side of the
spectrum as the wavelengths of light are
being compressed.
• For a star moving away from the Earth the
dark lines will be shifted to the red side of
the spectrum as the light waves are being
stretched.
• The Doppler effect is used in radar guns
by the police to measure the speed of
vehicles, as well as by weather networks
to predict storms