telescopes & electromagnetic radiation · refracting telescope perfected by galileo uses lenses...
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Telescopes
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Focus Question:
How do astronomers study light?
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Telescopes
Tools for collecting and analyzing
electromagnetic radiation (light) in ways
beyond what we can do with our eyes alone
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Properties of Telescopes
Aperture: how well the telescope can collect the light.
Larger aperture = more light collected (brighter image)
Resolution: The ability to distinguish small details of objects
http://www.ifa.hawaii.edu/users/lin/ast110-6/applets/angular_resol_car_lights.htm
Magnification: how much it can magnify the image.
Depends on combination of lenses/mirrors
Not as important
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Optical Telescopes
Studying Visible light
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Refracting Telescope
Perfected by Galileo
Uses lenses to gather and bend visible light
Can be a combination of convex (curved outward) or concave (curved inward) lenses
A primary lens collects light and sends it to a smaller secondary lens at the back of the telescope tube.
Not used much today
Primary Lens Secondary Lens
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Refracting Telescope:
Yerkes Observatory
A 40 inch refracting telescope is located inside the Yerkes Observatory at University of Chicago.
It was created in 1897 and remains the largest refracting
telescope ever used.
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Reflecting telescopes
First developed by Isaac Newton
Focus light by “bouncing” it off of mirrors
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A Better Type of Reflector
A Cassegrain design uses a second mirror to reflect the
light back through a hole in the primary mirror
Invented in 1672, this design is the most common in
research telescopes today.
The detector(s) can be placed behind the mirror in a
convenient location for making adjustments
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There are currently thirteen working telescopes near
the summit of Mauna Kea:
nine for optical and infrared astronomy
three for submillimeter wavelength (microwave) astronomy
one for radio astronomy
Mauna Kea Observatories
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The Keck Observatory: A Ground-Based Optical Telescope
Mauna Kea, Hawaii
Twin telescopes with 10m wide mirrors that work together
World’s largest optical telescope until 2009 –
now the biggest single reflector is the Gran Telescopio Canarias (GTC) in Spain
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Keck Headquarters
Astronomers don’t actually work at the telescopes on the
summit
They sit in the “remote operations room” in the town of
Waimea, about 2 hours away and the data is sent to a
computer
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Model of Keck I
Primary Mirror
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My new buddy David, who
works at both Keck
headquarters in Waimea
and at the telescopes on
Mauna Kea
The grass area
behind us
represents one
of the mirror
segments
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Problems with Ground-based telescopes
Earth’s atmosphere reflects or absorbs certain
wavelengths
our atmosphere and magnetic field serves as a shield for x-
rays, gamma rays and most UV light
Earth’s atmosphere blurs images the bending of light by the atmosphere depends on the
temperature of the “air”
“twinkling” (shimmering) effect
“Light pollution” from artificial light sources make it
hard to see very faint objects in space
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Getting Better Images
Telescopes are built on mountaintops so
that they are above much of the
atmosphere
Telescopes are built in remote areas
where there isn’t much artificial light
Modern ground-based telescopes use
two newtechnologies:
Interferometry
Adaptive Optics
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Interferometry
Technique of using an array of telescopes to collect multiple beams of light at one time High resolution (detail)
Used to observe very distant or faint objects
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Computer-controlled mirror supports adjust the mirror surface
many times per second to compensate for distortions by
atmospheric turbulence and increase resolution power
Adaptive Optics
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Other Types of Telescopes
Beyond visible light
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Beyond Visible Light…
Many modern day telescopes do not use visible light to
collect images
They collect other wavelengths of light from the
Electromagnetic Spectrum: radio waves, x-rays, infrared, etc
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Ground-Based Radio Telescopes
A large dish or network of dishes focus the energy of
radio waves on to a small receiver
Largest telescopes ever constructed
Examples:
ALMA - Atacama Large Millimeter Array
Atacama desert in Chile
66 networked radio telescopes
VLA-Very Large Array
New Mexico
27 networked radio telescopes
Arecibo Observatory
Puerto Rico
Largest ever built-- 1000 ft across, 167 ft deep, covers 20 acres of land
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Space-Based Telescopes
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Space-Based Telescopes
Advantages:
No distortion by Earth’s atmosphere
Able to study all wavelengths of light
Disadvantages:
Expensive to launch and maintain
Difficult to repair
Short life span
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Hubble Space Telescope
Launched in 1990, orbits
380 miles above Earth
Named for American Astronomer
Edwin Hubble (1889-1953) who
discovered the expansion of the
universe
Reflecting telescope - Collects
visible light, infrared, and ultraviolet
Primary mirror is 8 feet across
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Chandra X-ray Telescope
NASA launched it in 1999
Orbits Earth 200 times higher
than Hubble
Resolving power: equal to reading
a road sign from 12 miles away
Contains special grazing-incidence
mirrors (because x-rays can pass
through normal mirrors)
Looks at quasars, binary stars, and
black holes
Spiral galaxy M106
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Other Space Telescopes
Spitzer – infrared light
Fermi- Gamma Ray
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Telescopes of the Future…
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James Webb Telescope
A large infrared telescope
Will be launched in 2018
6.5 meter mirror
Longer wavelength
coverage and better
sensitivity than the
Hubble
Will observe galaxy &
star formation and
potential for life on
other planets
James Webb video clip
Building the JWST
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Thirty Meter Telescope (TMT)
Proposed ground-based telescope with a 30-meter
primary mirror, the largest ever built
Planned for construction on Mauna Kea in 2015 but
delayed and surrounded in controversy after protesters
blocked the site
Incredible resolution would allow astronomers to study
very faint and distant objects and learn about:
Star formation
Exoplanets
Supermassive black holes
Evolution of the universe
http://www.cnn.com/2015/08/27/us/tmt-hawaii-telescope-
controversy/index.html
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“A 30-meter telescope, operating in
wavelengths ranging from the ultraviolet to
the mid-infrared, is an essential tool to
address questions in astronomy ranging
from understanding star and planet
formation to unraveling the history of
galaxies and the development of large-scale
structure in the universe.” -- TMT
website
Potential Scientific Advancement
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Mauna Kea is home to many archaeological burial sites
Shrines and temples are located near the summit
Modern Native Hawaiians continue to regard Mauna Kea with
reverence and many cultural and religious practices are still
performed there.
Cultural/religious beliefs
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Community support: malama means “take care of” or “protect”
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Land Rights: The upside-down Hawaiian Flag
symbolizes the belief that Hawaii was illegally
annexed by the US in 1959
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$1.4 Billion construction project
Estimated 300 temporary construction jobs
120 permanent jobs once the facility opens
Hawaii’s economy has struggled since the 2008
crash
Greater financial impact
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Possible damage to the habitat of the Wekiu bug, an indigenous
insect that was just recently removed from the endangered
species list
The Silversword plant species became an endangered species
due to cattle, sheep, and goats lower on the mountain
Potential for contamination of the Mauna Kea aquifer, which
supplies water to the east side of Hawaii Island
Environmental Impact
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Should the TMT be built on Mauna Kea?
What do You think?
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The Latest News…
As of October 30th, 2016 the TMT Board of Governors
has identified a site in the Canary Islands of Spain as the
primary alternative to Hawaii.
In January 2017, a state circuit court judge ordered a new
hearing allowing residents to contest the issuance of a
building permit on public lands
"Mauna Kea continues to be the preferred choice for the
location of the Thirty Meter Telescope, and the Board will
continue intensive efforts to gain approval for TMT in
Hawaii.”
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http://www.hawaiinewsnow.com/story/31193881/thirty-
meter-telescope-officials-considering-sites-outside-of-
hawaii