Download Non-Optical Telescopes

Why look at different
frequencies of light?
• Cooler objects are only visible at long
wavelengths: radio, microwaves, IR.
• Hotter objects are only visible at short
wavelengths: UV, X-rays, -rays.
Radio Telescopes
• Detects cool gases: H+ H H2
• Can detect molecules out in space:
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•
•
•
•
oxygen O2
carbon dioxide CO2
hydrogen cyanide HCN
formaldehyde H2CO
Ethanol CH3COOH
Advantages / Problems
• Operates night or day
• Atmosphere doesn’t absorb radio waves
• Poorest resolution of any type of light
(doesn’t see details well)
• Solution is to make antennas (dishes)
VERY large
Arecibo Radio Telescope, Arecibo, Puerto Rico
Puerto Rico
Green
Bank
Telescope
Green Bank,
W.Va.
The dish
would hold
Fulton Field
Radio Interferometry – a Recipe
• Take 2 (or more) widely separated radio
telescopes…
• Electronically blend their signals…
• Result is as if you had a telescope with a
diameter equal to the distance between the
two separate telescopes.
• VASTLY improves resolution!
Very Large Baseline Array sites across the US. Together these
telescopes form a huge interferometer.
Infrared (IR) Telescopes
• Very similar to visible wavelength
telescopes, except for the detector, called a
bolometer.
• IR scopes detect heat from warm gas or
warm objects. “Warm” means not hot
enough to glow in visible light.
• These scopes must be kept very cold or the
heat the scope itself radiates swamps out
what they’re looking for.
What kinds of objects?
• IR telescopes “see” warm gas, molecules &
dust. In some cases, they can look through
cooler dust to see what’s inside the dust
clouds!
• Since stars form where there’s lots of dust,
these scopes are great for looking inside
dusty nebulas where new stars form.
We can’t see everything just in
visible wavelengths !!
ISO – the
Infrared
Space
Observatory
European
Space
Agency (ESA)
Orbital Telescopes
• Why put a telescope in orbit?
• Gets it above the atmosphere with all its
dust, ozone, water vapor, and CO2 that
absorb so much of what we want to see.
• What’s the most famous orbiting telescope?
If you said the Hubble Space Telescope
or HST, you’re right!
HST does detect visible light
• It also detects ultraviolet light.
• 2.4 meter mirror = 230,400 eyes!
• Resolution is 0.0126 arcsecond or
1 / 3,500,000th of a circle.
• We’re used to seeing photos like these!
X-ray & Gamma Telescopes
• “Sees” very hot objects:
• Black Holes
• Pulsars & Neutron Stars
• Supernovas
• VERY good resolution – sees fine
details
NGC 4261 – a huge black hole
at the center of a distant galaxy
A supernova – an exploding star
What’s left after the explosion – a supernova remnant.
This one’s called Cassiopeia A.
The Crab Nebula in visible light (left) & X-rays (right).
At the center of the Crab Nebula – a PULSAR