Optical TelescopesLACC: § 5.1, 4, 5
• Optical Telescopes: Refracting vs. Reflecting
• Reflecting Telescopes: prime vs. Cassegrain vs. Newtonian vs. Coudé
• Q: Why make telescopes so big?
Telescope technology is primarily about detecting objects that are normally too dim or outside the
range of human vision.
1Thursday, February 18, 2010
Optical Telescopes
http://www.meade.com/support/telewrk.html
Refracting* Primary Lens *
Reflecting* Primary Mirror *
Catadioptric* Both *
2Thursday, February 18, 2010
Reflecting Telescopes
http://138.238.143.191/astronomy/Chaisson/AT405/HTML/AT40501.htm
3Thursday, February 18, 2010
Why Make Telescopes Big?
http://www.jwst.nasa.gov/comparison.html
Areacircle = π•radius2
So, a telescope with twice the diameter (or radius) will have four times the light collecting area. 10x the diameter would mean 100x the light collecting area.
James Webb Space Telescope (JWST)
4Thursday, February 18, 2010
Why Make Telescopes Big?
http://www.physast.uga.edu/~rls/astro1020/ch7/ovhd.html
"Angular resolution" = smallest angular separation where you can still see that 2 objects are actually 2 objects rather than 1 blobby object• The human eye's angular
resolution = 1 arcminute• The Hubble Space Telescope's
ang. resolution = 0.05 arcseconds
5Thursday, February 18, 2010
Adaptive Optics
http://www2.ifa.hawaii.edu/newsletters/article.cfm?a=300&n=1
Temperature fluctuations in Earth's atmosphere act like small, randomly sized and oriented weak lenses that cause stellar images to degrade and dance (twinkle), limiting the resolution and sensitivity of ground-based telescopes. "Seeing," as these effects are called, varies with the site and conditions but never vanishes. The only way to avoid it is to launch a telescope into space. Mauna Kea and, to a lesser extent, Haleakala have better seeing than most observatory locations, yet even at these exceptional sites, the atmosphere turns pinpoint sources of light (such as stars) into slightly fuzzy blobs.
Adaptive Optics (AO) System: The deformable mirror changes shape to remove the distortions in the lightwave
before the light goes to the camera.
6Thursday, February 18, 2010
Optical TelescopesLACC: § 5.1, 4, 5
• Optical Telescopes: Refracting vs. Reflecting
• Reflecting Telescopes: prime vs. Cassegrain vs. Newtonian vs. Coudé
• Q: Why make telescopes so big?A: Light Gathering Power
Angular Resolution (alternatives--Interferometry, Adaptive Optics)
Telescope technology is primarily about detecting objects that are normally too dim or outside the
range of human vision.
7Thursday, February 18, 2010
LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,
3rd ed.
• Ch. 5, pp. 131-132: 3. Give two reasons.
Due at the beginning of the next class period.
Test covering chapters 1-5 next class period.
8Thursday, February 18, 2010
Observing the Entire EM Spectrum LACC: § 5.1, 4, 5
• Telescopes: Designs
• Our Atmosphere: Optical (Infrared) and Radio Atmospheric Windows
• Space: Interstellar Dust is Transparent to Infrared and Radio
Telescope technology is primarily about detecting objects that are normally too dim or outside the
range of human vision.
9Thursday, February 18, 2010
The EM Spectrum
http://www.nhn.ou.edu/~jeffery/course/c_energy/energyl/lec001.html
• Credit: Philip Ronan who has given permission to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version.
• Download site: Wikipedia: Image:EM spectrum.svg.
10Thursday, February 18, 2010
EM Rad. & Earth’s Atmosphere
http://www.answers.com/topic/telescope?cat=technology
11Thursday, February 18, 2010
Radio Telescopes
http://www.skyscan.ca/RadioTelescopes.htm
All radio telescopes are ground based.
Why?
12Thursday, February 18, 2010
Radio image
http://antwrp.gsfc.nasa.gov/apod/ap020218.html
Shells of ancient supernovas, cocoons surrounding newborn stars, and specks from distant quasars highlight this tremendous vista.... The representative color image covers about 10 degrees across on the sky ... in radio light. Diffuse bands of ionized gas flow though a dominating region of
star formation, located about 6000 light-years away. Two prominent supernova shells visible include the brown globule on the lower left and the white bumpy sphere on the upper right. Prominent stellar cocoons are visible throughout the image as bright white knots. Far in the
distance, visible here as only red dots, quasars glow.
13Thursday, February 18, 2010
Interferometry
http://www.geocities.com/plasminojen/astro/radio_astronomy.html
Powerful arrays of telescopes, like the Very Large Array (VLA) in New Mexico, can be coordinated in such a way as to "see" radio sources and having the effect of a single dish nearly 20 miles across.
14Thursday, February 18, 2010
Infrared Telescopes
http://www.skyscan.ca/RadioTelescopes.htm
Earth’s atmosphere blocks much of the infrared radiation that comes from space. Placing
telescopes in orbit overcomes this problem; but for
infrared astronomy, it’s not absolutely
necessary.
NASA's Stratospheric Observatory for Infrared Astronomy
15Thursday, February 18, 2010
http://www.sciencenewsforkids.org/articles/20100106/Note3.asp
http://photojournal.jpl.nasa.gov/catalog/PIA12832http://antwrp.gsfc.nasa.gov/apod/ap061228.html
The Wide-field Infrared Survey Explorer (WISE) is the latest
Infrared Telescopes
visible light infra red
moon shown for scale
16Thursday, February 18, 2010
Visible vs. Infrared
http://www.spitzer.caltech.edu/Media/happenings/20051208/
Warm dust becomes visible when viewed in the ir. (So ir telescopes must be cooled.)
Remember: interstellar dust blocks visible light, but not ir.
17Thursday, February 18, 2010
X-Ray Telescopes
http://www.geocities.com/wt2002friendz/schoolwork/telescope_gina_mei.html
Earth’s atmosphere blocks the x-ray radiation that
comes from space. For this reason, all x-ray telescopes
are placed in orbit.
18Thursday, February 18, 2010
X-Ray Image
http://apod.nasa.gov/apod/ap991028.html
Spanning over 25,000 light-years, comparable to the distance from the Sun to the center of our own Milky Way galaxy, a cosmic jet seen in X-rays blasts from the center of Centaurus A. Only 10 million light-years away, Centaurus A is a giant elliptical galaxy - the closest active galaxy to Earth. This composite image illustrates the jumble of gas, dust, and stars visible in an optical picture of
Cen A superposed on a new image recorded by the orbiting Chandra X-ray Observatory. The X-ray data is shown in red. Present theories hold that the X-ray bright jet is caused by electrons
driven to extremely high energies over enormous distances. The jet's power source is likely to be a black hole with about 10 million times the mass of the Sun coincident with the X-ray bright
spot at the galaxy's center.
19Thursday, February 18, 2010
Gamma Ray Telescopes
http://imagine.gsfc.nasa.gov/docs/science/how_l2/gamma_detectors.html
Solid state gamma ray detectors in space or
optical reflecting telescopes to detect
evidence of air showers.
20Thursday, February 18, 2010
Gamma Ray Image
http://www.mpi-hd.mpg.de/hfm/HESS/pages/press/old/PressRelease/LS5039Press-2005/LS5039_Press_E.htm
Top: High Energy Stereoscopic System (H.E.S.S.) telescopes in Namibia, in South-West Africa. This system of four 13 m diameter telescopes is currently the most sensitive detector of very high energy gamma-rays.Center: A larger picture of the gamma ray sky as measured with H.E.S.S.Bottom Left: The green star shows the position of LS5039 as measured using radio telescopes, and the white ellipse shows the gamma ray position. In the upper-left corner ... HESS J1825-137.Bottom Right: A computer simulation of the microquasar LS5039, showing one possible scenario where gamma rays are generated in microquasar 'jets'.
21Thursday, February 18, 2010
Observing the Entire EM Spectrum LACC: § 5.1, 4, 5
• Telescopes: Designs requirements for: radio, infrared, visible/uv, x-ray, gamma ray
• Our Atmosphere: Optical (Infrared) and Radio Atmospheric Windows
• Space: Interstellar Dust is Transparent to Infrared and Radio
Telescope technology is primarily about detecting objects that are normally too dim or outside the
range of human vision.
22Thursday, February 18, 2010
LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe,
3rd ed.
• Ch. 5, pp. 131-132: 7. The different regions of the spectrum are: radio, microwave, infrared, visible, ultraviolet, x-ray, gamma ray.
Due at the beginning of the next class period.
Test covering chapters 1-5 next class period.
23Thursday, February 18, 2010
Review for the Test 1 of 5:Observational Astronomy
[10 pts] The History of Astronomy• shape (Aristotle) and size (Eratosthenes) and of the
Earth• Geocentric (Ptolemy) vs. Heliocentric
(Copernicus), Galileo• Kepler (3 Laws or Planetary Motion), Newton (3
Laws of Gravity, Universal Gravity)
[10 pts] Making use of the Heavens• Know the Celestial Sphere: RA, Dec, meridian,
zenith, N/S Poles, Celestial Equator• Understand how the 23.5° axial tilt of the Earth
affects the motion/position of celestial objects: Arctic/Antarctic Circle, Tropic of Cancer/Capricorn
• Know how the heavens can be used to mark time: moon phases, eclipses, solar/sidereal day
[10 pts] Electromagnetic Radiation • Understand how energy, frequency, and wavelength
relate to each other: v = f λ, E=hf• Know the order of the electromagnetic spectrum:
radio, microwave, ir, visible, uv, x-ray, gamma ray• Know how photon interact with atoms: energy
levels, types of spectra--continuous, absorption, emission line
[10 pts] Telescopes• Understand how the different kinds of optical
telescopes work: refracting vs reflecting--prime, Cassegrain, Newtonian, Coudé; and non-optical telescopes: radio, infrared, X-ray, gamma ray
• Understand how the Earth’s atmosphere affects observations (atmospheric windows--visible, radio) and telescope design (which ones can’t be ground based--gamma ray, X-ray, ultraviolet)
• Understand how telescopes are built to improve their light gathering ability and angular resolution (large primary mirrors, adaptive optics, interferometry)
[10 pts] Figures/Illustrations• Understand orbital mechanics and moon phases• Use a graphic showing the energy levels around an
atom to determine what photon energies could be absorbed/emitted; ID elements in a spectrum
• ID the type of telescope (refracting; reflecting--prime, Cassegrain, Newtonian, Coudé, radio, infrared, X-ray, gamma ray) or spectra (continuous/thermal, emission line, absorption line) from a picture
24Thursday, February 18, 2010