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Tuesday September 25, 2012. ( Telescopes; HTUW: Alien Galaxy Parts 2 & 3 ). The Launch Pad Tuesday, 9/25/12. Please pick up your graded work off of the side table as you come in. List the four types of galaxies, their relative abundance in the Universe, and their relative sizes. spirals
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TuesdaySeptember 25, 2012 (Telescopes; HTUW: Alien Galaxy Parts 2 & 3)
The Launch Pad Tuesday, 9/25/12 Please pick up your graded work off of the side table as you come in. List the four types of galaxies, their relative abundance in the Universe, and their relative sizes. spirals barred spirals ellipticals irregulars 30% 10% 60% 10% large very large small or huge varies
The Launch Pad Tuesday, 9/25/12 Identify barred spiral galaxy horsehead dark nebula
Announcements • None Today
Recent Events in Science Hubble Catches Glowing Gas and Dark Dust in a Side-On Spiral http://www.sciencedaily.com/releases/2012/09/120924093957.htm ?? Read all about it! The NASA/ESA Hubble Space Telescope has produced a sharp image of NGC 4634, a spiral galaxy seen exactly side-on. Its disk is slightly warped by ongoing interactions with a nearby galaxy, and it is crisscrossed by clearly defined dust lanes and bright nebulae.
Video How the Universe Works: Alien Galaxy Part 2 – Studying the Progress of Galaxies (6:06 – 10:43)
Optical (Visible Light) Telescopes • An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum. • Optical telescopes increase the apparent angular size of distant objects as well as their apparent brightness. • In order for the image to be observed, photographed, studied, and sent to a computer, telescopes work by employing one or more curved optical elements, usually made from glass lenses and/or mirrors, to gather and bring that light to a focal point.
Optical (Visible Light) Telescopes The two main types of optical telescopes are: Refracting telescopes Reflecting telescopes
Refracting Optical Telescopes Refracting telescopes use a lens (called the objective) to bend (refract) the light to produce an image. Light converges at an area called the focus. The eyepiece is a second lens used to examine the image directly. Refracting telescopes have an optical defect called chromatic aberration (color distortion.)
Reflecting Optical Telescopes Reflecting telescopes use a concave mirror to gather the light, and there is no color distortion. Nearly all large telescopes are of this type.
Optical Resolution The Andromeda Galaxy using telescopes of different resolution.The top picture is not “out of focus”, it’s a resolving issue, not a focus problem.
Deployment of the Hubble Space Telescope in Earth Orbit April 24, 1990 Figure 23.17
Radio Telescopes Radio wavelength radiation reaches Earth’s surface, so radio telescopes can be Earth-based.
Radio Telescopes Radio telescopes are “big dishes” used to gather radio wavelength electromagnetic radiation.
Radio Telescopes Radio telescopes have to be very large in order to gather radio waves, which are about 100,000 times longer than visible radiation waves. They are often made of a wire mesh, and have rather poor resolution. Radio telescopes can be wired together into a network called a “radio interferometer.”
A steerable radio telescope at Green Bank, West Virginia Figure 23.15 A
Radio Telescopes Radio telescopes have several advantages over optical telescopes: • they are less affected by weather • they are less expensive to build and maintain • they can be used 24 hours a day • they are able to detect material that does not emit visible radiation • and, they can “see” through interstellar dust clouds
Microwave Telescopes The Milky Way as the bright center area, with the cosmic microwave background left over from the Big Bang shown as the orange mottling at the top and bottom edges of the image. The Planck Microwave telescope
Infrared Telescopes These telescopes capture radiation in the infrared bands of the Electromagnetic Spectrum, therefore they are “seeing” heat rather than visible light. The Helix Nebula in infrared. Spitzer Infrared Space Telescope
Ultraviolet Telescopes Our Sun in Ultraviolet The Hopkins Ultraviolet Telescopes
X Ray Telescopes • The supernova remnant Cassiopeia A in X Ray The Chandra X Ray Observatory
Gamma Ray Telescopes • a gamma-ray image of the entire sky taken over four days by Fermi • The Fermi Gamma-ray Space Telescope
Video How the Universe Works: Alien Galaxy Part 3 – Black Hole in the Middle of the Milky Way Galaxy (10:44 – 17:39)