Astronomy 1010 Planetary Astronomy Fall_2014 Day-22

Course Announcements SW Ch. 6: Wed. 10/22 (it changed) Read chapter 7 Dark Night Observing Monday Oct. 20 Exam-2 will be returned on Friday. If you’re one of the ones who did not take it last week, you have until the start of class on Friday to do so.

Spectrum But visible light is only one type of electromagnetic radiation (light) emitted by stars Astronomers are truly interested in the entire spectrum of Light!

 The atmosphere does not transmit all light.  Nearly all X-ray, ultraviolet, and infrared wavelengths are blocked.  Satellites are needed for these wavelengths.

Consider This Class as Seen in Different Wavelengths of Light!

Orion in Infrared!

HST Views of Orion Nebula showing stars hidden in clouds

Observations at other wavelengths are revealing previously invisible sights UV Ordinary visible Infrared Map of Orion region

 Radio telescopes are large, steerable parabolic dishes with antennas.  Allow astronomers to study radio waves.  Wavelengths of a centimeter to about 10 meters.  Radio waves can pass through gas and dust.

Radio wavelength observations are possible from Earth’s surface

Observing with Radio Waves Long Wavelength…poor resolution

Under the dish at Arecibo

The Very Large Array (VLA)

 Single radio telescopes have poor resolution due to the long wavelengths.  Interferometric arrays combine the signals from many telescopes, increasing resolution.

 Two electromagnetic waves in the same location will produce interference.  The waves will either enhance or detract from each other, resulting in constructive or destructive interference.  This can result in spectral dispersion. CONNECTIONS 6.2

 Airborne observatories: raise the telescope above clouds and water vapor (infrared astronomy).  Satellites in orbit: detect wavelengths that the atmosphere blocks (ultraviolet and X-rays).  Can produce very sharp images (e.g., the Hubble Space Telescope).

Astronomers use different instruments to look at light of different wavelengths - sometimes, we even have to go above Earth’s atmosphere. That Darned Atmosphere

Lecture Tutorial: Telescopes & Earth’s Atmosphere: pg. 51 Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now!!!! Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group.

Concept Quiz—Mountain Telescopes Why do astronomers build telescopes on mountains? A.to be closer to the objects they are observing B.to minimize the effects of the atmosphere C.to observe wavelengths such as X-rays or ultraviolet light

Concept Quiz—Telescopes Pick the incorrect answer: Why build telescopes on the ground when we can launch them into space? A.Ground-based telescopes are useful for studying visible and infrared light. B.Ground-based telescopes get much higher resolution. C.They are far cheaper to build and fix than space-based telescopes.