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Homework #2 Notes

Learn about different types of telescopes used to observe various wavelengths in space, including infrared, ultraviolet, X-ray, gamma-ray, and radio telescopes. Understand their advantages, challenges, and the future of astronomy in space.

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Homework #2 Notes

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  1. Homework #2 Notes Average: (35.3/40 (88.3%) High: 40/40 (100%) • Some of you are still not reading the question all the way through and not answering multi-part questions. • Some of you are still carrying way to many digits to the final answer – will begin to penalize starting on Exam #1. • Seeing some mixing/matching of units in calculations where constants are defined in a specific unit system, i.e., G, σ.

  2. Transmission in Atmosphere • Only radio and visible light pass easily thru Earth’s atmosphere • Telescopes in space needed to observe other wavelengths, energies Courtesy: The Cosmic Perspective by Bennitt,Donahue,Schneider,Voit

  3. Infrared & Ultraviolet Telescopes IR and UV telescopes are like optical telescopes but must be above atmosphere Spitzer SOFIA

  4. SOFIA: A flying observatory Spectroscopy from 1-800 μm Star-forming regions at 10 K - 1000 K. US-German project in a Boeing 747SP with a 2.5m telescope First light: May 26, 2010.

  5. X-Ray Telescopes X-ray telescopes must be above the atmosphere Chandra

  6. X-Ray Telescopes Special mirrors to focus X-ray photons by grazing reflections Recall: X-rays act more like particles than waves. Think of X-rays “skipping” off the mirror surface like a stone skipping off the surface of a lake.

  7. Gamma-Ray Telescopes • Gamma-ray telescopes also must be in space • Focusing gamma-rays well still to be solved! Compton

  8. Radio Telescopes A radio telescope is a reflecting telescope for radio waves At certain radio wavelengths, observing can be done in the middle of the day. Arecibo Observatory Puerto Rico

  9. Antennae Interacting Galaxies X-ray: 10 million degree gas + X-ray binaries Near infrared: older stars Optical (HST) Radio: star formation/ supernovae Infrared: dust in star forming region

  10. Multiple telescopes can work together Very Large Array (VLA) Socorro, NM

  11. Interferometry 2+ telescopes have angular resolution of a single large one! An interferometer has the angular resolution but not the collectingarea of a much larger telescope.

  12. Interferometry Recall: diffraction limit  /D (without interferometry, very poor spatial resolution for radio telescopes) • Easiest at radio wavelengths • Starting to do with IR and visible-light telescopes Michigan InfraRed Combiner= MIRC Very Large Array (VLA) Socorro, NM

  13. Very Long Baseline Interferometer (Earth) Makes images of 0.001” resolution (much better than Hubble, but only for radio sources).

  14. Future of Astronomy in Space? The Moon would be an ideal observing site No atmosphere No radio stations No light pollution Earth-Moon could be a giant interferometer

  15. End of material covered on Exam #1

  16. Exam #1 First midterm on Thursday, September 27 (in class) ~ 40% multiple choice (test your qualitative understanding of topics covered + simple math problems) ~ 30% short answer (1-2 sentences typically), mostly qualitative ~ 30% quantitative problems (like the homework) Material from the book NOT covered in class will NOT be on the exam.

  17. Exam #1 Exam will cover material through Chapter 6 (Telescopes). Closed book, but you may bring one sheet of paper with equations on it (equations only – no concepts). Don’t forget to bring your calculators! All constants/other relevant numbers will be provided to you. We will play AstroJeopardy today. You will be divided into teams, with the winning team earning some extra credit for the exam.

  18. Exam #1 – Office Hours Today: 3:00 – 4:30 PM Wednesday: noon – 1:30PM Thursday: 8:15AM – 9:15AM

  19. Astro Jeopardy Rules • Teams consisting of 2-3 members. 2) Winning team member will split 12 percentage points on Exam 1, second place team will split 6 percentage points. 3) Answers MUST be in the form of a question. 4) When an individual rings in, he/she CANNOT consult with team member (exception: Final Jeopardy). If an answer is missed, a teammate of the person who gave the incorrect answer CANNOT ring in.

  20. Astro Jeopardy Rules 5) Teams waiting to buzz in after an incorrect answer must wait for the system to be reset. 6) Incorrect answers WILL cost your team points. 7) For Daily Doubles, you may wager any value up to your current score or question value (whichever is larger). Teammates can confer on the $ amount of the wager, but cannot give answers to the individual who picked the Daily Double. 8) Under no circumstance may you refer to me as “Alex”.

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