ASTR-1010 Planetary Astronomy

1. ASTR-1010Planetary Astronomy Day - 26

3. Announcements Smartworks Chapter 9-12: Due Tuesday, Dec. 14 @1030 am Final Exam: 1030-1230 Tuesday Dec. 14 Visit to the Observatory & Virtual Observations Reports due Today

4. Extrasolar Planets Most of the extrasolar planets discovered to date are quite massive and have orbits that are very different from planets in our solar system

5. Astronomers have discovered planets orbitingother stars • Geoff Marcy is using the 10-meter Keck telescope in Hawaii to measure the Doppler effect in stars that wobble because of planets orbiting around them • So far, he and other teams have found more than 100 extrasolar planets

6. How do you Find Exo-Planets? • 3 Methods • Radial velocity shifts of the parent star • Direct Imaging • Transits

7. Finding Extrasolar Planets • The planets themselves are not visible; their presence is detected by the “wobble” of the stars around which they orbit

8. Radial Velocity

9. 1st Direct IR Images

10. 1st direct Optical Image

12. A Transit

13. USING PHOTOMETRYTO DETECT PLANETS • Transits Planet crosses line of sight between observer and star and blocks a small amount of light from the star Transit of Mercury in 2003 Transit of HD 209458 observed with HST 13

15. Searching for Extrasolar Planets • This chapter primarily deals with searching for extrasolar planets and the techniques for finding them. Most of this information is available in the text and various sites on-line, such as: http://en.wikipedia.org/wiki/Extrasolar_planet

17. Mass (M)‏ Luminosity (L)‏ Lifetime inbillion years 17.5 52,500 0.01 2.0 14 1.1 1.0 1.0 10 0.67 0.15 53 0.21 0.011 290 Main Sequence Lifetimes

18. Life, the Universe, & Everything • Evolution is a normal consequence of physics. • If a self-replicating molecule ever forms, then complex structures will arise. • Reproduction via heredity is not perfect; there are always mutations. • Natural selection: well-adapted molecules (or organisms) will have more surviving offspring than less well-adapted ones.

21. Are We Alone? Estimate the number of advanced civilizations using the Drake Equation. Multiply: • number of stars in our galaxy • fraction of stars with planets • average number of planets per star • fraction of planets with life • fraction that develop advanced technology • Result is the likelihood such planets exist today.

22. The Drake Equation • We know several numbers in the Drake equation, particularly the astronomical ones. • For others, we have to guess. • Optimistic values: nearest civilization only 40 light-years away. • Pessimistic values: distance is 30 million ly.

23. The Drake Equation • 1961 – 1st SETI conference, Green Bank, WV • Number of civilizations in our galaxy (or the Universe at large) from which we could potentially get a signal. • Does NOT give a definitive answer. • Rather, it lays out the factors that are important in determining this number.

24. The Drake Equation • Number of Civilizations = NHP X flife X fciv X fnow • NHP -Number of habitable planets in galaxy • flife -Number of habitable planets that have life • fciv -Fraction of life-bearing planets where a civilization capable of IS communication at some time has arisen. • fnow -Fraction of habitable planets with civilization now, not in the past.

26. Concept Quiz –Life in the Universe Even if there’s a very low chance that any one planet has life on it, there may be many advanced civilizations because … • There are billions of billions of stars in the universe. • Simple life inevitably leads to complex life. • We know that Earth-like planets are common in our galaxy.

27. 4 Metabolic Classifications • Based on energy and carbon acquisition. • 1. Photoautotrophs • 2. Chemoautotrophs • 3. Photoheterotrophs • 4. Chemoheterotrophs

30. Is Intelligence Widespread? • If life is widespread, what about intelligence? • SETI is only successful if THEY communicate. • Homo sapiens have only started to understand the environment and explore the cosmos in the last <500 years. • Suggests a long period of evolution is required to produce technologically intelligent creatures. • Chance events • body plans in Cambrian explosion • K-T extinctor

31. Convergent Evolution • The tendency of organisms of different evolutionary backgrounds that occupy similar ecological niches to resemble each other. • Large marine predators – dolphins & sharks • Eyesight (eyes evolved eight times).

32. Encephalization Quotient (EQ)‏ • Raw brain power based on brain mass. • Simple measure • EQ = 1 line – general intelligence • Above line – capable of elaborate behavior • Below line – less mentally agile

34. Evolution of Intelligence • Humans don't have the largest brains. • Is the largest in relation to body mass.

35. Early SETI • Marconi (1874-1937)‏ • Tesla (1856-1943)‏ • Both claimed to have heard aliens on the radio. • Probably “whistlers” • Low frequencies which don't penetrate atmosphere.

36. Modern SETI - Origins • 1959 – Cocconi & Morrison – Cornell Univ. • Galaxy is older than solar system, so could be civilizations around linger than ours. • Band –Frequencies receiver is sensitive to. • Bandwidth – a particular freq. in the band. • Governed by how much information is transmitted.

37. SETI - Today • Categories of Signals • Local communications on other world. • Communications between home world & other site. • Intentional signal beacons. (Project Ozma) • In theory, SETI can detect all three types. 26m dish at NRAO-Green Bank

38. Our Own Signals • Broadcast in ~1950, just past 50 ly distance. • High power, high-frequency TV • > 2000 stars in this volume. • Star map

40. A Signal Look for: repetition, prime numbers … 1974 – signal sent to M13 (bad choice in hind sight). – 21,000 ly distant.

41. SETI - Today • Current SETI projects

43. Radio –vs.– Optical • Radio is a logical choice since we developed radio capability early (didn’t everyone?) • Dust blocks light in the denser parts of the Galactic plane. • Limits our view to a few hundred parsecs. • Not as big an issue today. • But how? • Laser pulses - doesn’t everyone know Morse code? • Lick – 500 ly search distance • Harvard also has a project going.

44. Artifacts • 2001: A Space Odyssey • The TMA is clearly not natural.

45. Artifacts • Parking spaces – Lagrange points • Manufacturing plants.

46. Types of Civilizations • Nikolai Kardashev – 20th century Planetary (Type I) – use resources of home planet. Stellar (Type II) – corral resources of home star. Galactic (Type III) – employ resources of entire galaxy. • We’re in the first category. • What would be the hallmark of the third? “Any sufficiently advanced technology is indistinguishable from magic.” – Sir Arthur C. Clarke

47. Type II Civilizations • Dyson Sphere Freeman Dyson • Could detect the IR radiation

48. Big Question • What if we succeed in finding another civilization? • Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence Sistilli NASA experience Jill Tarter at Arecibo

49. UFOs • Project Bluebook • Day the Earth Stood Still • War of the Worlds • Mars Attacks