Starry Monday at Otterbein

1. Welcome to Starry Monday at Otterbein Astronomy Lecture Series -every first Monday of the month- May 5, 2008 Dr. Uwe Trittmann

2. Today’s Topics • How to find Life in the Universe • The Night Sky in May

3. On the Web • To learn more about astronomy and physics at Otterbein, please visit • http://www.otterbein.edu/dept/PHYS/weitkamp.asp (Observatory) • http://www.otterbein.edu/dept/PHYS/ (Physics Dept.)

4. How to find Life in the Universe • What is Life? • How to detect Life? • Where to look for Life? • Life vs. Intelligent Life

5. What is Life? • Has a metabolism • Uses energy • Reacts to changes in the environment • Reproduces • … • Transforms its environment • Changes to environment hopefully observable

6. What kind of Life? • Focusing on carbon – liquid water based life • Carbon as a chemically unique element • (Liquid) Water as a powerful solvent and reactant • Assuming lower life-forms, we cannot expect life to actively produce signals • Look for life on the surface of a rocky planet

7. Water • Phase diagram of water dictates temperature and pressure range for liquid Minimal pressure: 610 Pa -18º C: life on Earth exists +123º C: life on Earth exists

8. Where to look for Life? • Where you can find (detect) it ;-) • If carbon-liquid water based life exists on the surface of a planet • Planet must have atmosphere for liquid water to exist • Planet must receive enough energy from host star to liquify water Planet must be in the habitable zone (HZ) of its host star

9. Definition of “Habitable Zone” • Region around a star where stellar radiation maintains liquid water over a substantial part of the surface of a rocky planet • Note: planet must be big enough to hold on to its atmosphere, and possibly replenish it through outgassings from its interior.

10. Extend of HZ depends on time • Sun gets brighter as it ages • Planets orbits change over time • Planets rotational axis inclination changes • Early Solar system: • Venus, Earth in HZ, Mars partially • Now: • Earth, Mars in HZ

11. Habitats beyond the HZ • Temperature, pressure too low  go to interior of planets/moons • Earth: 5km under surface liquid water can exist • Tidal heating: gravitational distortions will heat interior of (soft) moons • Io  Volcanism driven by Jupiter • Europa  liquid water under ice? • Saturn’s Titan • Methane/Nitrogen based geology/climate at -180°C Not on surface of Planet  Hard to detect!

12. Greenhouse Effect affects Climate • Earth absorbs energy from the Sun and heats up • Earth re-radiates the absorbed energy in the form of infrared radiation • The infrared radiation is absorbed by carbon dioxide and water vapor in the atmosphere Typically happens and stabilizes climate on planet harboring life Good, because life takes at least a billion years to develop/ have effects on planet

13. The biggest effect life had on Earth • Shakespeare? • Building the Great Wall of China? • Explosion of the Hiroshima bomb? • Transforming Carbondioxide into Oxygen! (Zero oxygen 3 billion years ago, now 21%)

14. Chances of detecting Life • How far away is the nearest Earth-like planet?  19 ly (if 3% of stars have ELPs) • Is it habitable? • Atmosphere • Rocky • Carbon/Water available • shielded from heavy bombardment

15. How to detect Life • Life produces oxygen, methane • Can detect ozone (made from O2), Methane via its characteristic infrared radiation • Plants use photosynthesis: chlorophyll rejects colors not utilized (utilizes visible frequencies) IR red-edge • TV & Radio signals  1992: Galileo spacecraft detects life on Earth (and not on the Moon)!

16. (Very) Intelligent Life • Looking for extra-terrestrial intelligence, we can relax our assumptions (neither carbon nor water-base necessary) • We are looking for signals of civilizations rather than signs of life

17. Classification of Civilizations • Type I: uses energy sources of their planet including solar radiation arriving at their planet (us!) • Type II: uses a large part of the total radiation of their sun (shows up as reddening of the star’s spectrum) • Type III: uses a large part of the energy production of their galaxy (might rearrange galaxy)

18. Galactic Exploration • John von Neumann: build self-replicating space probe that builds many replicas of itself once it finds suitable conditions, send them on their way • Can colonize galaxy in only 100 million years (less than 1% of lifespan) • O’Neill colonies

19. Fermi Paradox • If ETI exists it must be widespread • If it’s widespread, why aren’t they among us? • ETI must have had plenty time to occur • Maybe they do not exist • Maybe we didn’t look hard/long enough? • Maybe they are among us?

20. Signals • Probably electromagnetic waves • Easy to generate • not exceedingly absorbed by interstellar medium, planetary atmospheres • Information can be imprinted on them with minimal energy cost • Travels fast (but not fast enough?!) • We are detectable since 12. December 1901

21. Green Bank (or Drake) Equation • Estimated number of technological civilizations present in the Milky Way galaxy is given by the average rate of star formation  fraction of stars having planetary systems  average number of planets within the habitable zone for various types of star and star system  fraction of habitable planets that develop life  fraction of life-bearing planets on which intelligence appears  fraction of intelligent life forms that develop technology  average lifetime of a technological civilization • Could be 100 to 1 billion (?)

22. Illustration of Drake Equation

23. Time is of the Essence • A lot of things can go wrong in “cosmic instances” like a few thousand years • It is “guesstimated” that a technological civilization might last about 3000 years

24. Extinction of the Dinosaurs • Possibly caused by impact of a large meteorite • Large amount of dust thrown into atmosphere, causing global cooling, disruption of the food chain • Evidence: • Iridium layer found in fossil record at about time of extinction of dinosaurs • Large numbers of species become extinct at about the same time • Crater in Yucatan may be “the one” • Are extinctions periodic?

25. SETI • If average lifetime is 1 million years, then the average distance between civilizations in the galaxy is 150 ly • Thus 300 years for messages to go back and forth • Communications via radio signal • Earth has been broadcasting in RF range for most of this century • Earth is brighter than the Sun in radio • 18–21 cm wavelength range good for interstellar communication • SETI search is ongoing • SETI@Home: http://setiathome.ssl.berkeley.edu • If they exist, should we contact them?

26. SETI with Radio Telescopes • Radio frequencies are used because • Civilizations are likely to use these frequencies • We can observe them from the ground • Biggest radio telescope is in Arecibo, Puerto Rico

27. CETI – Talking to Aliens • How can we communicate? • Put up a big sign (?!) • Send a (radio) signal • Send a space probe with a message • Should we try to communicate?

28. Our Messages to the Aliens • Golden plate with essential info on humans • On board Pioneer 10 space probe • Started in the 70’s • past solar system

29. Our EM Message to the Aliens • In 1974 sent radio signal from Arecibo to globular cluster M13 (300,000 stars, 21,000ly away) • Brighter than the Sun • “The signal, transmitted at 2380 megahertz with a duration of 169 seconds, delivered an effective power of 3 trillion watts, the strongest man-made signal ever sent.”

30. The Night Sky in May • Nights shorter and EDT => later observing! • Spring constellations are up: Cancer, Leo, Big Dipper • Mars, Saturn dominate early evening, Jupiter early morning.

31. Moon Phases • Today: New Moon • 5 / 11 (First quarter Moon) • 5 / 19 (Full Moon) • 5 / 27 (Last Quarter Moon) • 6 / 3 (New Moon)

32. Today at Noon • Sun at meridian, i.e. exactly south

33. 10 PM Typical observing hour, early May • Saturn Mars

34. Zenith • Big Dipper points to the north pole

35. South • Saturn near Praesepe (M44), an open star cluster • Oops, that was last year! Now Saturn is here!

36. South • Spring constellations: • Leo • Hydra • Crater • Sextans

37. East • Canes Venatici: • M51 • Coma-Virgo Cluster • Globular Star Clusters • M3, M5

38. East Virgo and Coma with the Virgo-Coma galaxy cluster

39. Virgo-Coma Cluster • Lots of galaxies within a few degrees

40. M87, M88 and M91

41. East • Hercules • Corona Borealis • Bootes • Globular Star • Clusters: • M 3 • M 13 • M 92

42. M13: Globular Cluster These guys will know of our existance in 21,000 years!

43. Mark your Calendars! • Next Starry Monday: June 2, 2008, 8 pm (this is a Monday ) • Observing at Prairie Oaks Metro Park: • Friday, May 9, 2008, 9:00 pm • Web pages: • http://www.otterbein.edu/dept/PHYS/weitkamp.asp (Obs.) • http://www.otterbein.edu/dept/PHYS/ (Physics Dept.)