Destination:

1. Destination: A Planet like Earth Caty Pilachowski IU Astronomy Mini-University, June 2011 Caty Pilachowski Mini-University 2011

2. Very Rare Rare Common Very Common Very Rare Rare Common Very Common Are We Alone? How common is life of any kind in the Milky Way? How common is intelligent, technological life?

3. Our Journey • An Astronomer’s View of the Solar System • Searching for Exoplanets • Our Solar System may not be typical… • Planets in Bulk – The NASA Kepler Mission • Finding Earth-like Planets

4. Our Solar System Big Gas Planets Little Rocky Planets Medium Ice Planets

5. Planet Sizes The Sun Jupiter The Earth Little, rocky planets near the Sun Big gas planets far from the Sun

6. Planet Orbits Are Near-Circles But not perfect circles!

7. Planets Orbit in the Same Direction The Sun spins the same way!

8. Planets (mostly) spinthe same way they orbit except for some… “Obliquity”

9. Nearly Planets are Co-Planar ^

10. Describing our Solar System Planet orbits are nearly circular Planets orbit in the same direction Planet orbits are close to the same plane Planets mostly spin the same way as the Sun Is our solar system typical?

11. More than 500 “exoplanets” discovered since 1995 HOW? Line of Sight Velocity Changes Transits Imaging Gravitational Lensing Wobbles in stars’ positions

12. Star Velocities VERY high precision is needed to measure these very small velocity changes Stars’ line of sight velocities change slightly as planets orbit

13. Planetary Transits If the Earth lies in the same plane as the orbit of a planet we see a transit • The planet passes across the face of the star • Some of the starlight is blocked by planet and the star appears dimmer

14. Seeing planets near stars is hard Voyager I image taken in 1990 from 4 billion miles from the Sun The Sun is a billion times brighter than Jupiter From Alpha Centauri, Jupiter is only 4 arc-seconds from the Sun

15. Imaging planets is hard! • “A” is the star GQ Lupi • “b” is a possible planet • “b” is 250 times fainter than the star • “b” is roughly 100 astronomical units distant from GQ Lupi • “b” is about 2 x Jupiter’s mass

16. Selection Effects How we search affects what we find Velocity method finds massive & close-in planets Transits find all sizes, but smaller ones are harder to confirm Imaging technique favors large, far-out planets Techniques, sensitivity are improving

17. The First Exoplanets! Hot Jupiters! Distance from star

18. Sizes Jupiter Super-Jupiters The Sun The Earth

19. Is Our SS Typical? • Hot Jupiters • Multi-planet systems • Far out planets • Orbits not circular These hot Jupiters probably form further out, and migrate inward as they eject smaller bodies from their planetary systems

20. Is Our SS Typical? • Hot Jupiters • Multi-planet systems • Far out planets • Orbits not circular

21. Is Our SS Typical? • Hot Jupiters • Multi-planet systems • Far out planets • Orbits not circular

22. Is Our SS Typical? Location of brown dwarf (blocked out) • Hot Jupiters • Multi-planet systems • Far out planets • Orbits not circular Brown Dwarf 2M1207 @ 225 LY 50 AU Possible planet ~5 x Jupiter’s mass

23. Fomalhaut’s Planet An exoplanet in Fomalhaut’s dust belt 115 AU Fomalhaut is 25 light years from the Sun

24. HR 8799 Planetary System • Planets at 2, 5 and 10 o’ clock • 10, 10 and 7 times the mass of Jupiter • 24, 37 and 67 times the Earth-sun separation from the host star. (The star is blocked out) HR 8799 is 140 light years away

25. Is Our SS Typical? • Hot Jupiters • Multi-planet systems • Far out planets • Orbits not circular Not Circular Circular Distance from Star

26. How Common are Earth-like Planets? The NASA Kepler Mission

27. Kepler Stares at Cygnus Kepler monitors the brightness of 150,000 stars to find transits Kepler determines planet size planet temperature Followup observations to get masses, densities, orbits

28. Kepler’s Targets Are Nearby Our sun is in the Orion arm of our galaxy Kepler’s targets are between 500 and 3,000 light years away

29. Confirmed Kepler Planets

30. Kepler 11 – at least 6 planets!

31. Kepler 11 Very compact! • All six planets are larger than Earth • The largest are the size of Uranus and Neptune • All six would nearly fit within the orbit of Mercury

32. Are Kepler 11 Planets like Ours? Water World!

33. Kepler 10b Is Rocky • 1.4 times the size of Earth • Too hot for life – 2500 Farenheit • 20 times closer to its star than Mercury is to ours

34. From Iron to Styrofoam Temperature 2800 F Mass 0.4 x Jupiter Radius 1.5 x Jupiter Kepler 7B

35. Kepler has found more than 1200 candidate planets Kepler measures the slight dimming of starlight caused by a planet crossing the face of its parent star 1,235 candidate planets orbiting other suns found since 2009 Kepler's planet candidates are shown to scale The Sun, Earth, and Jupiter

36. Kepler Has Lots of Candidates

37. Not all of Kepler’s candidates will be real planets…

38. Properties of Kepler Planets

39. Giant Planets and Tiny Planets • 1 in 20 has an Earth-like planet • 1 in 14 has a super-Earth planet • 1 in 5 has a Neptune-like planet • 1 in 40 has a Jupiter-sized planet

40. What Does Kepler Tell Us?? 34% of stars like the Sun have planets Many of those stars have multiple planets Most planets are much smaller than Jupiter But are any like Earth????

41. The Habitable Zone The region around a star where water can exist as a liquid on the surface of a planet Far out on hot stars, close in on cool stars

42. A planet needs the right star! Stable planetary orbit Old enough star Big enough habitable zone Stable brightness Even so… billions of stars in the Milky Way seem to offer at least the possibility of habitable worlds

43. Some Kepler Candidates Are Possible

44. A Kepler Estimate… Maybe 70 million Earth-like planets Maybe 1 million in the habitable zone Somewhere out there… A Planet like Earth?

45. Very Rare Rare Common Very Common Very Rare Rare Common Very Common Are We Alone? How common is life of any kind in the Milky Way? How common is intelligent, technological life?

46. Further Information • Books suggested in the Mini booklet… • Websites • Exoplanets.org • Kepler.nasa.gov • en.wikipedia.org/wiki/Extrasolar_planet Powerpoint available at: www.astro.indiana.edu/catyp/miniu.html Kirkwood Obs. open 10:30 – 11:30 on Wednesday (weather permitting)