We are not alone: Other planets, other...

Edmund Bertschinger

MIT Department of Physics andKavli Institute for Astrophysics and

Space Research

We are not alone: Other planets, other earths?

2

3

Earth and Mars – or Mars and Earth?

4

Life on Mars?

R. Villard, STScI

5

Martian Meteorite found in Antarctica

McKay et al. 1996: carbonate globules – evidence for microbial life? Probably not.

Lunar and Planetary Institute

6

Mars Global Surveyor: fresh water?

7

8

9

Family Portrait: 4 rocky planets, 2 gas giants, 2 ice giants

10

11

Planets around other stars: exoplanetsAs of December, 2006:

209 planets183 Doppler shift

4 microlensing14 transits

4 imaging4 pulsar timing

12

As of July 22, 2008

307 confirmed planets

Detected by Doppler shifts: 290249 planetary systems (29 multiple planet systems)

Transiting planets (found initially by Doppler): 52Detected by microlensing: 7Detected by imaging: 5Detected by timing: 3 systems containing 5 planets

13

How to find other planetary systems

Doppler measurement of stellar wobble: planets’ gravity pulls on star

14

Figure from California-Carnegie Planet SearchFirst success: 1995, Mayor and Queloz

15

How to find other planetary systems

Transit: planet passes in front of star, dims the light a tiny amount

16

Both the Doppler and Transit methods can much more easily find close-in, Jupiter mass planets

than earth-like planets

Space Telescope Science Institute

17

How to find other planetary systems

Gravitational Microlensing

18

The gravity of a planet orbiting a star causes

light rays to bend, changing the amount of light reaching the

earth.

Background star

Enhanced image at

earth

25 January 2006: the star OGLE-2005-BLG-390L has a planet of mass about 10 earth masses, in a 10-year orbit!

(very similar to Neptune)

19

How to find other planetary systems

Direct imaging

20

21

Family Comparison

22

Family Comparison

R. Villard, STScI

23

What have we learned?

Jupiter

24

Jupiter

What have we learned?

25

What have we learned?

Mercury

Hot Jupiters

26

What have we learned?

Stars with more heavy

elements are more likely to

host planets

(California -Carnegie

Planet Search)

27

What have we learned?

Some planets likely

have right conditions for liquid

water(it’s 300K in here!)

28

J.F. Kasting et al.

Habitable zone for life

Darren Williams, Penn State Erie

29

J.F. Kasting et al.

Extrasolar planets

Habitable zone for life

Darren Williams, Penn State Erie

30

Future: search for earthlike planets and life

Search method: transits using satelliteESA Corot mission launched 2007.NASA Kepler: 2/2009 launch scheduledMIT/Harvard TESS: proposed wide-field survey mission.

Terrestrial Planet Finder: 2015 or later

Atmospheric Spectroscopy

31

Additional Credits and InformationCredits:

Prof. Josh Winn, MITWater on Mars: antwrp.gsfc.nasa.gov/apod/ - Astronomy

Picture of the DaySahara Desert and Mars: Lunar and Planetary InstituteBlack hole embedding diagram: Scott Hughes, MITFigures showing Mean Orbital Distance created online at

http://extrasolar.net/charts.aspKepler and TPF: NASA/Jet Propulsion Laboratory

Books:Origins: Fourteen Billion Years of Cosmic Evolution, Neil

deGrasse Tyson and Donald GoldsmithEarth: An Intimate History, Richard ForteyThe Ancestor’s Tale: A Pilgrimage to the Dawn of Evolution,

Richard Dawkins

32

Websites for more information

www.alma.info – ALMA gateway

Extrasolar.net – General information about exoplanets

Exoplanets.org – California-Carnegie exoplanet searches

www.astrobio.net - Astrobiology

Solstation.com – General astronomy information, sky maps

antwrp.gsfc.nasa.gov/apod/ - Astronomy Picture of the Day