10/7/03Prof. Lynn Cominsky1 Class web site: Office: Darwin 329A and NASA E/PO (707) Best way to reach me: Astronomy 305/Frontiers in Astronomy

10/7/03Prof. Lynn Cominsky2 Astrobiology Questions (3 weeks) Is there life elsewhere in our Solar system? Is there life elsewhere in our Solar system? Are Earth-like planets common? Are Earth-like planets common? Are we alone? Are we alone?

10/7/03Prof. Lynn Cominsky3 Group 6

10/7/03Prof. Lynn Cominsky4 Are Earth-like planets common?

10/7/03Prof. Lynn Cominsky5 Question to ponder: When will Voyager get to the next star? It was launched in 1977 and has just passed Pluto. A) 2020 AD B) 8200 AD C) 82,000 AD D) 182,000 AD

10/7/03Prof. Lynn Cominsky6 Answer Voyager is travelling about 37,000 mph, which is about c/20000 Voyager is travelling about 37,000 mph, which is about c/20000 The nearest star (Proxima Centauri) is about 4 light years away The nearest star (Proxima Centauri) is about 4 light years away It will therefore take about 80,000 years to reach Proxima Centauri It will therefore take about 80,000 years to reach Proxima Centauri The correct answer is therefore C The correct answer is therefore C

10/7/03Prof. Lynn Cominsky7 Planets around other stars Over 100 planets around other stars are known

10/7/03Prof. Lynn Cominsky8 Planets around other stars  PSR (a radio pulsar, Wolczan 1995)  3 objects orbiting this stellar corpse  1 is the size of the Moon  2 are the size of the Earth  probably formed after the supernova explosion that made the pulsar  51 Pegasi (Sun-like star, Mayor and Queloz 1996)  at least one object, about 1/2 of Jupiter  orbit of only 4 days  closer to star than Mercury, so very hot  42 light years from Earth

10/7/03Prof. Lynn Cominsky9 Planets around other stars  70 Virginis (Sun-like star, Marcy and Butler 1996)  116 day orbit  9 Jupiter masses (1 Jupiter = 317 Earth masses)  temperature of planet may allow liquid water to exist  78 light years from Earth  47 Ursae Majoris (Marcy and Butler 1996)  1100 day orbit  3 Jupiter masses  temperature of planet may allow liquid water to exist  44 light years from Earth

10/7/03Prof. Lynn Cominsky10 Another solar system Upsilon Andromedae: Multiple planet solar system discovered by Marcy et al. a) 4.6 d b) 240 d c) 1313 d Ups And

10/7/03Prof. Lynn Cominsky11 How they find extra-solar planets Stars are too bright to see reflected light from planets directly Stars are too bright to see reflected light from planets directly Unseen planet causes star to wobble as it orbits – star’s light is Doppler shifted Unseen planet causes star to wobble as it orbits – star’s light is Doppler shifted

10/7/03Prof. Lynn Cominsky12 Doppler Shift Wavelength is shorter when approaching Stationary waves Wavelength is longer when receding

10/7/03Prof. Lynn Cominsky13 Doppler Shift Comparison of laboratory to blue-shifted object Comparison of laboratory to red-shifted object

10/7/03Prof. Lynn Cominsky14 Doppler Shift Doppler shift song by AstroCapella Doppler shift song by AstroCapella

10/7/03Prof. Lynn Cominsky15 Other methods: Astrometry – measuring the exact position of a star as it wobbles Astrometry – measuring the exact position of a star as it wobbles Hipparcos was an ESA satellite operational from

10/7/03Prof. Lynn Cominsky16 Other methods: Photometry – measuring the change in brightness of a star as a planet transits in front of it, obscuring some of the light (~2%) Photometry – measuring the change in brightness of a star as a planet transits in front of it, obscuring some of the light (~2%)

10/7/03Prof. Lynn Cominsky17 The first transiting planet HD – a visualization by Aurore Simonnet HD – a visualization by Aurore Simonnet

10/7/03Prof. Lynn Cominsky18 The first transiting planet STARE project found the first transit in HD – Brown and Charbonneau 1999 STARE project found the first transit in HD – Brown and Charbonneau 1999 The planet’s mass is 63% of Jupiter (about 200 Earth masses) with radius 1.3 times Jupiter  density 0.39 g/cm 3 (< water!) The planet’s mass is 63% of Jupiter (about 200 Earth masses) with radius 1.3 times Jupiter  density 0.39 g/cm 3 (< water!) It transits the star every 3.5 days It transits the star every 3.5 days Its atmosphere is very hot (1100 o C) since it is only 6.4 million km from the star Its atmosphere is very hot (1100 o C) since it is only 6.4 million km from the star When the planet passed in front of the star, the star’s light passed through the planet’s atmosphere and sodium was observed by HST When the planet passed in front of the star, the star’s light passed through the planet’s atmosphere and sodium was observed by HST

10/7/03Prof. Lynn Cominsky19 Saturn mass planets (95 times Earth) Both planets are very close to their stars - This makes them easier to detect Both planets are very close to their stars - This makes them easier to detect If each planet orbited the Earth’s Sun: If each planet orbited the Earth’s Sun:

10/7/03Prof. Lynn Cominsky20 Latest news (7/03) (See exoplanets.org) 110 planets are now known outside our solar system 110 planets are now known outside our solar system Earlier searches preferentially found closer orbiting planets, more massive planets and eccentric orbits (“hot Jupiters”) – now smaller planets are being found in orbits that are closer and more circular Earlier searches preferentially found closer orbiting planets, more massive planets and eccentric orbits (“hot Jupiters”) – now smaller planets are being found in orbits that are closer and more circular Jupiter-analog found around HD70642 Jupiter-analog found around HD70642 Sub-Saturn planet found around HD 3651 Sub-Saturn planet found around HD 3651

10/7/03Prof. Lynn Cominsky21 Iron abundance vs. planets The probability that a star harbors a planet depends on the star's metal content. The probability that a star harbors a planet depends on the star's metal content.

10/7/03Prof. Lynn Cominsky22 Inventing Alien Life forms This activity is from the Univ. of Washington /activities/aliens.html This activity is from the Univ. of Washington /activities/aliens.html /activities/aliens.html /activities/aliens.html Take one dice for each group of 2 students and try the evolution experiment to create your own alien. The rolling of the dice reproduces the random elements in evolution. Take one dice for each group of 2 students and try the evolution experiment to create your own alien. The rolling of the dice reproduces the random elements in evolution. When you have finished, draw a picture of your alien and give it a a name When you have finished, draw a picture of your alien and give it a a name

10/7/03Prof. Lynn Cominsky23 Inventing Alien Life forms Write a paragraph that has the following information: Write a paragraph that has the following information: Describe the environment your creature needs to survive. Describe the environment your creature needs to survive. Where in our solar system would you be most likely to find such a creature? Where in our solar system would you be most likely to find such a creature? What sort of food source might your creature need? What sort of food source might your creature need? Is your creature alone in its environment? If not, how does it coexist with other species? Is your creature alone in its environment? If not, how does it coexist with other species?

10/7/03Prof. Lynn Cominsky24 Web Resources Voyager mission Voyager mission Extra-solar planet searches Extra-solar planet searches STARE: html STARE: html html html Latest news: (and a cool interactive) Latest news: (and a cool interactive) Hipparcos Space Astrometry Mission Hipparcos Space Astrometry Mission