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Class web site: Class web site: http://http://glastglast

.sonoma.edu/~lynnc/courses/a305.sonoma.edu/~lynnc/courses/a305

Office: Darwin 329A and NASA E/POOffice: Darwin 329A and NASA E/PO

(707) 664-2655(707) 664-2655

Best way to reach me: Best way to reach me: lynnc@charmian.sonoma.edulynnc@charmian.sonoma.edu

Astronomy 305/Frontiers in Astronomy 305/Frontiers in AstronomyAstronomy

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Astrobiology Questions (3 Astrobiology Questions (3 weeks)weeks)

Is there life elsewhere in our Solar Is there life elsewhere in our Solar system?  system?  

Are Earth-like planets common?  Are Earth-like planets common?   Are we alone?Are we alone?

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Group 6Group 6

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Are Earth-like planets common?Are Earth-like planets common?

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Question to ponder: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

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AnswerAnswer

Voyager is travelling about 37,000 Voyager is travelling about 37,000 mph, which is about c/20000mph, which is about c/20000

The nearest star (Proxima The nearest star (Proxima Centauri) is about 4 light years Centauri) is about 4 light years awayaway

It will therefore take about 80,000 It will therefore take about 80,000 years to reach Proxima Centauriyears to reach Proxima Centauri

The correct answer is therefore The correct answer is therefore CC

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Planets around other starsPlanets around other stars

Over 100 planets around other stars are known

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Planets around other starsPlanets around other stars

PSR 1257+12 (a radio pulsar, Wolczan 1995)3 objects orbiting this stellar corpse1 is the size of the Moon2 are the size of the Earthprobably 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

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Planets around other starsPlanets 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

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Another solar systemAnother 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

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How they find extra-solar How they find extra-solar planetsplanets

Stars are too bright to see reflected Stars are too bright to see reflected light from planets directlylight from planets directly

Unseen planet causes star to wobble as Unseen planet causes star to wobble as it orbits – star’s light is Doppler shiftedit orbits – star’s light is Doppler shifted

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Doppler ShiftDoppler Shift

Wavelength is shorter when approaching

Stationary waves

Wavelength is longer when receding

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Doppler ShiftDoppler Shift

Comparison of laboratory to blue-shifted objectComparison of laboratory to blue-shifted object

Comparison of laboratory to red-shifted object

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Doppler ShiftDoppler Shift

Doppler shift song by AstroCapellaDoppler shift song by AstroCapella

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Other methods:Other methods:

Astrometry – measuring the exact Astrometry – measuring the exact position of a star as it wobblesposition of a star as it wobbles

Hipparcos was an ESA satellite operational from 1989-93

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Other methods:Other methods:

Photometry – measuring the change in Photometry – measuring the change in brightness of a star as a planet transits brightness of a star as a planet transits in front of it, obscuring some of the light in front of it, obscuring some of the light (~2%)(~2%)

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The first transiting planetThe first transiting planet

HD209548 – HD209548 – a visualization by Aurore a visualization by Aurore SimonnetSimonnet

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The first transiting planetThe first transiting planet

STARE project found the first transit in STARE project found the first transit in HD209548 – Brown and Charbonneau 1999HD209548 – Brown and Charbonneau 1999

The planet’s mass is 63% of Jupiter (about The planet’s mass is 63% of Jupiter (about 200 Earth masses) with radius 1.3 times 200 Earth masses) with radius 1.3 times Jupiter Jupiter density 0.39 g/cm density 0.39 g/cm3 3 (< water!)(< water!)

It transits the star every 3.5 daysIt transits the star every 3.5 days Its atmosphere is very hot (1100Its atmosphere is very hot (1100ooC) since it is C) since it is

only 6.4 million km from the staronly 6.4 million km from the star When the planet passed in front of the star, When the planet passed in front of the star,

the star’s light passed through the planet’s the star’s light passed through the planet’s atmosphere and sodium was observed by atmosphere and sodium was observed by HST HST

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Saturn mass planets (95 times Saturn mass planets (95 times Earth)Earth)

Both planets are very close to their Both planets are very close to their stars - This makes them easier to detectstars - This makes them easier to detect

If each planet orbited the Earth’s Sun:If each planet orbited the Earth’s Sun:

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Latest news (7/03) Latest news (7/03) (See (See exoplanets.org)exoplanets.org)

110 planets are now known outside our 110 planets are now known outside our solar systemsolar system

Earlier searches preferentially found Earlier searches preferentially found closer orbiting planets, more massive closer orbiting planets, more massive planets and eccentric orbits (“hot planets and eccentric orbits (“hot Jupiters”) – now smaller planets are being Jupiters”) – now smaller planets are being found in orbits that are closer and more found in orbits that are closer and more circularcircular

Jupiter-analog found around Jupiter-analog found around HD70642HD70642 Sub-Saturn planet found around Sub-Saturn planet found around HD 3651HD 3651

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Iron abundance vs. Iron abundance vs. planetsplanets The probability that a star harbors a planet The probability that a star harbors a planet

depends on the star's metal content.depends on the star's metal content.

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Inventing Alien Life formsInventing Alien Life forms

This activity is from the Univ. of This activity is from the Univ. of WashingtonWashington http://www.astro.washington.edu/labs/clearinghhttp://www.astro.washington.edu/labs/clearinghouse/activities/aliens.htmlouse/activities/aliens.html

Take one dice for each group of 2 Take one dice for each group of 2 students and try the evolution students and try the evolution experiment to create your own alien. The experiment to create your own alien. The rolling of the dice reproduces the random rolling of the dice reproduces the random elements in evolution.elements in evolution.

When you have finished, draw a picture When you have finished, draw a picture of your alien and give it a a nameof your alien and give it a a name

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Inventing Alien Life formsInventing Alien Life forms

Write a paragraph that has the following Write a paragraph that has the following information:information: Describe the environment your creature Describe the environment your creature

needs to survive. needs to survive. Where in our solar system would you be Where in our solar system would you be

most likely to find such a creature? most likely to find such a creature? What sort of food source might your What sort of food source might your

creature need? creature need? Is your creature alone in its environment? If Is your creature alone in its environment? If

not, how does it coexist with other species?not, how does it coexist with other species?

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Web ResourcesWeb Resources

Voyager missionVoyager mission http://vraptor.jpl.nasa.gov/voyager/voyager.htmlhttp://vraptor.jpl.nasa.gov/voyager/voyager.html

Extra-solar planet searchesExtra-solar planet searcheshttp://exoplanets.orghttp://exoplanets.org

STARE:STARE: http://www.hao.ucar.edu/public/research/stare/shttp://www.hao.ucar.edu/public/research/stare/stare.htmltare.html

Latest news:Latest news: (and a cool interactive)(and a cool interactive) http://planetquest.jpl.nasa.gov/news/tau1_gruis.http://planetquest.jpl.nasa.gov/news/tau1_gruis.htmlhtml

Hipparcos Space Astrometry MissionHipparcos Space Astrometry Mission http://astro.estec.esa.nl/Hipparcos/http://astro.estec.esa.nl/Hipparcos/