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Exoplanets: the Search for Another Earth By Ben Waxer.

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1 Exoplanets: the Search for Another Earth By Ben Waxer

2 Habitable Zone Aka Goldilocks' Zone The range of a planet’s orbit around its star that allows the existence of liquid water Liquid water is a requirement of life Too close to the sun = too hot Too far from the sun = too cold

3 Types of Exoplanets Gas Giant Hot Jupiter Super Earth Terrestrial Unknown

4 Gas Giants Very massive Thick atmosphere of hydrogen and helium Core of rocky elements Hydrogen and helium constitutes most of the planet or only an outer envelope

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6 Hot Jupiters Subset of gas giants Similar characteristics to Jupiter Orbits very close to their stars Incredibly high surface temperatures Most common known form of extrasolar planet Easy to detect

7 Super Earths Defined by mass only 1.9 – 10 Earth masses Debate over how to further classify them

8 Terrestial Aka rocky planet Composition of silicate rocks or metals Solid planetary surface Central iron metallic core Silicate mantle Generally smaller and harder to detect Many more detected with Kepler

9 Needle in a Haystack Radial Velocity variations 10 cm/s Transit depths 10^-4 Astrometric variations 0.1 microarcseconds Contrast ratios of 10^-10 and 10^-7

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11 Search for Exoplanets 1706 planets around 1036 stars 442 systems with multiple planets 415 Gas Giants 1008 Hot Jupiters 193 Super Earths 80 Terrestrial Planets 10 Unknown Planets

12 Kepler space telescope March 2009 – August 2013 surveyed 100,000 stars in constellation Cygnus used transit method to detect planets could detect planets 30-600 times less massive than Jupiter has confirmed 942 exoplanets and 2903 candidates

13 Methods of Detection Doppler Effect Transit Gravitational Microlensing Many others to a lesser extent

14 Doppler Shift Radial Velocity Method Measures velocity changes Star and planet orbit center of mass Easier to detect close, massive planets Hard to detect Earth-sized planets Has found 499 planets

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16 Transit Planet transits in between star and observer Small dip in star brightness Period of dip gives planet orbit Depth of dip gives planet size Method used by Kepler and CoRoT spacecraft Has found 1126 planets

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18 Gravitational Microlensing Light from Source star gets amplified as it is bent around the lens star Amount of amplification grows with degree of alignment Planet forms a binary lens with lens star Causes caustics -> lightcurve variations

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20 Average fraction of microlensing source stars – LMC = 1.2*10^-7 – Bulge = 2.43*10^-6 Einstein radius Amplification Factor Better detects low mass planets Must monitor millions of stars Only have one (short) try and can easily miss it if your timings off u = Lens-source angular separation / Einstein Radius

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22 Searching for Life Mass and Radius -> Density Compare to Models -> Planet Structure Alternatively observe spectra and search for biosignatures – Planned for James Webb Space Telescope

23 Interesting Exoplanets Tau Bootis b KOI-314c Messier 67 Kepler 186 f

24 Tau Bootis b Hot Jupiter Water vapor found in atmosphere 51 light years away Analyzed faint spectra emitted by planet Found unique signature of water

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26 KOI-314c Approximately the mass of Earth Orbits a red dwarf star Large, ‘puffed-up’ atmosphere 1.6 times the radius of Earth Blurs the line between rocky planets and gas giants

27 Messier 67 Three planets in star cluster 2600 light years away Detected ‘wobble’ using radial velocity method Two hot jupiters and one gas giant One hot jupiter orbits a star nearly identical to the sun

28 Kepler 186 f 500 light years away Most promising candidate In Habitable Zone of its M type star 1.1 times the size of Earth Orbits every 130 days Detected by Kepler using transit method

29 The Con More radiation Life has to evolve to deal with this

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31 Just the Beginning Reaching the point where we’re just starting to be able to detect Earth-sized planets. Starting to see Earth Lookalikes such as Kepler 186f Habitable planets around M-type stars

32 Easier to Detect Doppler Variations K ~ M*^(-3/2) Transit Depth ~ M^-2 M type stars ~ ¼ as massive as our sun -> Variations ~ 10 * larger

33 Planets are Everywhere We’ve seen planets around many types of stars. In Binary Systems In Star Clusters For every star in the Milky Way, there is an estimated 1.6 planets. Countless Galaxies and Stars in this Universe The odds are that Earth 2.0 is out there somewhere All we need to do is look for it

34 References 1.Deep Astronomy. “Kepler’s New Universe.” Youtube. 19 th February, 2014. 24 th April 2014, https://www.youtube.com/watch?v=YmB-MYH3_1Q&feature=player_detailpage#t=18. https://www.youtube.com/watch?v=YmB-MYH3_1Q&feature=player_detailpage#t=18 2.Gannon, Megan. “Water Found in Atmosphere of Nearby Alien Planet.” Discovery. Discovery Communication, LLC. 26 th February 2014. 26 th April 2014. http://news.discovery.com/space/alien-life-exoplanets/water-found-in-atmosphere-of- nearby-alien-planet-140226.htm. http://news.discovery.com/space/alien-life-exoplanets/water-found-in-atmosphere-of- nearby-alien-planet-140226.htm 3.“Gas Giant.” Wikipedia. Wikimedia Foundation Inc. 24 th April 2014. 1 st May 2014. http://en.wikipedia.org/wiki/Gas_giant#Extrasolar_gas_giants. http://en.wikipedia.org/wiki/Gas_giant#Extrasolar_gas_giants 4.Gens, Henry. “Professor Discovers New Exoplanet.” The Observer. The Observer. 28 th April, 2014. 1 st May, 2014. http://ndsmcobserver.com/2014/04/professor-discovers-new- exoplanet/.http://ndsmcobserver.com/2014/04/professor-discovers-new- exoplanet/ 5.“Gravitational Microlensing.” Wikipedia. Wikimedia Foundation Inc. 1 st April 2014. 17 th May 2014. http://en.wikipedia.org/wiki/Gravitational_microlensing.http://en.wikipedia.org/wiki/Gravitational_microlensing 6.Johnson, John. “International Year of Astronomy Invited Review on Exoplanets.” Caltech. 17 th March, 2009. 7.Kane, Stephen. “Kepler 186 System” Habitable Zone Gallery. 25 th April 2014, http://physics.sfsu.edu/~skane/hzgallery/493_2.png. http://physics.sfsu.edu/~skane/hzgallery/493_2.png

35 8.“Kepler 186f.” Jet Propulsion Laboratory. NASA. 23 rd April 2014, http://planetquest.jpl.nasa.gov/exoplanet/1789. http://planetquest.jpl.nasa.gov/exoplanet/1789 9.“Methods.” Jet Propulsion Laboratory. NASA. 23 rd April 2014, http://planetquest.jpl.nasa.gov/page/methods. http://planetquest.jpl.nasa.gov/page/methods 10.O’neill, Ian. “Rare Exoplanet Found in Cluster, Orbits Sun’s Twin.” Discovery. Discovery Communication, LLC. 15 th January 2014. 26 th April 2014. http://news.discovery.com/space/alien-life-exoplanets/rare-exoplanet-found- in-star-cluster-orbits-suns-twin-140115.htm. http://news.discovery.com/space/alien-life-exoplanets/rare-exoplanet-found- in-star-cluster-orbits-suns-twin-140115.htm 11.O’neill, Ian. “Weird Small ‘Puffed-Up’ Exoplanet Discovered.” Discovery. Discovery Communication, LLC. 6 th January 2014. 26 th April 2014. http://news.discovery.com/space/alien-life-exoplanets/weird-puffed-up-earth- mass-exoplanet-discovered-140106.htm. http://news.discovery.com/space/alien-life-exoplanets/weird-puffed-up-earth- mass-exoplanet-discovered-140106.htm 12.Pheonixpics. “Exoplanets – What’s All the Fuss About.” Cumbrian Sky. WordPress. 29 th March, 2009. http://cumbriansky.wordpress.com/2009/03/29/exploanets- whats-all-the-fuss-about/.http://cumbriansky.wordpress.com/2009/03/29/exploanets- whats-all-the-fuss-about/ 13.“Planet Counts.” NASA Exoplanet Archive. NASA. 24 th April, 2014. http://exoplanetarchive.ipac.caltech.edu/docs/counts_detail.html. http://exoplanetarchive.ipac.caltech.edu/docs/counts_detail.html 14.Sackett, Penny. “Microlensing Exoplanets.” Scholarpedia. 2010. 17 th May, 2014. http://www.scholarpedia.org/article/Microlensing_exoplanets. http://www.scholarpedia.org/article/Microlensing_exoplanets 15.“Super Earth.” Wikipedia. Wikimedia Foundation Inc. 22 nd April 2014. 1 st May 2014. http://en.wikipedia.org/wiki/Super-Earth.http://en.wikipedia.org/wiki/Super-Earth 16.“Terrestrial Planet.” Wikipedia. Wikimedia Foundation Inc. 21 st March 2014. 1 st May 2014. http://en.wikipedia.org/wiki/Terrestrial_planet.http://en.wikipedia.org/wiki/Terrestrial_planet


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