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Exploring Exoplanets: The Quest for Earth's Twin

Dive into the fascinating world of exoplanets, planets beyond our solar system, and the search for habitable worlds similar to Earth. Discover the various types of exoplanets, detection methods like Doppler Shift and Transit, and the Kepler space telescope's role in finding these distant worlds. Explore intriguing exoplanets like Tau Bootis b, KOI-314c, Messier 67, and Kepler-186f. Learn about the challenges of detecting Earth-sized planets and the potential for finding life beyond our solar system. Join the quest for Earth 2.0 and unravel the mysteries of the universe!

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Exploring Exoplanets: The Quest for Earth's Twin

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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

  5. 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

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

  7. 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

  8. 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

  9. 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

  10. 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

  11. Methods of Detection • Doppler Effect • Transit • Gravitational Microlensing • Many others to a lesser extent

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. Interesting Exoplanets • Tau Bootis b • KOI-314c • Messier 67 • Kepler 186 f

  18. 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

  19. 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

  20. 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

  21. 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

  22. The Con • More radiation • Life has to evolve to deal with this

  23. 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

  24. 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

  25. 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

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

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

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