exoplanet discoveryj-pinkney/phys3471/prot3471... · • 19 exoplanets have been detected . who is...
TRANSCRIPT
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Daniel Steigerwald
EXOPLANET DISCOVERY
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WHAT IS AN EXOPLANET?
• An exoplanet is a planet outside of our solar system
• Extrastellar
• Rogue
• 1853 Planets
• 1162 planetary systems
• 473 Multiple planetary systems
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HISTORY OF EXOPLANET DISCOVERY
• Ancient Greeks speculated of other solar systems
• 1584 Giordano Bruno “countless suns and countless earths all rotating around their suns”
• In the 1960s Peter van de Kamp thought he discovered planets orbiting Bernard’s Star
• Photographic plates
• Gas giants
• Alexander Wolszczan in 1994
• Pulsar
• 1995 first planet in orbit of a sun like star (51 Pegasi)
• Radial Velocity
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DIRECT EXOPLANET DISCOVERY METHOD
• Direct Observation
• Nearly impossible to resolve reflected starlight
• Viewed by observing thermal radiation of planet
• Planets must be hot
• Accurate with radius, not mass
• First direct observation in 2004
• 2M1207 and 2M1207B
• “Very Large Telescope”
• 100 Times more faint
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VERY LARGE TELESCOPE
• Located in the desert of northern Chile
• Operated by European Southern Observatory
• Four individual Telescopes 8.2 meters across
• Visible to infrared wavelength
• Can detect objects four billion times more faint than the human eye can detect
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INDIRECT METHOD OF EXOPLANET DISCOVERY
• Changes in radial velocity
• Doppler shifts indicate movement
• This movement is caused by the gravitational pull of another planet
• Transit method
• Planet travels between star and observer
• Change in the amount of light received
• Orbital Brightness Modulus
• Similar to transit method
• More than just blocking star light
• Microlensing
• Cool!
• Uses relativity!
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RADIAL VELOCITY METHOD
• A solar system is revolves around its center of mass
• Newton’s third law
• Newton’s law of gravitation
• This will cause the star to move
• Studying the Doppler shift can detect this movement
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RADIAL VELOCITY METHOD CONTINUED
• Instrumental improvements have lead to the more planets being discovered by this
method.
• Improved CCDs
• Radial velocity measurement precision has improved from 50 m/s to 1 m/s
• Accurate readings on mass
• Cannot give measurements for radius
• The closer the mass of the planet to the star, the easier to detect.
• 𝑟1 = 𝑢/𝑚1
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RADIAL VELOCITY METHOD
• http://astro.unl.edu/naap/esp/detection.html
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TRANSIT METHOD
• Think of it as a very partial eclipse
• Impossible to notice by just looking in a telascope
• Photometry
• Measurement of the number of photons that reach the detector
• Accurate measurement of radius
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TRANSIT METHOD CONTINUED
• Major drawbacks
• Estimated that only 0.47% of planets that are 1 AU from sun will have transit that
would be detectable from Earth
• Up to 40% false positives.
• Need other methods to confirm
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TRANSIT METHOD MISSIONS
• Kepler Spacecraft
• Launched in 2009
• Confirmed 995 exoplanets, 3000+ candidates
• COROT
• COnvection ROtation and planetary Transits
• French space agency
• >30 observations
• Failed
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ORBITAL BRIGHTNESS MODULATIONS
• Hard to resolve
• Star shines on the planet
• Additional brightness
• Additional warmth
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MICROLENSING
• Distant star light bend applied to planets
• Plant works as lens bending light
• Planet doesn’t need to emit any radiation
• Can be very cold
• 19 exoplanets have been detected
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WHO IS WINNING?
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SUMMERY OF INDIRECT METHODS
• The transit method relies for the observer, the exoplanet, and the star to be on the same
plane
• Other methods don’t require a perfect plane, though it may be easier, can’t be viewed
when perpendicular
• Radial velocity
• Orbital brightness modulus
• The microlensing method only requires that a distant star at some point gets in line with
the exoplanet and the observer
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QUESTIONS?
• What method do you think will prevail as the most prolific method in the next 100 years?
• What is another astrophysics topic that can be studied through microlensing?
• What method would be employed in the search of an “Earth-like” planet?
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REFERENCES
• Images courtesy of Wikipedia
• http://www.space.com/17738-exoplanets.html
• http://planetquest.jpl.nasa.gov/page/history
• http://www.eso.org/public/teles-instr/paranal/
• http://astro.unl.edu/naap/esp/dopplereffect.html
• http://lcogt.net/spacebook/transit-method
• http://www.cfa.harvard.edu/news/su201319
• http://www.planetary.org/explore/space-topics/exoplanets/microlensing.html
• Carroll, Bradley W., and Dale A. Ostlie. An Introduction to Modern Astrophysics. San Francisco:
Pearson Addison-Wesley, 2007. Print.
• Chaisson, Eric, and S. McMillan. Astronomy Today. Boston, MA: Addison-Wesley, 2007. Print.