Earth 2.0: NASA's Search for Earth-size Planets Daniel Dale Physics & Astronomy University of Wyoming
Image credit: NASA Outline
The Kepler mission Target Technique Results
Outline
The Kepler mission Target Technique Results
1571-1630
What fraction of stars in our galaxy harbor potentially habitable, Earth-size planets?
The “habitable zone”
Image: NASA The “habitable zone”
Image: NASA The Drake Equation N = R* · f · n · f · f · f · L p e l i c
Where: • N = # civilizations in Galaxy w/detectable electromagnetic emissions • R* = Rate of star formation suitable for the development of intelligent life • fp = Fraction of those stars with planetary systems • ne = Number of planets, per solar system, with environment suitable for life • fl = Fraction of suitable planets on which life actually appears • fi = Fraction of life-bearing planets on which intelligent life emerges • fc = Fraction of civilizations that develop a technology that releases detectable signs of their existence into space • L = Length of time such civilizations release detectable signals into space
Kepler launch 06 March 2009
Cape Canaveral Delta II rocket 0.95 m mirror
Outline
The Kepler mission Target Technique Results
Where does Kepler search?
Image: NASA Where does Kepler search?
Where does Kepler search?
Image: NASA Outline
The Kepler mission Target Technique Results
Exoplanet Detection Methods
Radial velocity Pulsar timing Direct imaging Gravitational microlensing Transit Polarimetry Astrometry
Exoplanet Detection Methods
Radial velocity
Image: European Southern Observatory Exoplanet Detection Methods
Radial velocity
Preferentially detects large, close-in planets
Only provides lower limit to mass
Image: European Southern Observatory Exoplanet Detection Methods
Pulsar timing quite rare & inhospitable 1991 blooper
Images: Alex Wolszczan (Penn St.) Exoplanet Detection Methods
Direct imaging
Prefers infrared- bright planets far from faint stars
Image: European Southern Observatory Exoplanet Detection Methods
Gravitational microlensing
Best for orbits that are 1-10 AU Not repeatable
Image: Malyszkz How does Kepler search? Transit photometry
150,000 stars observed Planets may occult their parent star
Image: NASA The first recorded transit of Venus
Image credit: Ford Madox Brown, mural at Manchester Town Hall
How does Kepler search? Transit photometry
Kepler provides planetary “candidates” Ideally confirmed by another technique
10% false positives: Tightly bound or dim binary star companion Stellar pulsations Periodic instrumental glitches
Image: NASA
Exoplanet Detection Methods
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Image: wikipedia Year
Image credit: NASA Outline
The Kepler mission Target Technique Results
Transiting planets pre-Kepler h t r a E o t e v i t a l e R e z i S
Image: NASA Orbital period (days) Candidates as of June 2010
Jun 2010 h t r a E o t e v i t a l e R e z i S
29 29 Image: NASA Orbital period (days) Candidates as of Feb 2011 Jun 2010 Feb 2011 h t r a E o t e v i t a l e R e z i S
30 Image: NASA Orbital period (days) Candidates as of Dec 2011 Jun 2010 Feb 2011 Dec 2011 h t r a E o t e v i t a l e R e z i S
31 Image: NASA Orbital period (days) Candidates as of Jan 2014 h t r a E
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Image: NASA Orbital period (days)
Image credit: NASA/W Stenzel Kepler's habitable zone planets
Kepler 62 system
Image credit: NASA Ames/JPL-Caltech Kepler's smallest habitable zone planet
Kepler 62f 1200 lyr away (Lyra) 40% larger than Earth 267 day orbit
Image credit: NASA Ames/JPL-Caltech/Tim Pyle 22% of Sun-like stars harbor Earth-size planets orbiting in their habitable zones (Petigura et al. 2013)
Image: NASA Extrapolate the result to the entire Milky Way: 40 billion habitable Earth-size planets (Petigura et al. 2013)
Image: NASA Transit and Doppler Measurements Yield Density
+ 10b Size
Density
Mass = 8.8 g/cm3 Volume Image: NASA
Image: NASA The Drake Equation N = R* · f · n · f · f · f · L p e l i c
Where: • N = # civilizations in Galaxy w/detectable electromagnetic emissions • R* = Rate of star formation suitable for the development of intelligent life • fp = Fraction of those stars with planetary systems • ne = Number of planets, per solar system, with environment suitable for life • fl = Fraction of suitable planets on which life actually appears • fi = Fraction of life-bearing planets on which intelligent life emerges • fc = Fraction of civilizations that develop a technology that releases detectable signs of their existence into space • L = Length of time such civilizations release detectable signals into space
The Drake Equation N ~ 10 · 1 · 0.2 · ? · ? · ? · ?
Where: • N = # civilizations in Galaxy w/detectable electromagnetic emissions • R* = Rate of star formation suitable for the development of intelligent life • fp = Fraction of those stars with planetary systems • ne = Number of planets, per solar system, with environment suitable for life • fl = Fraction of suitable planets on which life actually appears • fi = Fraction of life-bearing planets on which intelligent life emerges • fc = Fraction of civilizations that develop a technology that releases detectable signs of their existence into space • L = Length of time such civilizations release detectable signals into space
The Drake Equation
Progressing from left to right, the equation is increasingly uncertain.
Many consider this equation to simply be conceptual, something to start a conversation on how to approach a search for life.
Fermi Paradox: Where are they?
Kepler Exoplanets By the Numbers
Candidates: 4234 July 2014 (3845 April 2014)
Confirmed: 978 July 2014 (961 April 2014)
Estimated Galaxy Total: 40 billion
22% of Sun-like stars harbor Earth-size, habitable planets
Nearest: Alpha Centauri Bb at 4 lyr
Least massive: 2 lunar masses
Most massive: 29 Jupiter masses
Orbital periods: few hours to thousands of years
Thank You
Kepler's Future Kepler experienced 2 reaction wheel failures (July '12; May '13)
No longer can point with the requisite accuracy
It is now carrying out its “K2” mission
Relies on pressure from sunlight to serve as the “third wheel” and to balance the 'scope
Image credit: NASA/W. Stenzel