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Earth 2.0: NASA's Search for Earth-size Planetsphysics.uwyo.edu/~aschwortz/LASSI/files/DDale.pdf ·...
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Earth 2.0: NASA's Search for Earth-size Planets Daniel Dale Physics & Astronomy University of Wyoming Image credit: NASA
Transcript of Earth 2.0: NASA's Search for Earth-size Planetsphysics.uwyo.edu/~aschwortz/LASSI/files/DDale.pdf ·...
Earth 2.0: NASA's Search for Earth-size Planets
Daniel DalePhysics & AstronomyUniversity of Wyoming
Image credit: NASA
Outline
The Kepler missionTargetTechniqueResults
Outline
The Kepler missionTargetTechniqueResults
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 EquationN = R* · f
p · n
e · f
l · f
i · f
c · L
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 launch06 March 2009
Cape CanaveralDelta II rocket0.95 m mirror
Outline
The Kepler missionTargetTechniqueResults
Where does Kepler search?
Image: NASA
Where does Kepler search?
Where does Kepler search?
Image: NASA
Outline
The Kepler missionTargetTechniqueResults
Exoplanet Detection Methods
Radial velocityPulsar timingDirect imagingGravitational microlensingTransitPolarimetryAstrometry
Exoplanet Detection Methods
Radial velocity
Image: European Southern Observatory
Exoplanet Detection Methods
Radial velocity
Preferentially detectslarge, close-in planets
Only provides lowerlimit to mass
Image: European Southern Observatory
Exoplanet Detection Methods
Pulsar timingquite rare & inhospitable1991 blooper
Images: Alex Wolszczan (Penn St.)
Exoplanet Detection Methods
Direct imaging
Prefers infrared-bright planetsfar from faint stars
Image: European Southern Observatory
Exoplanet Detection Methods
Gravitational microlensing
Best for orbits that are 1-10 AUNot repeatable
Image: Malyszkz
How does Kepler search?Transit photometry
Image: NASA
150,000 stars observedPlanets may occult their parent star
The first recorded transit of Venus
Image credit: Ford Madox Brown, mural at Manchester Town Hall
How does Kepler search?Transit photometry
Image: NASA
Kepler provides planetary “candidates”Ideally confirmed by another technique
10% false positives:Tightly bound or dim binary star companionStellar pulsationsPeriodic instrumental glitches
Exoplanet Detection Methods
Year
# D
etec
ted
Image: wikipedia
Image credit: NASA
Outline
The Kepler missionTargetTechniqueResults
Transiting planets pre-KeplerS
ize
Re
lati
ve
to
Ea
rth
Orbital period (days)Image: NASA
2929
Candidates as of June 2010
Jun 2010
Orbital period (days)
Siz
e R
ela
tiv
e t
o E
art
h
Image: NASA
30
Candidates as of Feb 2011Jun 2010 Feb 2011
Siz
e R
ela
tive
to
Ea
rth
Orbital period (days)Image: NASA
31
Candidates as of Dec 2011Jun 2010 Feb 2011 Dec 2011
Siz
e R
ela
tive
to
Ea
rth
Orbital period (days)Image: NASA
Candidates as of Jan 2014S
ize
Rel
ati
ve
to E
art
h
Orbital period (days)Image: NASA
Image credit: NASA/W Stenzel
Kepler's habitable zone planets
Kepler 62system
Image credit: NASA Ames/JPL-Caltech
Kepler's smallest habitable zone planet
Image credit: NASA Ames/JPL-Caltech/Tim Pyle
Kepler 62f1200 lyr away (Lyra)40% larger than Earth267 day orbit
22% of Sun-like stars harborEarth-size planets orbitingin 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 DopplerMeasurements Yield Density
+10b Size
MassVolume
= 8.8 g/cm3
Density
Image: NASA
Image: NASA
The Drake EquationN = R* · f
p · n
e · f
l · f
i · f
c · L
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 EquationN ~ 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 NumbersCandidates: 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 FutureKepler 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
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