olli sc211 space exploration: the search … sc211 space exploration: the search for life beyond...
TRANSCRIPT
OLLI SC211
SPACE EXPLORATION: THE SEARCH FOR LIFE
BEYOND EARTH April 13, 2017
Michal Peri NASA Solar System Ambassador
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Image: C. Pulliam & D. Aguilar/CfA
Exoplanet Detection
• Methods
• Missions
• Discoveries
• Resources
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A long history … in our imaginations
Giordano Bruno in his De l'infinito universo et mondi (1584) suggested that "stars are other suns with their own planets” that “have no less virtue nor a nature different to that of our earth" and, like Earth, "contain animals and inhabitants.” For this heresy, he was burned by the inquisition.
https://en.wikipedia.org/wiki/Giordano_Bruno#/media/File:Relief_Bruno_Campo_dei_Fiori_n1.jpg
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https://www.loc.gov/today/cyberlc/feature_wdesc.php?rec=7148
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Detection Methods
Radial Velocity 619 planets
Gravitational Microlensing 44 planets
Direct Imaging 44 planets
Transit 2771 planets
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Velocity generates Doppler Shift
star receding star approaching
Sound
Light
wave “stretched” → red shift wave “squashed” → blue shift
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Orbiting planet causes Doppler shift in starlight
https://exoplanets.nasa.gov/interactable/11/
Radial Velocity Method
• The most successful method of detecting exoplanets pre-2010
• Doppler shifts in the stellar spectrum reveal presence of planetary companion(s)
• Measure lower limit of the planetary mass and orbital parameters
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Nikole K. Lewis, STScI Time
Do
pp
ler
Shif
t
Radial Velocity Detections 10
Pla
net
ary
Mas
s
1992
Detection Methods
Radial Velocity 619 planets
Gravitational Microlensing 44 planets
Direct Imaging 44 planets
Transit 2771 planets
Microlens Method
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•
• GM rc•
–
•
•
•
–
•
• Planet’s gravity acts like a lens
• Focuses light from background source
• Can detect planets that are invisible to other methods
https://wfirst.gsfc.nasa.gov/exoplanets_microlensing.html
Background
light
source
Gravity-warped space acts like a lens
https://exoplanets.nasa.gov/interactable/11/
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Mass Ratio and Angular Separation is Measured
Microlens Detection 14
Microlensing
• Mass ratio of the planet to the star and the angular
separation between the planet and star is measured
~51 planets detected
Brig
htn
ess
15 • “Einstein Blip” short-lived brightness flare
• The only way to detect dark free-floating planets
• Estimate how common such “rogue” planets are in the galaxy
Microlensing by Rogue Planets
Video: NASA Ames/JPL-Caltech/T. Pyle
Detection Methods
Radial Velocity 619 planets
Gravitational Microlensing 44 planets
Direct Imaging 44 planets
Transit 2771 planets
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Direct Imaging Method
• Create “artificial” eclipse to block stellar glare
• Enable planet(s) to be imaged directly
• Method first developed to observe solar corona, hence “coronagraphy”
Image: UCAR/NCAR/HAO
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HR
87
99
System M
arois et al. (2
01
0)
Detection Methods
Radial Velocity 619 planets
Gravitational Microlensing 44 planets
Direct Imaging 44 planets
Transit 2771 planets
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Transit Method
• Brightness drops as the planet occult a small fraction of the stellar disk
• Requires alignment of planet’s orbit with the line of sight to earth
• Currently the only way to directly measure planetary radius
Nikole K. Lewis, STScI
Transit Detections 21
Pla
net
ary
Rad
ius
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Image Credit: NASA Nikole K. Lewis, STScI
What we can learn from transits
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3,472 Exoplanets Discovered!
S. Rinehart, NASA Goddard
♢ Radial Velocity
♢ Microlensing
♢ Direct Imaging
♢ Transit
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Image: C. Pulliam & D. Aguilar/CfA
Exoplanet Detection
• Methods
• Missions
• Discoveries
• Resources
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S. Rinehart, NASA Goddard
Kepler 27
2009-2013 Nikole K. Lewis, STScI
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Kepler’s Second Light: K2
2009-201 W Stenzel, Nasa Ames
• Kepler: Census of the Statistics of Exoplanets – to Estimate Nplanets
• TESS: Open the Door for Characterizing Exoplanets
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Kepler vs. TESS
S. Rinehart, NASA Goddard
Survey Methodology 30 Survey
Design TESS
200 ly radius
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Anticipated TESS Discoveries
Sullivan, et al. 2015
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Sullivan, et al. 2015
More than 500 Small Exoplanets!
TESS: Anticipated Discoveries
Hydrogen
Water
Rock (MgSiO3)
Iron
Our Solar System
Super-Earths
A few other exoplanets
10.0
1.0
0.10.1 1.0 10 100 1000
R/R
eart
h
M/Mearth
Jupiter
Earth
Venus
One Parameter is Not Enough Seager et al. 2
00
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Wanted: Bright Stars
100xBrighter
HostStarM
agnitude
PlanetRadius(RE)1 10
+4
+16
+8
+12
TESS,BrightStarsKepler,FaintStars
Naked-Eye
Binoculars
Telescope
S. Rinehart
NASA Goddard
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James Webb Space Telescope Launch: October 2018
Video: NASA/Northrop Grumman
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Ground-Based Telescopes
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The Ultimate Goal
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A simulated image showing how a solar-like
system 45 light years away might appear to
a coronagraph on the proposed 12m
High Definition Space Telescope (HDST)
ATLAST
HDST
LUVOIR
HabEx
HDST
Concept
Drawing
Future Large Space Missions…
Pueyo, N’Diayeikole, STScI
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Image: C. Pulliam & D. Aguilar/CfA
Exoplanet
Discoveries
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First Confirmed Detection
• (1992) Wolszczan and Frail discovered two planets orbiting millisecond pulsar PSR 1257+12
• A third, smaller planet was discovered 1994
• Pulsar planets are RARE and inhospitable to life
NASA/JPL-Caltech/R. Hurt (SSC)
First Planet found around a Sun-Like Star • (1995) Pegasus 51b • “Hot Jupiter”
Mass = .47 x MJupiter period = 4.23 days orbiting at 0.05AU
• Migration theory of planetary formation
NASA/JPL-Caltech/T. Pyle (SSC)
• Water molecules detected in planetary atmosphere spectra (January 2017)
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Earth-Like Planets
NASA Ames/W. Stenzel
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Goldilocks Planets in the Habitable Zone
NASA Ames/W. Stenzel
Conditions for Life
• The right kind of star – stable and long-lived
• The right orbital distance and temperature for liquid water
• A solid rocky surface where water can pool
Petigura/UC Berkeley, Howard/UH-Manoa, Marcy/UC Berkeley
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A Planet Orbiting Proxima Centauri Our Nearest Stellar Neighbor
ESO/M. Kornmesser
7 Potentially Habitable Planets Around a Nearby Star: Trappist-1
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Great! When can I visit? 47
Breakthrough Starshot 48 • Earth-based array of lasers
(or maybe microwave transmitters) accelerates ultra-light space sail to a significant fraction of the speed of light
• Gram-scale instrument-on-a-chip payload
• Inexpensive mass-produced probes, launched 1000s at a time
• Could reach Proxima b in 20 (or maybe 50) years, or Trappist-1 in a few hundred years
Image: Breakthrough Initiatives
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Image: C. Pulliam & D. Aguilar/CfA
Exoplanet
Resources
Online
NASA Eyes on Exoplanets App
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Video tutorial: https://exoplanets.nasa.gov/resources/1051/
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SC211: Exploring Our Universe Thursday April 13, 10:00-12:00, The Search for Life Beyond Earth Michal Peri, NASA Solar System Ambassador Thursday April 20, 10:00-12:00, Gravity Waves Geoffrey Lovelace , Gravity Waves Investigator, CSUF Thursday April 27, 1:00-3:00, James Webb Space Telescope Jon Arenberg , Chief Engineer, James Webb Telescope, Northrup
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This product is based upon work supported by NASA. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Aeronautics and Space Administration
Image: C. Pulliam & D. Aguilar/CfA
N = The number of civilizations in the Milky Way Galaxy whose electromagnetic emissions are detectable. R* = The rate of formation of stars suitable for the development of intelligent life. fp = The fraction of those stars with planetary systems. ne = The number of planets, per solar system, with an environment suitable for life. fl = The fraction of suitable planets on which life actually appears. fi = The fraction of life bearing planets on which intelligent life emerges. fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space. L = The length of time such civilizations continue to release detectable signals into space.
The Drake Equation
N
N = The number biosystems with life as we know it. R* = The rate of formation of stars suitable for the development of intelligent life. fp = The fraction of those stars with planetary systems. ne = The number of planets, per solar system, with an environment suitable for life. fl = The fraction of suitable planets on which life actually appears. fi = The fraction of life bearing planets on which intelligent life emerges. fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space. L = The length of time such life continues to exist.
Modified Drake Equation
N
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But seriously, there’s loads of intelligent life. It’s just not screaming constantly in all directions on the handful of frequencies we search.
List of Exoplanet Searches
1 Ground-based search projects 48(!) listed on Wikipedia 2 Space missions
2.1 Past and current Hubble, Spitzer, MOST, EPOXI, SWEEPS, COROT, Kepler, K2, Gaia 2.2 Planned CHEOPS (2018), TESS (2018), JWST (2018), PLATO (2025), WFIRST (mid-2020’s) 2.3 Proposed ATLAST, HDST, EXCEDE FINESSE, PEGASE New Worlds Mission
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Spitzer
Credit: NASA/JPL-Caltech
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Cred
it: M. Pen
ny
WFIRST – 2020s?
S. Rinehart, NASA Goddard
Orbit Size in AU
Giant Ground-Based Telescopes
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Carl Tate, Space.com
Life As We DON’T Know It MIT physics professor Sara Seager modeled chemical combinations that could signal the presence of alien life. She and her biochemistry colleagues computer-generated virtual combinations of the six main elements associated with life on Earth: carbon, nitrogen, oxygen, phosphorous, sulfur and hydrogen. It is still unknown which of the recipes are biologically useful.
These compounds are not found on Earth, but astronomers can look for them in exoplanetary atmospheres. “Why not consider all potential molecules that could be in gas form,” Seager said recently. “I just combine them in any way possible, like just taking letters in the alphabet and combining them in all ways.”
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Pu
lliam &
Agu
ilar (CfA
)
Exploring the DIVERSITY of Worlds