OLLI SC211 SPACE EXPLORATION: THE SEARCH FOR LIFE BEYOND EARTH April 13, 2017 Michal Peri NASA Solar System Ambassador Exoplanet2 Detection • Methods • Missions • Discoveries • Resources Image: C. Pulliam & D. Aguilar/CfA A long history … in our imaginations 3 https://en.wikipedia.org/wiki/Giordano_Bruno#/media/File:Relief_Bruno_Campo_dei_Fiori_n1.jpg 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. 3 https://www.loc.gov/today/cyberlc/feature_wdesc.php?rec=7148 5 Detection Methods Radial Velocity 619 planets Gravitational Microlensing 44 planets Direct Imaging 44 planets Transit 2771 planets Velocity generates Doppler 7 Shift Sound star receding star approaching Light wave “stretched” → red shift wave “squashed” → blue shift Orbiting planet causes Doppler shift in starlight 8 https://exoplanets.nasa.gov/interactable/11/ Radial Velocity Method 9 • 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 Doppler Shift Time Nikole K. Lewis, STScI Radial Velocity Detections Radial Velocity 1992 Planetary Mass 10 Detection Methods Radial Velocity 619 planets Gravitational Microlensing 44 planets Direct Imaging 44 planets Transit 2771 planets • Microlens 12 • GM rc • Background Method light – source • • 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 Gravity-warped space acts like a lens 13 https://exoplanets.nasa.gov/interactable/11/ MicrolensMicrolensing Detection 14 ~51 planets detected Brightness Mass Ratio and Angular Separation is Measured • Mass ratio of the planet to the star and the angular separation between the planet and star is measured Microlensing by Rogue Planets • “Einstein Blip” 15 short-lived brightness flare • The only way to detect dark free-floating planets • Estimate how common such “rogue” planets are in the galaxy Video: NASA Ames/JPL-Caltech/T. Pyle Detection Methods Radial Velocity 619 planets Gravitational Microlensing 44 planets Direct Imaging 44 planets Transit 2771 planets Direct Imaging Method 17 • 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 HR 8799 System Marois et al. (2010) 18 Detection Methods Radial Velocity 619 planets Gravitational Microlensing 44 planets Direct Imaging 44 planets Transit 2771 planets Transit Method • Brightness drops as the 20 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 Planetary Radius Planetary 22 Image Credit: NASA Nikole K. Lewis, STScI What we can learn from transits 23 3,472 Exoplanets Discovered! 24 ♢ Radial Velocity ♢ Microlensing ♢ Direct Imaging ♢ Transit S. Rinehart, NASA Goddard Exoplanet25 Detection • Methods • Missions • Discoveries • Resources Image: C. Pulliam & D. Aguilar/CfA 26 S. Rinehart, NASA Goddard Kepler 27 2009-2013 Nikole K. Lewis, STScI Kepler’s Second Light: K2 28 2009-201 W Stenzel, Nasa Ames Kepler vs. TESS 29 • Kepler: Census of the Statistics of Exoplanets – to Estimate Nplanets • TESS: Open the Door for Characterizing Exoplanets S. Rinehart, NASA Goddard 30 Survey MethodologySurvey Design TESS 200 ly radius TESS – Launch 2018 31 https://youtu.be/FlJyuDQOeoo Anticipated TESS Discoveries 32 Sullivan, et al. 2015 TESS: Anticipated Discoveries More than 500 Small Exoplanets! 33 Sullivan, et al. 2015 One Parameter is Not Enough Seager Hydrogen Jupiter 10.0 Water 2007 al.et Rock (MgSiO3) Iron h t r a e R / 1.0 R Earth Our Solar System Venus Super-Earths A few other exoplanets 0.1 0.1 1.0 10 100 1000 M/Mearth Wanted: Bright Stars +4 TESS, Bright Stars Kepler, Faint Stars Naked-Eye e d u t i n +8 g Binoculars a M r Telescope a t S 100 x +12 Brighter t s o H +16 1 10 S. Rinehart Planet Radius (RE) NASA Goddard James Webb Space Telescope Launch: October 2018 36 Video: NASA/Northrop Grumman Ground-Based Telescopes 37 The Ultimate Goal 38 Future Large Space Missions… HDST ATLAST Concept HDST Drawing LUVOIR HabEx 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) 39 Pueyo, N’Diayeikole, STScI Exoplanet40 Discoveries Image: C. Pulliam & D. Aguilar/CfA First Confirmed Detection • (1992) Wolszczan and Frail 41 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 42 • “Hot Jupiter” Mass = .47 x MJupiter period = 4.23 days orbiting at 0.05AU • Migration theory of planetary formation • Water molecules detected in planetary atmosphere spectra (January 2017) NASA/JPL-Caltech/T. Pyle (SSC) Earth-Like Planets 43 NASA Ames/W. Stenzel Goldilocks Planets in the Habitable Zone 44 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 NASA Ames/W. Stenzel Petigura/UC Berkeley, Howard/UH-Manoa, Marcy/UC Berkeley A Planet Orbiting Proxima Centauri Our Nearest Stellar Neighbor 45 ESO/M. Kornmesser 7 Potentially Habitable Planets Around a Nearby Star: Trappist-1 46 Great! When can I visit? 47 Breakthrough Starshot • Earth-based array of lasers 48 (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 Exoplanet49 Resources Online Image: C. Pulliam & D. Aguilar/CfA NASA Eyes on Exoplanets App 50 Video tutorial: https://exoplanets.nasa.gov/resources/1051/ 51 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 This product is based upon work supported by NASA. Any opinions, 53findings, 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 The Drake Equation N 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. Modified 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. 56 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 Spitzer 58 Credit: NASA/JPL-Caltech WFIRST – 2020s? 59 Credit: M. Credit: Penny Penny Orbit Size in AU S. Rinehart, NASA Goddard GiantLife As Ground We DON’T-Based Telescopes Know It MIT60 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.” Carl Tate, Space.com 61 https://exoplanets.nasa.gov/interactable/11/ Pulliam & (CfA) Pulliam Aguilar 62Exploring the DIVERSITY of Worlds .