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The Next 25(?) Years Future Missions to Search for Extra-solar Planets and Life The census so far As of December 3rd: 268 extrasolar planets Almost exclusively “Hot Jupiters” in elliptical orbits: only 3 with the possibility of a habitable terrestrial planet So far, no extrasolar Earths... but we haven't really looked We can see this! that hard But we want this! Limited by search size... Imagine, if you shrunk our solar system to a little larger than a quarter: Our whole Solar System Our Milky Way Galaxy would be this big would be the size of the United States. From: http://planetquest.jpl.nasa.gov/Navigator/material/sim_material.cfm And the neighborhood where we’ve found new planets would only be the size of Manhattan. You can even see some of the stars that have planets in the night sky… From: …if you know where to look From: Limited by ground-based technique... Doppler “wobble” is limited by our spectral resolution (we can already see shifts of only ~100 mph) Earth's atmosphere causes stars to “twinkle” when viewed from the ground, so this limits imaging methods The Goal: To find planets capable of supporting life or even find extra-solar life! Recap: We need... Larger search area New technique to find terrestrial planets in the habitable zone of their stars! It’s all about location, location, location! A New Technique... The ultimate goal is to directly image an extrasolar Earth But right now we're pretty far from that. Prof. Close's work: A New Technique... The ultimate goal is to directly image an extrasolar Earth But right now we're pretty far from that. But we can (just) image super Jupiters New results (1 year old) from Keck & Gemini telescopes The Next Step Kepler (NASA) COROT (ESA) Kepler: A Larger Search Area Kepler Field of View 100,000 stars! Sensitive to extrasolar “Earths” around stars like our Sun 3000 light-years away 2/3 of systems surveyed will be binaries... A New Technique Transits (from space) Earth would lower the Sun's brightness by only 1/10,000 for up to 13 hours. We're limited by: Orientation The intrinsic variability of stars Orientation Planet Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Orbit (AU) 0.39 0.72 1 1.52 5.2 9.5 19.2 30.1 Transit Depth (%) Probability (%) 0.0012 1.19 0.0076 0.65 0.0084 0.47 0.0024 0.31 1.01 0.089 0.75 0.049 0.135 0.024 0.127 0.015 12% of the time we detect Earth or Venus... we detect both of them. Stellar Variability • Stars vary, but on different timescales • We need to see a planet transit several times to know it's real: it will take 4 transits (years) to detect an “Earth” We will see only about 0.5%!! of Earth-like planets transit in front of their stars! Kepler specs Will look at 100,000 stars in 4 years! 95 mega pixels!! (Your digital camera has ~ 4-5 and these CCDs need to be much higher quality) Expects to find ~ 50 Earth-like planets! Obviously depends on how many Earth-like solar systems actually form, but if they are there we WILL see them! More on Kepler http://www.bridgewater.edu/~rbowman/ISAW/Transit-1.html SIM (NASA) & Darwin (ESA) 2015 ??? Space Interferometry specs Looks for planets by detecting the wobble of star due to planet, BUT by directly measuring the movement of the star as opposed to just looking at the change in the wavelength emitted by the star To detect Earth-size planets with this it needs and accuracy of 1 microarcsecond 1 * 10-6 arcseconds which is like seeing a nickel at the distance of the Moon! SIM will look at the nearest ~100 stars to look for planets of ~ few Earth masses! Terrestrial Planet Finder 2020 ??? Will find terrestrial size planets: by astrometry (detecting the wobble of the host star directly) also imaging them directly by coronagraphy (meaning blocking out the light of the central star to observe fainter objects around it) TPF will survey 250 of the closest stars as a follow up for Kepler and SIM So by sometime this century we will almost certainly have a real image of a terrestrial planet….. But if we find terrestrial planets how do we detect life? This is not as easy as it might sound…. We can look for things that are common in Earth’s atmosphere like Oxygen, Methane, CO2 But Venus, Earth and even Mars look pretty similar in a spectrum…..and yet they are very different planets After TPF? Life Finder Mission? Human manned observatory on the Moon or somewhere in space to look for signatures like chlorophyll And if we find signatures of Life Planet Imager? To get more information about a planet with life we would require a large number of telescopes working together as to give a total observing area around 350km!!