ET, phone home The Good News Are we alone in the universe?
• We’ve found a lot of places to go • Probably even life out there….
Peter Watson Peter Watson
The Bad news The Really Bad news
• We can’t get there • We had better fix things here…
Peter Watson Peter Watson
The Really, Really Bad news HL Tauri from ALMA
• We may not have long enough
Image Credit: ALMA (ESO/NAOJ/NRAO), NSF Star has just got going: we can see the disc of hot gas forming planets PW Peter Watson An (almost) new-born star: Now we are seeing lots of β-Pictoris other solar systems
• still surrounded by Like this! (except this is our dust sun and Venus, June 5) • But it’s had time to form at least one giant planet • so are planets common?
Picture by Etienne Rollin
Peter Watson Peter Watson
Kepler How many? • observed 150000 stars every 30 mins. • 6 planets known since pre-history • Uranus: 1781
Vega • Neptune: 1846 • Pluto: 1931 Deneb
• Note 0.1 % change • 4 hours Note: even this is an underestimate: • symmetrical shape Kepler has 2321 candidates, 61 74 confirmed
Peter Watson
21/10/2019 •Orbit has to be aligned with earth •Need to see several transits
•Does best with large planets, close to star
•“hot Jupiters” • https://apod.nasa.gov/apod/ap151205.html
Peter Watson Peter Watson •Kepler 22b: first earth-sized planet in Kepler 11 has at least 6 Goldilocks zone (not too hot, not to cold!) planets
Peter Watson Peter Watson
Not really So planetary systems are common: do they look like ours? • Lot of stars have hot Jupiters • Some don’t know they should be in circular orbits! • HD80606b goes from 500°C to 1200°C in 6 hours • Lots go backwards
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•Planets in orbit round binary (double-star) systems: Kepler 16b
•CoRoT-7b •mass ~ five Earth, radius~ 1.7 Earth
•year lasts ~20 hours
•FAR too hot (1500°) Peter Watson Peter Watson Kepler 36
• ~Earth sized planet + Credit: Harvard-Smithsonian Center for Astrophysics/David Aguilar ~Neptune sized planet • Every 97 days approach to ~1.5 million km
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Kepler-47 On the other hand ...
• First Binary Star 2-Planet System • Maybe we need a planet called Vulcan. • Star Trek puts it round the star 40-Eridani: quite sensible • Green ring is “habitable zone”
Peter Watson Peter Watson
Peter Watson Peter Watson Water planet: K2-18B And now.. (Feb 2017) • TRAPPIST-1 system Transiting Planets and Planetesimals Small Telescope
Peter Watson Peter Watson
• 7 planets, all within orbit of Mercury And now.. • Several in Goldilocks zone • Like this! • Star is cool red dwarf • Not what we would expect for life support
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Conclusions • There may be many planets that don’t orbit stars • Seems likely ALL stars have planets • A real αστήρ πλανήτης (astēr planētēs), • We haven’t had time to observe orbits of meaning "wandering star" longer than a year or so • Except we have defined planets to be in • Maybe more than 100 billion planets in the orbit round stars! Milky Way • Many similar to Earth So let’s go
Peter Watson Peter Watson So what does this do for The Wow signal alien life? • 1977 from Big Ear observatory (Ohio) •Where are they? • Very big signal, never repeated • Before GUI’s!
Peter Watson Peter Watson
Search for Extraterrestrial Intelligence A depressing corollary • Vast amounts of data from Arecibo are never analysed
• If aliens are smart enough to communicate over large • Fermi’s question: where are they? distances AND too dumb to use cable, we could pick up their signals • if the universe is full of planets (it is) and some have liquid water (almost certainly) and
evolution is universal (why wouldn’t it be?)….. • Why isn’t the galaxy full of inhabited planets with intelligent species who want to talk to us?
Peter Watson
The Drake Equation • prob. that intelligent life can communicate across space =5% • How many advanced civilizations are there in our • lifetime of intelligent civilization =3500 yrs galaxy (50 billion stars)? • # of times a civilization could re-develop =1 • # of new stars born each year = 10 • Total number of civilizations in our galaxy at the • fraction of stars with planets = 100% moment?
• # of habitable planets/system = 0.5 • http://www.as.utexas.edu/astronomy/education/drake/drake.html-old • probability that life evolves =100% 42!!!!!!!!!!!! • prob. that life develops intelligence =5% • •Well, you decide which number I got wrong!
Peter Watson Peter Watson •No evidence that Nature is working towards more complex and intelligent beings
An image that •Steven Jay Gould has pointed out that this is probably temporary: viruses have much is embedded better survival values than humans in our sub- conscious
• Note whole orders of living beings Maybe intelligence isn’t have disappeared from the earth • this is Orthrozanclus for no apparent reason. such a great idea! • E.g Burgess shale •
Hiroshima Hiroshima Aug 5 1945 Aug 6 1945
•this is Opabinia
• Maybe intelligent species last a really short time
In summary:
• There are lots of planets • No known or foreseeable technology will get us to a extra-solar planet • Total absence of any evidence for extra-terrestrial life suggest it is very uncommon: pick your own reason why • If you want to play your own games with the data, go to http://exoplanet.eu