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Astronomy 2021A/B Lecture Notes - Exoplanet, Planetary Science, Extraterrestrial Life

Course Code
ASTR 2021A/B
Peter G Brown

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1 A Universe of Life? (page 1)
- Aliens everywhere in media movies, tabloids, even serious papers/magazines run the occasional articles on UFO sightings or “Area 51”
- Around ½ of all Americans claim to believe we have already been visited by beings from other worlds
- Scientists skeptical about aliens on Earth .: search for life in other worlds, searching for signals
- Important search to change perspective on how we fit into universe as a whole, and give deeper meaning to life here on Earth
What are we searching for?
- Extraterrestrial life (life beyond Earth) includes any sign of life simple, complex, intelligent, whatever
- Yet must define what life is in the first place, which affects how we search for life in universe complicated question
o e.g. beetle/mushroom vs clouds/fire/crystals
o how do we classify? Movement, growth, reproduction and spread? Right side does this too
o because of difficulty , for scientific search, “life” = recognizably Earth-like, can recognize based on studying Earth life
must start somewhere
Is it reasonable to imagine life beyond Earth?
- Search for life new; IDEA of life not ancient cultures e.g. ancient Greeks
- Until recently, no way to scientifically test, could only imagine
o Any small data misinterpreted too
- Venus thought paradise; mars thought canals .: martian life (none actually)
- NOW enough telescope/spacecraft photos of our solar system .: quite confident no life still looking though LOT.
- Why?
o 1) Tiny microbes might exist, even if multicellular don’t
o 2) knew stars everywhere, now know planets everywhere too .: more places to look
o 3) enough knowledge/tech to go about it scientific method
Know conditions life exist
Can’t look yet, but spacecraft improving and telescope for signs improving
- All fields involved in search for life computation, computer simulation (stars, planets, molecules interactions)
- 3 important
o Astronomy
o Planetary science
Atmospheric science
o Biology
How does astronomy help us understand the possibilities for extraterrestrial life?
- Most of human history, universe conception very diff than now
o Geocentric (Earth-centered) view of the Universe: all stars, planets revolve around Earth
Dominated for thousands of years
- .: Astronomy is key Earth regular planet revolving around regular star in context of VAST cosmos (.: lots potential life)
o By studying distant objects, we’ve learned physical laws operate in rest of universe are same as those that operate on Earth
o .: if something happens here, theoretically can happen elsewhere
o .: we’re not special in any way
How does planetary science help us understand possibilities for ET life?
- Planetary science = study of almost everything related to planets
o Planets, moons orbiting, how planets form, objects forming in association (comets, asteroids)
- 2 important ways
- 1) learning how planets form allows understanding of how common planets are
o Otherwise how to know stars can have planets around them
o last half of 20th century, moon/planet evidence helped understanding of how our own solar system formed .: more likely
stars similarly born with planets
o 1995, first extrasolar planet (planets orbiting stars other than our Sun) discovered
o Now a lot discovered
.: lots stars with planets .: lots possibilities of life
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