Astronomy 2021 Life in the Universe
Ch. 1 Intro to Astrobiology
Ch. 2 Science of Life in the Universe
This is an Exciting time to be Studying Life in the Universe
Mars Science Laboratory: Curiosity Rover
NASA Kepler Spacecraft
o Stopped functioning mid 2013
o Telescope in space looking for new planets
o Goal: to detect analogs of the earth around other stars
To find potentially habitable planets
Looking for fraction of planets that are like earth
Expect arrival of the New Horizons Spacecraft
o Launched in 2006 with the goal to encounter Pluto (farthest “planet”)
o Encountered Jupiter at one point; expect the encounter in July 2015 (will
only be one day to see Pluto before it goes into the outer reaches of the
Looking for the next target for the new horizons mission after it
Chapter 1: A Universe of Life?
The Possibility of Life Beyond Earth
What are we searching for?
o Something that self replicates?
Fire self replicates but it is not life
o Something that eventually dies?
Is it reasonable ot imagine life beyond Earth?
o Was life on earth for billions of years
o Not necessarily humanoids
Is it reasonable to imagine Life on Earth?
Venus and Mars are said to be the closest and most similar to earth
o Not breathable
o Smaller planet; has white caps (ice) on the poles
o Has a lot of water in the ice caps
o In late 19 and earlier 20 century, astronomers thought they saw
organization on the planet using telecopes
Thought they saw canals formed for irrigation by martians
o Has a somewhat closer resemblance to earth
Mars has an atmosphere Good conditions in the past for life to exist on mars
• It was warmer, common minerals
Reasonable to think in the history of the solar system, life may
have existed on other planets
Moons of Jupiter
o All have large subsurface reservoirs of water
o Europa is entirely covered in water ice; under the ice is a resevoir of liquid
Planets beyond the solar system (exoplanets)
o Believe that every star is surrounded by orbiting planets
o Many planets that are considered habitable
o About the size of the earth and within the habitable zone around their host
o Probable that similar conditions exist in other planetary systems
While it is possible that life exists only on Earth, we have plenty of scientific
reasons to think that life may be widespread and we could detect it!
The Scientific Context of the Search
How does astronomy help us understand the possibilities of extraterrestrial life?
How does planetary science help us understand the possibilities of extraterrestrial
How does biology help us understand the possibilities?
Ptolemy made a diagram
o Put the earth at the centre of the universe
The universe is not geocentric
o Copernicus told us this
There are many worlds, not just earth
They all follow the same physical rules as our own
o Laws of physics remain constant
We live on a planet
In the past 2 decades we have discovered ~1000 more extrasolar plants: around
o Exponential discovery rate
o Rate at which planets are discovered doubles every couple years
What are these planets? How do they work? What sort of temperatures,
chemicals, air, do they have?
Are they habitable? If so, what sort of life could they sustain?
If we are looking for life, need to understand life How does it originate and survive? Is it rare or common?
o Life exists in very extreme environments
Physics is the same everywhere in the universe. Chemistry is too; is biology?
Would it follow the same path as on Earth?
o Are humans the end goal of evolution?
Moon is actually dislodged material from the earth
o Happened 4 billion years ago
o Very first sign of life was 3.9 billion years ago
o Tells you that life is a necessary event if there is a suitable environment for
Biology may be common in the universe
o Evidence that organize molecules form easily and naturally
o Evidence that life appeared early in the history of the Earth
o Evidence that Earth life can survive under a wide range of conditions
Places to Search
Where should we search for life in the universe?
Could aliens be searching for us?
Searching the Solar System
o Too close to the sun; too cold or too hot depending on which side is facing
o Hot almost throughout
o Life sustaining
o Perhaps in the past
Jupiter & Saturn are actually gas masses
o Although some findings may have life sustaining parts
Uranus and Neptune
o Also gas masses slightly smaller than above
o Just too cold to have water in liquid form
Mars is the closest thing to possibility for life sustaining environment
o In the past it was probably warmer and more liquid
Moons of Jupiter are possibly a good place but we have not landed there yet
Titan: Methane rains and forms lakes
Searching among stars
Graph that measures radius and distance from the middle of the habitable zone
o Shows where the discovered planets are
o Most are so close to the sun that they would be too hot to be habitable
Radio telescope in West Virginia was used in 1996 to search for signals from
extraterrestrial civilizations o Could aliens be searching for us?
o Baiss for Search for Extraterrestrial Intelligence (SETI) project
The New Science of Astrobiology
How do we study the possibility of life beyond earth?
o Study the conditions confucive to the origin and ongoing existence of life
o Look for such conditions on other planets in our solar system and around
o Look for the actual occurrence of life elsewhere
Of all the planets, on 9 have been directly imaged; the rest were just inferred to
o Can tell atmospheric composition of the planet
Weather on Other Worlds
Weather exists everywhere
The Possibility of Life Beyond Earth
Is it reasonable to imagine life beyond Earth?
Where do we search?
How do we search?
Chapter 3.4: Light and Matter: Reading Messages from the Cosmos
Light is the only carrier of information that we have when studying other
o Important to know what it can tell us about matter
How can we use light to read messages?
Spectrum of the sun
o Black notches: tells the composition of the atmosphere of the sun
Light in Everyday Life
How do we experience light?
o The warmth of sunlight tells us that light is a form of energy
o We can measure the flow of energy in light in units of watts: 1 watt = 1
Joule: unit of energy
Watt: unit of power
Colours of light
o Newton showed that white light is composed of all the colours of the
o Constituent colours of white light
o When light gets reflected in water droplets it projects as a rainbow in the
Water droplets are like small prisms Solar ray gets refracted from a droplet which gets reflected on the
surface of the droplet and then gets refracted again
Angle of refraction is somewhat different for red light and violet
light which produces the rainbow
How do light and matter interact?