Transcript Origin of Stars, Planets, and Life in the Universe

The Origin and possible
existence of Life in the
Universe
Poll Question:
Do you think there is life
 even just primitive
forms of life  on other
worlds?
Do you think there is intelligent
life on other worlds?
YES
NO
UNDECIDED
The Electromagnetic Spectrum
Use a stamp “X” to select the most
abundant element in the universe.
neon
nitrogen
hydrogen
oxygen
helium
carbon
sodium
iron
Axis of rotation
Approx. 1 light year
Axis of rotation
Rotation retards
collapse in this
direction
Slowly spinning
interstellar cloud
Gravity makes cloud
shrink. As it shrinks it spins
caster and flattens into a
disk with central bulge.
Approx.
100 AU
Big Questions in Science
Questions about origins:
• Where did we come from?
• Are we alone?
Other astrobiology questions:
1. How did life on Earth form?
2. Should we expect life on many other worlds?
3. Is life on other worlds like life on Earth?
4. How can we detect life elsewhere?
Poll Question:
What chemical elements
were created by the Big
Bang?
The Life Cycle of Stars…
H2
NH3
CH4
H2O
Put a stamp on the most
abundant element in life on Earth.
neon
nitrogen
hydrogen
oxygen
helium
carbon
sodium
iron
The Most Abundant Chemical Elements
 in the Universe and in Life
In the Universe
•
•
•
•
•
H
He
O
C
N
In Life
•
•
•
•
•
H
O
C
N
A few facts about
Life on Earth
• Life on Earth is carbon-based.
• Life on Earth requires liquid water
• The amino acids in life are easily
formed.
Finding Life
• First find planets.
One way uses the Doppler Effect.
Another way to find planets is to look for
transits.
Kepler
Terrestrial Planet
Finder
Signs of Life
(not yet possible to detect with current technology)
•
•
•
•
Seasonal changes
Unusual abundances of gases
Gases produced by life
Unusual patterns of electromagnetic
radiation (e.g., radio or TV broadcasts,
the nighttime glow of cities)
Bacterial fossils
3 billion years old on the earth.
Will we find them on Mars or elsewhere?
Records of Life on Earth
Life elsewhere could be similar to any of
These stages, or entirely different.
Current Life Forms
We can study these in detail to get DNA,
etc.
Amino Acids: building blocks of
life.
Some of these were produced in the lab by Harold Urey out
of primeval gases like methane, ammonia, carbon dioxide-by zapping them with electricity (lightning). (1950s)
Human DNA
Nobody has produced this
artificially or even hopes
to. Too complicated.
50,000 genes.
However, the total makeup
Of a human being requires
More information.
N=no.
of civilizations.
R=radius of
spherical galaxy
r = average
separation.
4 pi (r/2)2 N
= 4 pi R3/3
implies
r = 2R/N1/3.
The distance between civilizations in the
Milky Way
The Drake Equation
The Drake Equation
• N = N* fp ne fl fi fc fL
• N* represents the number of stars in the Milky Way
Galaxy
• Question: How many stars are in the Milky Way Galaxy?
• Answer: Current estimates are 100 billion.
• fp is the fraction of stars that have planets around them
• Question: What percentage of stars have planetary
systems?
• Answer: Current estimates range from 20% to 50%.
• ne is the number of planets per star that are capable of
sustaining life
• Question: For each star that does have a planetary
system, how many planets are capable of sustaining
life?
• Answer: Current estimates range from 1 to 5.
The Drake Eqn. continued
• N = N* fp ne fl fi fc fL
• fl is the fraction of planets in ne where life evolves
• Question: On what percentage of the planets that are capable of
sustaining life does life actually evolve?
• Answer: Current estimates range from 100% (where life can evolve
it will) down to close to 0%.
• fi is the fraction of fl where intelligent life evolves
• Question: On the planets where life does evolve, what percentage
evolves intelligent life?
• Answer: Estimates range from 100% (intelligence is such a survival
advantage that it will certainly evolve) down to near 0%.
• fc is the fraction of fi that communicate
• Question: What percentage of intelligent races have the means and
the desire to communicate?
• Answer: 10% to 20%
The Drake Eqn. continued
• N = N* fp ne fl fi fc fL
• fL is fraction of the planet's life during which the
communicating civilizations live
• Question: For each civilization that does communicate,
for what fraction of the planet's life does the civilization
survive?
• Answer: This is the toughest of the questions. If we take
Earth as an example, the expected lifetime of our Sun
and the Earth is roughly 10 billion years. So far we've
been communicating with radio waves for less than 100
years. How long will our civilization survive? Will we
destroy ourselves in a few years like some predict or will
we overcome our problems and survive for millennia? If
we were destroyed tomorrow the answer to this question
would be 1/100,000,000th. If we survive for 10,000 years
the answer will be 1/1,000,000th.
• N, the number of communicating civilizations in the
galaxy.
SETI—Search for Extraterrestrial
Intelligence
Over 30 messages
suspiciously intelligent.
They are using home
computers to scan for
messages.
Mars had ( and has) water.
Does it have current life?
Summary
• We have learned an enormous amount about
the origins of stars and planets.
• We are just starting to learn about life in the
universe.
• These explorations require a team effort
involving scientists from many disciplines.
• There is still much more to explore. Students
will be able to make discoveries and help us
learn even more!
NASA’s Navigator Missions:
http://planetquest.jpl.nasa.gov/
Origins Education Forum:
http://origins.stsci.edu/
Poll Question:
Do you think there is life
 even just primitive
forms of life  on other
worlds?
Do you think there is intelligent
life on other worlds?
YES
NO
UNDECIDED