Transcript 14 planets, life - Solar Physics at MSU

Agenda


Planet formation
The search for life in the universe
What is this picture?
A.
B.
C.
D.
A distant star
Neptune
Earth
A galaxy
The “pale blue dot”:
Earth viewed from the edge of our
solar system (taken by Voyager
1).
How hard would it be to learn
about Earth from a long way
away?
Aside:
Disks in astronomy



Accretion disks
around black holes
Planetary rings
Spiral galaxies
HST
Cassini
astronomy.com
When a star is born…


There is a disk of material left over.
Rotates in the same direction as the
protostar.
Notice the scale!
Planet formation



Dust and gas is left over from star
formation (1-100 AU in diameter)
Gravitational attraction brings particles
together – creates a disk of material
Happens quickly - 3 to 30 million years
Similar to Shepherd moons
Disks around protostars
The hunt for new planets



Seeing them directly is nearly
impossible.
Star wobbles because of the tug from
its planet.
The wobble causes a Doppler shift that
we can observe!
(motion of the star is greatly exaggerated!)
The most easily found
exo-planets are ____.
A.
B.
C.
D.
Light and far from their star
Light and close to their star
Massive and far from their star
Massive and close to their star
Fgravity 
Gmstar m planet
r
2
To date…

Way over 200 extra-solar planets have
been found


276 as of March, 2008
Most are:


Massive
Close to their star
Kepler mission



NASA's first mission
capable of finding Earthsize and smaller planets
around other stars.
Works by transit method.
Launch scheduled for
February, 2009.
Can life exist anywhere?
What is required for life to
exist?
What is required for life?




Water
Oxygen?
Energy input (usually sunlight)
Carbon?
Location matters!
Sun from Mercury
Location matters!
Sun from Saturn
On the other hand…



Extremophiles live in very harsh
conditions
Bacteria in Yellowstone
Bacteria under ice in the Arctic
Star type matters



Remember OBAFGKM?
Sun is G2.
Is type B hotter or cooler than the
Sun?
A.
B.
C.
D.
Hotter
Cooler
Same temperature
Cannot tell
UV Radiation

Which has more UV in its spectrum: Sun or
a B-type star?
A.
B.
C.
D.

Sun
B star
Same
Can’t tell
B is hotter, so it has more UV.


UV breaks down organic chemicals
Not conducive to life.
How should we go about
looking for life elsewhere?
A.
B.
C.
D.
E.
Go there!
Send out signals
Look for others sending signals
Look for chemical signatures of life
We should not look for life
Go there?

Example: NASA New Horizons mission



To get to the nearest star (4 ly away)



Going to pluto and outer solar system
Travels 47,000 mph
57,000 years
OR, 2855 generations of people!
What would be required to make this work?
(discuss)
Send out a signal?




Radio technology on Earth is about
100 years old.
Only stars within 50 ly could have
gotten a signal and responded so far
(About 1400 stellar systems)
No return signal yet!
Marconi company, England, 1906
(wikipedia)
Listen? — SETI

Project Phoenix



Observing since February, 1995
Looking at nearby, Sun-like stars only
Nothing yet!
SETI Institute
Would we know life if we saw
it?
How do we know
these are alive?
coral
lichen
Look for chemical signature




Water vapor
CO2 (carbon dioxide)
Methane
Oxygen
Clicker registration!

If you don’t see your number, it means
that your clicker is already registered.
Summary


Planets form quickly!
Looking for life:



Location matters
Look for byproducts of life
Exam 2 is Thursday at 6 pm!