Transcript Document

Looking for intelligent life
in the Milky Way galaxy
• First
Any evidence of planets outside of the solar
system? Yes!
• Second
How to detect intelligent life. Radio
communication.
• Third
Probability of locating intelligent life elsewhere.
Slide 1
Slide 2
p.416
About 150 planets
discovered around
other stars.
Most are massive and
close to the star!
Why?
vstar α Mplanet/√a
The closer the planet
the star and the larger
the mass, the larger the
velocity of the star.
That is why most
of the discovered planets
have a distance of less
than 1 AU and mass like
Jupiter.
Slide 3
p.188
Theory on formation of planets
As protostars collapse under gravity the material flattens!
Solar system: all major the planets are in one plane!
Any evidence besides Solar system? Yes!
Slide 4
Fig. 9-5, p.191
Conservation of angular
momentum:
Mω²r = constant
The smaller is r, the
faster the angular
velocity ω.
As stellar system
contracts under
gravity, it speeds up,
which flattens the
system. Ultimately
the flattened material
forms the planets.
Slide 5
Fig. 9-3, p.190
Β Pectoris
dust ring,
Slide 6
Fig. 9-11, p.197
Protoplanetary disks around a star
Slide 7
Fig. 9-12a, p.198
An edge-on dust ring blocks light from reflection nebulae around
a young solar-type star
Slide 8
Fig. 9-14, p.198
a
Vstar α Mplanet/√a
Slide 9
Detection of planets using Doppler shift
Fig. 9-6, p.193
Slide 10
Fig. 9-7, p.194
Discovery of planets using occultation
Slide 11
Fig. 9-8a, p.195
We also have one direct evidence of a planet!
Slide 12
Fig. 9-8b, p.195
How to detect
intelligent life?
Radio waves!
Arecibo Radio
Telescope in
Puerto Rico
Very Large Array
VLA
Slide 13
Fig. 20-17, p.428
The message sent
to the globular
cluster M13
Slide 14
Fig. 20-13, p.424
Probability of Finding
Technological Civilizations
In the
Milky Way Galaxy
1. Number of stars in Milky Way
2. Single stars (0.5)
3. F, G and K stars only. (0.1)
Only Sun like stars.
4. Fraction of single stars with planets. (1)
5. Fraction with habitable planets (0.1)
6. Probability to start life. (1)
7. Produce intelligence. (0.1)
8. Communicative intelligence. Radios (0.1)
Ants, bees do not communicate.
21011.
11011 .
11010.
11011.
1109.
1109.
1108.
1107.
9. Longevity of the technological society, (10-6)
10 stars
•If longevity is 10,000 years out of 11010 years, then fraction is (10-6).
•If lifetime is forever once it starts. It took on Earth almost 5 billion years
for communicative technology to get started. The Sun will live 10 billion years.
9. Longevity of the technological society, (0.5)
5106 stars.
•If 5,000,000 star systems have communicative intelligence, then the probability
of the nearest with star with communicative intelligence is 600 light years.
Slide 15
Slide 16
Fig. 20-18, p.428