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Where is this?
Level 3
No
Class
Present
Present
Level 4 Planetary
Party
Class
End
Reviews
Life
Beyond
Earth
photo: Emory Kristof
The Drake Equation
N = R* fp ne fl fi fc L
N
# civilizations with detectable electromagnetic emissions
R*
fp
ne
rate of star formation (stars/year) suitable for intelligent life
fraction of stars with planetary systems
# of worlds/system with environment suitable for life
fl
fi
fc
L
fraction of planets on which life appears
fraction of life-bearing planets on which intelligent life emerges
fraction of civilizations revealing existence
length of time civilizations release detectable signals (years)
10
exoplanets.org | 4/8/2015
0.1
0.1
0.01
-3
10
0.100
0.700
1.300
1.900
3.100
2.500
Mass of Star (Solar Masses)
1990
1995
2000
2005
First Publication Date
2010
2015
Semi-Major Axis (AU)
1
1
0.01
Msin(i) [Jupiter Mass]
10
exoplanets.org | 4/8/2015
Planet Mass (Jupiter Masses)
10
1
J
0.1
N
radial velocity
transit
microlensing
direct imaging
0.01
E
-3
10
0.01
0.1
1
Separation (AU)
10
100
Kepler Results (all stellar types, Fressin+ 2013)
what about
longer
orbital P?
occurrence not strong dependence on host star type
The Scorecard
as of 12 April 2017
Indirect Methods
1. (pulsar) timing
19 systems 24 planets
2. radial velocities 534 systems 711 planets
3. astrometry
1 system
1 planet
4. transits
2035 systems 2720 planets
Direct Methods
5. imaging
exoplanets.org
76 systems
83 “planets”
exoplanets.eu
Life
Beyond
Earth
photo: Emory Kristof
SETI Water Hole
SETI Surveys
Ozma
Project Phoenix
Allen Array
Telescope(s)
Greenbank 26m
Arecibo 305m
Parkes 64m
Greenbank 43m
350 x 6.1m
(= 101m dish)
Frequencies
1.4198 to 1.4202 GHz
1.0 to 3.0 GHz
0.5 to 11.2 GHz
Resolution
100 kHz
1 Hz
???
# channels
4
2 x 106
???
Weeks/year
4 (once)
3 (repeating)
52
???
NASA, then private
SETI Institute
# target stars
2
103
106
# completed
2
~ 50%
first light 2004
# ET signals
0
0
???
Funding
Project Phoenix
began as NASA’s High Resolution Microwave Survey (HRMS)
Targeted Search (Ames) and Sky Survey (JPL)
first observations, October 12, 1992
cancelled by Congress in 1993
renamed Project Phoenix
private funding sources sought
private funding sources found
Arecibo 305m (largest in N)
Jodrell Bank (England)
Greenbank 43m
Parkes 64m (largest in S)
Project Phoenix Detects ET!
time
frequency
test case: Pioneer 10 beyond 70 AU
signal allowed to drift in frequency from Earth motion
separates terrestrial from extraterrestrial signals
Allen Array
dedicated SETI effort
SETI Institute and UC Berkeley
Hat Creek Observatory, Mt. Lassen, California
350 antennas of 6.1m diameter = 100m radio telescope
$25M from Paul Allen (Microsoft co-founder)
Allen Array
Gregorian design
350 X 6.1m dishes
Allen Array
Project Phoenix got 3 weeks/year at Arecibo
Allen Array will increase efficiency by 100X
full time SETI operation
daytime observations ok (Arecibo has Sun problem)
different stars (Arecibo limited to near-ecliptic sources)
multiple dishes … ~20 stars searched simultaneously
expansion easy
… target list grows from 1,000 stars to 1,000,000 stars
Nearby Stars
Project Phoenix
Allen Telescope Array
50 pc
300 pc
How Far for 1 Million Stars?
G
362 parsecs
1180 light years
F-K
240 parsecs
782 light years
A-M (now)
147 parsecs
479 light years
A-M (pred)
126 parsecs
411 light years
The Dream … 1000 Light Year Catalog
(307 pc)
10 Parsec Census 2017.0
wd
20
5%
O,B
0
0%
A
4
1%
F
7
2%
G
19
5%
K
43
12 %
M
279
75 %
bd
44
pl
26+8
Three Laws of M Dwarfs
1.
2.
3.
M dwarfs dominate the stellar population.
M dwarfs dominate the stellar mass budget.
M dwarfs are more varied than any other spectral type.
Solar Family
How are they different?
The Seven Dwarfs
Nice Earth
Voyager’s Farewell
The Brothers Henry
Solar System Explorers Triple
Name your 3 favorite things that you learned in ASTR 8850 this year.
1. Ura and Nep have non-centered magnetic field cores
2. Sat has hexagonal features at its north pole
3. orbiting spacecraft can measure moment of inertia for world and yield info about interior
4. regolith is tiny powdered gravel due to micrometeorite impacts
5. Antarctica is a good place to find meteorites
6. Titan has magic islands possibly due to waves on surface
7. Mercury and Titan are nearly identical sizes
8. Europa’s craters are filled with fresh H2O ice indicating subsurface ocean
9. Hyperion is very porous with a density of 0.7
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Solar System Explorers Triple
Name your 3 favorite things that you learned in ASTR 8850 this year.
1. Earth has six major greenhouse gases
2. Titan has CH4 lakes
3. in Nice Model, Nep and Ura may have switched places
4. paleomagnetic patterns indicate flipping of Earth’s magnetic field
5. Mars’ obliquity varies chaotically because it has no large moon
6. Ura and Nep rings were found by stellar occultations
7. some of Jupiter’s colors are caused by contributions from Io
8. Sat is oblate because it is puffy and rotates quickly (10 hours)
9. 20% of Mars’ atmosphere may freeze onto one hemisphere in the winter
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Solar System Explorers Triple
Name your 3 favorite things that you learned in ASTR 8850 this year.
1. Io torus happens
2. more than 700,000 asteroids have a < 5.2 AU
3. Antarctica is weighted down by ice on top of it
4. Mercury is in a 3:2 spin:orbit resonance with the Sun
5. on the equator during the day, Mars can be as warm as this room (300K)
6. radio bursts from Jup magnetic fields used to define rotation period
7. Enceladus has tiger stripes that are warmer than the rest of the world
8. Venus has pancakes caused by molten activity, but is not as dense as Earth, which is 5.5 g/cm3
9. planets and other worlds are complex and diverse so exoplanet drawings are SILLY
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