AST s309L
„Exoplanets and Extraterrestrial Life‘‘
Second Summer Session
11 July – Aug 12, 2011
M,T,W,Th,Fr 1:30-3:00 pm
RLM 15.216B
Michael Endl
Office: RLM 16.328
Tel: (512) 471 8312
Email: mike@astro.as.utexas.edu
http://austral.as.utexas.edu/michael/teaching/
Week 1:
July 11, Mon: "Introduction Part I: Exoplanets"
July 12, Tue: "The Doppler Method: Technique"
July 13, Wed: "The Doppler Method: Results"
July 14, Thu: "Astrometry: Technique and Results"
July 15, Fri: "Microlensing & Timing Method: Technique and Results"
Week 2:
July 18, Mon: "The Transit Method: Technique"
July 19, Tue: "The Transit Method: Results"
July 20, Wed: "Direct Imaging"
July 21, Thu: "Exoplanet Atmospheres"
July 22, Fri: "Exoplanet Host Stars"
Week 3:
July 25, Mon: "Planets in Exotic Locations"
July 26, Tue: "The CoRoT Mission"
July 27, Wed: "The Kepler Mission"
July 28, Thu: "Toward Other Earths"
July 29, Fri: "Exam 1: Exoplanets"
Week 4:
Aug 1, Mon: "Introduction Part II: Extraterrestrial Life"
Aug 2, Tue: "The Evolution of Life on Earth“
Aug 3, Wed: "The Search and Prospects for Life on Mars“
Aug 4, Thu: "The Outer Solar System and Beyond“
Aug 5, Fri: "Terrestrial Planet Finder"
Week 5:
Aug 8, Mon: "The Search For Extraterrestrial Intelligence (SETI)"
Aug 9, Tue: TBA
Aug 10, Wed: TBA
Aug 11, Thu: TBA
Aug 12, Fri: "Exam 2: Extraterrestrial Life"
Literature:
Exoplanets:
„Planet Quest“, Ken Croswell
„Toward Other Earths“, Alan Boss
„The Crowded Universe“, Alan Boss (2009)
Extraterrestrial Life:
„Lonely Planets“, David Grinspoon (2004)
„The Living Cosmos“, Chris Impey (2007)
„The Eerie Silence“ , Paul Davis (2010)
Resources
The Extrasolar Planet Encyclopaedia (Jean Schneider):
www.exoplanet.eu (note www.exoplanets.eu sends you to
the Geneva Planet Search Program)
• In 7 languages
• Tutorials
• Interactive catalog (radial velocity, transits, etc)
• On line histrograms and correlation plots
• Download data
Resources: The Nebraska Astronomy Applet Project (NAAP)
http://astro.unl.edu/naap/
This is the coolest astronomical website for learning basic
astronomy that you will find. In it you can find:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Solar System Models
Basic Coordinates and Seasons
The Rotating Sky
Motions of the Sun
Planetary Orbit Simulator
Lunar Phase Simulator
Blackbody Curves & UBV Filters
Hydrogen Energy Levels
Hertzsprung-Russel Diagram
Eclipsing Binary Stars
Atmospheric Retention
Extrasolar Planets
Variable Star Photometry
Resources
The Nebraska Astronomy Applet: An Online
Laboratory for Astronomy
http://astro.unl.edu/naap/
http://astro.unl.edu/animationsLinks.html
Pertinent to Exoplanets:
1. Influence of Planets on the Sun
2. Radial Velocity Graph
3. Transit Simulator
4. Extrasolar Planet Radial Velocity Simulator
5. Doppler Shift Simulator
6. Pulsar Period simulator
7. Hammer thrower comparison
For iPhone users there is a free exoplanet app
There are ~200 billion stars in our galaxy…
…one of them is our Sun.
Are there other planets in the universe?
Is there another Earth out there?
2
Some planets were known to the ancients who
watched them move against the night sky.
2
Mercury, Venus, Mars, Jupiter, and
Saturn were the “Wandering Stars.”
“Planet” comes from the Greek word for “wanderer.”
A quick tour of our solar system
A good source for this is:
http://www.nineplanets.org
and
http://solarsystem.nasa.gov
The Structure Of Our Planetary System:
Mercury
Distance: 0.38 AU
Period: 0.23 years
Radius: 0.38 RE
Mass: 0.055 ME
Density 5.43 gm/cm3 (second densest)
Satellites: None
Structure: Iron Core (~1900 km), silicate mantle (~500 km)
Temperature: 90K – 700 K
Magnetic Field: 1% Earth
Atmosphere: Thin, bombarded by Solar Wind and constantly
replenished
Venus
Distance: 0.72 AU
Period: 0.61 years
Radius: 0.94 RE
Mass: 0.82 ME
Density 5.4 gm/cm3
Satellites: None (1672 Cassini reported a companion)
Structure: Similar to Earth Iron Core (~3000 km), rocky mantle
Temperature: 400 – 700 K (Greenhouse effect)
Magnetic Field: None (due to slow rotation)
Atmosphere: Mostly Carbon Dioxide (massive Greenhouse effect)
Pancake volcanoes
Magellan Radar Imaging
Sif Mons
Earth
Distance: 1.0 AU (1.5 ×1013 cm)
Period: 1 year
Radius: 1 RE (6378 km)
Mass: 1 ME (5.97 ×1027 gm)
Density 5.50 gm/cm3 (densest)
Satellites: Moon (Sodium atmosphere)
Structure: Iron/Nickel Core (~5000 km), rocky mantle
Temperature: -85 to 58 C (mild Greenhouse effect)
Magnetic Field: Modest
Atmosphere: 77% Nitrogen, 21 % Oxygen , CO2, water
Earth Moon System from Surveyor
and Mars Express: The Double
Planet
Mars
Distance: 1.5 AU
Period: 1.87 years
Radius: 0.53 RE
Mass: 0.11 ME
Density: 4.0 gm/cm3
Satellites: Phobos and Deimos
Structure: Dense Core (~1700 km), rocky mantle, thin crust
Temperature: -87 to -5 C
Magnetic Field: Weak and variable (some parts strong)
Atmosphere: 95% CO2, 3% Nitrogen, argon, traces of oxygen
Phobos
13 x 11 x 9 km
Deimos
7.5 x 6 x 5 km
Are believed
To be captured asteroids
Jupiter
Distance: 5.2 AU
Period: 11.9 years
Diameter: 11.2 RE (equatorial)
Mass: 318 ME
Density 1.24 gm/cm3
Satellites: > 20
Structure: Rocky Core of 10-13 ME, surrounded by liquid
metallic hydrogen
Temperature: -148 C
Magnetic Field: Huge
Atmosphere: 90% Hydrogen, 10% Helium
Aurorae on Jupiter
Saturn
Distance: 9.54 AU
Period: 29.47 years
Radius: 9.45 RE (equatorial) = 0.84 RJ
Mass: 95 ME (0.3 MJ)
Density 0.62 gm/cm3 (least dense)
Satellites: > 20
Structure: Similar to Jupiter
Temperature: -178 C
Magnetic Field: Large
Atmosphere: 75% Hydrogen, 25% Helium
Uranus
Distance: 19.2 AU
Period: 84 years
Radius: 4.0 RE (equatorial) = 0.36 RJ
Mass: 14.5 ME (0.05 MJ)
Density: 1.25 gm/cm3
Satellites: > 20
Structure: Rocky Core, Similar to Jupiter but without metallic
hydrogen
Temperature: -216 C
Magnetic Field: Large and decentered
Atmosphere: 85% Hydrogen, 13% Helium, 2% Methane
HST Image
Voyager
Neptune
Distance: 30.06 AU
Period: 164 years
Radius: 3.88 RE (equatorial) = 0.35 RJ
Mass: 17 ME (0.05 MJ)
Density: 1.6 gm/cm3 (second densest of giant planets)
Satellites: 7
Structure: Rocky Core, no metallic Hydrogen (like Uranus)
Temperature: -214 C
Magnetic Field: Large
Atmosphere: Hydrogen and Helium
2006 IAU Definition of a Planet
1. is in orbit around the Sun,
2. has sufficient mass to assume hydrostatic
equlibrium (a nearly round shape), and
3. has „cleared the neighborhood" around its orbit.
If a non-satellite body fulfills the first two criteria it is termed a
„dwarf planet“. Originally, the IAU wanted to consider all
dwarf planets as planets.
Under the new definition Pluto is no longer a planet, but rather a
dwarf planet.
9
Pluto before 2006
Pluto at the IAU 2006
Pluto today
Completing the Census: Satellites
8
Europa
Titan
Io
Triton
Planetary Rings
Jupiter
Saturn
Uranus
Neptune
Trans-Neptunian Objects
5
7
Plutoids
Name
Orcus
Ixion
Huya
Varuna
Quaoar
Sedna
Pluto
Radius
(km)
1100
980
480
780
1290
1800
2274
Distance
(AU)
39
40
40
43
44
486
39.5
Comets
Debris Disks
Extrasolar Planets
Why Search for Extrasolar Planets?
• How do planetary systems form?
• Is this a common or an infrequent event?
• How unique are the properties of our own solar system?
• Are these qualities important for life to form?
Up until now we have had only one laboratory to test planet
formation theories. We need more!
The Concept of Extrasolar Planets
Democritus (460-370 B.C.):
"There are innumerable worlds which differ in size.
In some worlds there is no sun and moon, in others
they are larger than in our world, and in others more
numerous. They are destroyed by colliding with each
other. There are some worlds without any living
creatures, plants, or moisture."
Giordano Bruno (1548-1600)
Believed that the Universe was infinite and that other
worlds exists. He was burned at the stake for his
beliefs.
What kinds of explanetary systems do we expect to find?
The standard model of the
formation of the sun is that
it collapses under gravity
from a proto-cloud
Because of rotation it
collapses into a disk.
Jets and other mechanisms
provide a means to remove
angular momentum
The net result is you have a protoplanetary disk out
of which planets form.
The net result is you have a protoplanetary disk out
of which planets form (mostly) by a process called
accretion.
Expectations of Exoplanetary Systems from our
Solar System
• Solar proto-planetary disk was viscous. Any
eccentric orbits would rapidly be damped out
– Exoplanets should be in circular orbits
• Giant planets need a lot of solid core to build up
sufficient mass to accrete an envelope. This core
should form beyond a so-called ice line at 3-5 AU
– Giant Planets should be found at distances > 3 AU
• Our solar system is dominated by Jupiter
– Exoplanetary systems should have one Jovian planet
• Only Terrestrial planets are found in inner regions
• Expect that satellites and rings to be common
So how do we define an extrasolar Planet?
There is no official IAU definition of an exoplanet.
We can simply use mass:
Star: Has sufficient mass to fuse hydrogen to helium.
M > 80 MJupiter
Brown Dwarf: Insufficient mass to ignite hydrogen, but
can undergo a period of Deuterium burning.
13 MJupiter < M < 80 MJupiter
Planet: Formation mechanism unknown, but insufficient
mass to ignite hydrogen or deuterium.
M < 13 MJupiter
IAU Working Definition of Exoplanet
1.
2.
3.
Objects with true masses below the limiting mass for
thermonuclear fusion of deuterium (currently calculated to be 13
Jupiter masses for objects of solar metallicity) that orbit stars or
stellar remnants are "planets" (no matter how they formed). The
minimum mass/size required for an extrasolar object to be
considered a planet should be the same as that used in our Solar
System.
Substellar objects with true masses above the limiting mass for
thermonuclear fusion of deuterium are "brown dwarfs", no matter
how they formed nor where they are located.
Free-floating objects in young star clusters with masses below the
limiting mass for thermonuclear fusion of deuterium are not
"planets", but are "sub-brown dwarfs" (or whatever name is most
appropriate).
In other words „A non-fusor in orbit around a fusor“
How to search for Exoplanets
Indirect Techniques
1.
Radial Velocity (or Doppler Method)
2. Astrometry
3. Transits
4.
Microlensing
Direct Techniques
4. Spectroscopy/Photometry: Reflected or Radiated light
5. Imaging