Extra-Solar Planets
Theodore Jacobson Observatory
University of Washington
Brian Stephanik
October 5th, 2005
www.astro.washington.edu/observatory/
Topics for tonight
What are (extra-solar) planets?
Very brief history
Detection
The present
The future
Where do planets fit in?
Asteroids, planets, and stars: where to draw the line?
Rocky core – gaseous atmosphere – nuclear fusion
On-going debate: Pluto
History
A very new science
– Last 15 years
1989 – Mention of (possible) extra-solar planets
in a research paper
1993 – Confirmed detection
1995 – Main sequence detection: 51 Pegasi
Late 1990s – Large number of discoveries due to
advances in technology
– CCDs, telescopes, etc.
Detection
Stars outshine their planets
– Direct detection is difficult
Need to be clever
1. Astrometry
2. Occultation
3. Doppler
4. Microlensing
(Scary names, not so scary ideas)
Detection #1: astrometry
“Star wobble”
– Playground connection
• Teeter-Totter & Center of
Mass
– Key idea: Objects orbit
around the center of mass -
even stars!
– Viewed from “above”
– First attempted: 1943
– Not used today: technology
Detection #2: occultation
Who turned off the
lights?
– Venus transit & lunar
eclipse
What happens on Earth
during a lunar eclipse?
Key idea: planets block
light from stars
Detection #2: occultation
Detection #3: Doppler
Radial velocity
– Doppler effect for sound
• What sound does a
speeding ambulance
make?
– Radar guns
– Viewed “edge-on”
– Key idea: moving sources
appear to change their
frequency
Detection #4: microlensing
Einstein
– Massive objects bend light.
– Some of this (extra) bent
light arrives at Earth.
– Causes objects to appear
brighter (more light rays).
– Key idea: objects with mass
bend light (toward Earth,
perhaps)
– What do one of these look
like? And how would a
planet affect it?
Detection #4: microlensing
This is not the
light form the
host star.
Detection: a summary
Astrometry
– Star wobble
Occultation
– Transit
Doppler effect
– Think speeding sirens
Microlensing
– Oddness of otherwise smooth light curve
So what do we know?
The present
Today: 160+ known
ESPs
June 2005: Gliese
867
Most ESPs are
HUGE!
– Why is this?
Why are ESPs big
Teeter-totter
– BIG
• 1st grader invites friends
• 5th grader must move out to balance
• 5th grader (sun) farther from center of mass
– CLOSE
• Time…
• Closer planets move faster
The present: first image
What does tomorrow hold?
The future
TPL: Terrestrial Planet Finder
2014 and 2020 launches
Interferometry: directly observe light from a planet
Spectroscopy on atmosphere of planet
The future is tomorrow!
Thursday, Oct 6, 4:00pm
Physics/Astro Auditorium: A102
Jian Ge, University of Florida: An All Sky
Extrasolar Planet Survey with the Sloan
Telescope
Detection between 2008-2020
– Monitor 1,000,000 nearby stars
– Tens of thousands of new ESPs possible
Thank you
Questions?