Extra-Solar Planets Theodore Jacobson Observatory University of Washington Brian Stephanik October 5 th, 2005

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 1 st grader invites friends 5 th grader must move out to balance 5 th 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 –Monitor 1,000,000 nearby stars –Tens of thousands of new ESPs possible

Thank you  Questions?