Exoplanets

1
Exoplanets
2
Distant Worlds

• Many stars have solar systems with exoplanets.
• Ideally we could see them with telescopes.
• Faint planets, cool infrared, must be very large
• A few systems have been seen with direct imaging.

Beta Pictoris
HR 6799
Keck Observatory
Gemini Observatory
3
Moving Source

• Light moves equally in all directions from a
  source.
• Circular (or spherical) pattern
• If the source is moving the origin also moves.

• The wavecrest separation changes with the
  observer.
• Shorter ahead
• Longer behind

4
Doppler Shift

• The wavelengths of light change from moving
  objects.
• Depends on velocity
• Shorter when approaching
• Longer when receding
• The change is called the Doppler shift.
• Redshift away
• Blueshift towards

Cornell University
5
Binary System

• A binary system has two objects bound by gravity.
• Small mass in orbit
• Large mass wobbles
• The wobbles cause velocity changes.
• Doppler shifts

Wikipedia
Max Planck Institute
6
Planetary Orbits

• The changes in the orbit of the star show the
  presence of a planet.

7
Doppler Success

• Many systems have been identified by Doppler
  shifts.
• Dark points on graph
• Most planets are large and close to the star.

MJ
ME
RE
RJ