Planets
- Planets ~ 100-300 K peak at 10,000 to 30,000 nm
- cf. star’s peak near 500 nm
- NASA is working on infrared interferometers in space to directly detect planets
- “Terrestrial Planet Finder” Mission, part of the Origins theme
Look for planets indirectly
- Recall Newton’s laws of motion
- planet and star both orbit around common center of mass
- center of mass defined by teeter-totter balance
- For Sun-Jupiter, the c.o.m. is at the solar surface
- Therefore look for the reflex motion of the bright star
- velocity -- through Doppler shift
- position, star will wobble back and forth demo
- ~ 20 nearby stars show evidence for planets