Lecture 10
Extrasolar planets: detection methods, characteristics
Thursday July 17, 2008
We examined the various methods of detecting extrasolar planets and discussed the implications of finding so many "hot Jupiters" to date. Powerpoint on Angel. Here are some useful animations of finding extrasolar planets via the Doppler and transit methods.
Concepts:
- Doppler method: Measure radial velocity shifts in star spectrum, find period and mass of planet
- Transit method: Measure slight dimming in light from star when planet crosses in front
- Gravitational microlensing: Planet can slightly bend light from background star, enhancing its brightness
- Pulsar timing: Planet can cause regular deviations from extremely consistent pattern of star pulses
Vocabulary:
- Hot Jupiters: Jupiter-like planets that orbit very close to their parent star (have short periods)
- Selection effect: Observe results that depend on method of measuring, don't necessarily reflect population as a whole
- Habitable zone: distance from star at which water can remain liquid; depends on type (temperature) of star
Activity:
We measured the Doppler shifts in velocity in the spectrum of a star, figured out the period and the maximum velocity, and calculated the distance and mass of the planet. The (faked) data were created to correspond to HD 209458b, a planet with a period of only 3.5 days (so orbiting at 1/8 the radius of Mercury's orbit) but a mass of 0.7 times Jupiter (220 times Earth). This planet also transits its star, enabling scientists to understand its composition. It is losing atmosphere in a large tail as it orbits.
Random link:
Excerpt from Calgary Herald article titled "Space trip fished from garbage"
A French air hostess will become one of Europe's first space tourists after picking a chocolate wrapper out of the garbage and finding a winning number in a contest to fly to the upper reaches of Earth's atmosphere.
Mathilde Epron, 32, said she bought a Kit Kat bar at her local supermarket but initially threw the wrapper away, telling herself "it's only others who win." Two hours later, thinking back to the competition, she decided to try her luck and fished the wrapper out of the garbage, only to find a code marked inside.
Updated July 17, 2008