Chapter 13

Question 1

Exoplanet Types

Answer 1

• Terrestrial
• Neptune Like
• Super Earth
• Gas Giants

Question 2

Terrestrial Planets

Answer 2

• Earth sized or smaller
• Mostly made of rock/metal
• Some could have oceans/atmospheres/other signs of habitability

Question 3

Neptune-Like Planets

Answer 3

• Similar in size to our won Neptune/Uranus with H/He atmospheres
• “mini Neptunes” not found in our solar system (Smaller than Neptune but larger than Earth)

Question 4

Super-Earth Planets

Answer 4

• Typically “terrestrial”/rocky
• More massive than Earth but lighter than Neptune
• May/may not have atmospheres

Question 5

Gas Giant Planets

Answer 5

• The size of Saturn/Jupiter
• Includes “hot” Jupiter’s (scorching planets in close orbits to their stars)

Question 6

How did we learn that other stars are Suns?

Answer 6

• Ancient observers didn’t think that because our Sun is so much brighter
• Christian Huygens showed that stars like our Sun must be at great distances, consistent w the lack of observed parallax

Question 7

Direct Planet Detection

Answer 7

Pictures/Spectra of the planets themselves

Question 8

Indirect Planet Detection

Answer 8

Measurements of stellar properties revealing the effects of orbiting planets

Question 9

Solar System Center of Mass

Answer 9

• The Sun and Jupiter orbit around their common center of mass
• The Sun wobbles around this center
• Can be used to determine masses/orbits of all the planets

Question 10

Doppler Technique

Answer 10

Measuring a star’s Doppler shift can tell us its motion toward and away from us
Current techniques can measure motions as small as 1 m/s (walking speed!)

Question 11

How did we find the first Extrasolar Planet?

Answer 11

• Doppler shifts of the star 51 Pegasi indirectly revealed a planet with 4-day orbital period.
• This short period means that the planet has a small orbital distance.
• This was the first extrasolar planet to be discovered around a Sun-like star (1995)

Question 12

How can changes in a Stars brightness Reveal the Presence of planets?

Answer 12

• Planet Transits
• Eclipses
• No orbital tilt

Question 13

Planet Transits:

Answer 13

When a planet crosses in front of a star, resulting in a dip in brightness

Question 14

Planet Eclipse

Answer 14

Sometimes can be seen, when the planet passes behind the star

Question 15

Lack of Orbital Tilt

Answer 15

A way to accurately measurement of planet mass

Question 16

Kepler’s Mission

Answer 16

NASA’s Kepler mission was launched in 2008 to begin looking for transiting planets.

It is designed to measure the 0.008% decline in brightness when an Earth-mass planet eclipses a
Sun-like star.

It has found over 4000 planet candidates as of 2015.

Question 17

Gravitational Lensing

Answer 17

Mass bends light in a special way when a star with planets passes in front
of another star

Question 18

Features in Dist Disks

Answer 18

Gaps, waves, or ripples in disks of dusty gas around stars can indicate
presence of planets

Question 19

Measurable Properties in Stars/Planets

Answer 19

Orbital period, distance, and shape
Planet mass, size, and density Atmospheric properties

Question 20

What can a Doppler Shift tell us?

Answer 20

A planet’s mass and the shape of its
orbit

Question 21

Suppose you found a star with the same mass as the Sun moving back and forth with a period of 16 months. What could you conclude?

Answer 21

It has a planet orbiting at greater than 1 AU

Question 22

Direct Detection

Answer 22

Obtain images/spectra of extra-solar planets

Question 23

Astrometric method

Answer 23

Infer planet’s existence from small changes in the star’s position in sky

Question 24

Transit Method

Answer 24

Infer planet existence from slight changes in a star’s brightness as planet passes in front of/behind it

Question 25

Calculating Density

Answer 25

Using mass and size to determine density can be calculated

Question 26

Spectrum During Transit

Answer 26

Change in spectrum during a transit tells us about the composition of planet's atmosphere.

Question 27

Surface Temp Map

Answer 27

Measuring the change in infrared brightness during an eclipse enables us to map a planet's surface temperature.

Question 28

Orbits of Extra solar Panets

Answer 28

- Most have orbits smaller than Jupiter's - Greater the distance harder to use the Doppler technique - Orbits of some have a higher eccentricity than those in our solar system

Question 29

Planetary Migration

Answer 29

the process where a planet's orbital radius changes due to interactions with the surrounding material, like a protoplanetary disk or other planets

Question 30

Gravitational Encounters

Answer 30

Between two massive planets can eject one planet can eject one planet while flinging the other into a highly elliptical orbit.

Question 31

What happens in a gravitational encounter that allows a planet's orbit to move inward?

Answer 31

It transfers energy and angular momentum to another object.

Question 32

GAIA Mission

Answer 32

a European mission launched in 2013 that will use interferometry to measure precise motions of a billion stars