Topic 12

Question 1

Define the Goldilocks zone

Answer 1

region around star where liquid water might be found on surface of planet

Question 2

where is the goldilocks zone on smaller and more massive stars?

Answer 2

-further out from star (more massive stars)

-closer to star (smaller stars)
planets here are exposed to high x-ray levels

Question 3

What does SETI stand for

Answer 3

Search for Extra-Terrestrial Intelligence

Question 4

What kind of wave does SETI use

Answer 4

Radio-wave

Question 5

Define Exoplanet

Answer 5

a planet that orbits another star

Question 6

Name 4 methods of discovering exoplanets

Answer 6

1.The Transit Method
2.Astrometry
3.Radial Velocity Method
4.(Direct Imaging)

Question 7

Describe the transit method

Answer 7

-method used to discover exoplanets
-“wink”
-planet passes infront of star and blocks the light
-causes a dip in star’s brightness

Disadvantage: planet must orbit aligned with earth so that we can see its transit

Question 8

Describe Astrometry

Answer 8

-method used to discover exoplanets
-“wobble”
-planet’s gravity pulls star, causing it to wobble
-this method detects the wobble

Example:ESA’s Gaia Satellite

Question 9

Describe the Radial Velocity Method

Answer 9

-method used to discover exoplanets
-“wobble”
-planet’s gravity pulls star, causing it to wobble
-it’s red-shifted when it moves towards earth
-it’s blue-shifted when it moves away from earth

Question 10

Describe Direct Imaging

Answer 10

looks at the infrared radiation reflecting off the exoplanet

Question 11

When did most collisions occur

Answer 11

heavy bombardment period

Question 12

Give 4 pieces of evidence of collisions

Answer 12

1.Earth’s axial tilt (theia->moon)
2.Venus’ retrograde spin (not all scientists agree with this)
3.Uranus’ orbital tilt (80 degrees)
4.Impact craters on surface of moon (and earth) -(mimas which looks like death star)

Question 13

Define solar wind

Answer 13

-constant flow of charged protons & electrons from sun travelling at high speed (up to 400km/s)
-They escape gravity of sun because they have too much energy

Question 14

Give 1st effect of solar wind-a

Answer 14

1.aurora
-when particles that get caught in the Van Allen Belts caused by the Magnetosphere then move along these field lines toward the magnetic north and south poles and observers in these location witness aurorae.

Question 15

Give 2nd effect of solar wind-c

Answer 15

2.comets have tails
-As comets move nearer the sun the sun’s radiation is responsible for heating a comet and the solar wind particles will interact with the comet and form an ion tail which points away from the Sun.

Question 16

Give 3rd effect of solar wind-h

Answer 16

3.heliosphere
-cigar-shaped bubble surrounding solar system caused by solar wind. (cigar shaped because sun is orbiting galactic centre) 80-100 AU from sun

Question 17

Describe the composition of a gas giant

Answer 17

-thick hydrogen and helium atmosphere
-rocky core
-largest gas giants have an outer core of liquid metallic hydrogen which creates a strong magnetic field
-smallest gas giants have an outer core of molecular hydrogen and water-ammonia

-jupiter and saturn have clouds at the top of their atmosphere

Question 18

How did the gas giants form?

Answer 18

-formed quickly in early few million years of solar system
-sun heated up+started nuclear fusion
-solar wind evaporated gas from planetary disc
-gas clumped together due to gravity
-swept up by gas giants
-rocky material would not be evaporated

Question 19

What are the 3 conditions which determine whether a planet will have an atmosphere or not

Answer 19

-high enough gravitational field strength
-not too hot for gas to escape into space
-not exposed to strong solar wind (magnetic field strength)

Question 20

What 2 forces determine if an object is spherical?

Answer 20

elastic forces
vs
gravitational forces

Question 21

How does an object become spherical?

Answer 21

high gravitational forces means that (object has enough mass) so bits of surface fracture and flow round to be more round

-not enough mass= grav forces too low to be spherical

Question 22

Define Roche Limit

Answer 22

The distance from a planet where an orbiting object will be broken apart by tidal forces which overcome gravitational forces of object

-these remnants are thought to have created ring systems

Question 23

How far away is the roche limit from a planet

Answer 23

~2.5x the planets radius

Question 24

Define barycentre

Answer 24

centre of mass of both/all bodies in orbiting system (which those bodies orbit)

Question 25

Define orbital resonance

Answer 25

where two or more bodies orbiting another larger body have orbital periods that have a gravitational effect on one another so their orbital periods use a time ratio.

Question 26

Give 2/3 examples of orbital resonance:

Answer 26

1. Jupiter’s moons -Ganymede, Europa, Io in 4:2:1 ratio 2.Neptune and Pluto -in 3:2 ratio -stops them colliding? (3.) Jupiter and saturn -5:2

Question 27

What are langrangian points?

Answer 27

locations relative to two bodies where a smaller object can maintain a position in orbit.

Question 28

What and where are each lagrangian point (on earth)?

Answer 28

L1- between earth and sun -good for viewing sun -SOHO satellite L2- other side of planet than L1 -good for viewing galaxy -james webb telescope, GAIA L3- other side of sun to earth -no communication with earth L4&5- little bit ahead/behind earth’s orbit -jupiter’s trojan asteroids are here -most stable lagrangian points -STEREO observatories

Question 29

Why is the moon’s orbit getting 4cm farther every year?

Answer 29

The effects of tides is causing Earth to slow down which in turn causes the Moon to lose momentum and slow down, moving it further away. -moves away because it conserves angular momentum

Question 30

Why hasn’t the asteroid belt formed a planet?

Answer 30

-Although it has enough material to make a small terrestrial planet: -tidal effects of mars’ and jupiter’s orbits prevented anything larger than ceres forming

Question 31

How is internal heating caused?

Answer 31

moon gets stretched and squashed as it rotates causing the inside to heat -may cause moons to be volcanically active (for example Io of jupiter)

Question 32

What effect do tidal forces have on moon’s rotation

Answer 32

slowing down moon’s rotation (synchronous rotation where orbital period=rotational period)

Question 33

Describe composition of inner planets’ atmospheres +titan & pluto

Answer 33

MERCURY-Small, close to the Sun and so likely not to have been able to form an atmosphere VENUS-Closer to the Sun than Earth but maintains a thick carbon dioxide atmosphere. EARTH- Nitrogen/oxygen atmosphere. Within the habitable zone, magnetosphere protects against the solar wind. MARS-Further away, smaller body than Earth/Venus, thinner carbon dioxide atmosphere, no magnetosphere. TITAN-Nitrogen/methane atmosphere, one and a half times ticker than Earths. Thought to be produced by internal heating. PLUTO-Past the main planets it keeps a very thin nitrogen atmosphere despite being smaller than Mercury. Thought to be produced by internal heating.

Question 34

What does solar wind do to planets

Answer 34

-it strips off planets’ atmosphere if planet does not have a strong enough magnetic field (magnetosphere) and/or gravitational field