A12 - Formation of planetary systems Flashcards
What is the centre of gravity called in a system?
barycentre
Name 3 effects of tidal gravitational forces:
Apart from ocean tides
ring systems - small body is held too closely and disintegrates (Roche Limit)
asteroid belts - eg the Asteroid Belt has enough material to form a small terrestrial planet but the tidal effects of Mars and Jupiter prevented it
internal heating
Explain the process of internal heating:
-over time, the planet’s gravity causes the moon’s rotation to slow down (eventually becoming tidally locked), and distorts its shape too
-the moon’s rotational kinetic energy decreases while its thermal energy increases, internally heating the moon
Why might the moons of Jupiter/Saturn have the capability of having liquid water inside it?
they generate internal heat due to tidal gravitational forces
Name 4 effects caused by the gravitational interactions of multiple bodies:
-gradual shifts in orbits
-chaotic motion
-orbital resonance
-Lagrangian points
What is orbital resonance?
where 2 or more bodies (orbiting another larger body) have a gravitational effect on one another in their orbit, so their orbital periods have a specific time ratio
eg Io, Europa, and Ganymede are in a ratio of 4:2:1
Describe what Lagrangian points are:
the locations relative to a body orbiting a larger body where the combined effects of gravity from both of them equal the centripetal force needed for another body to orbit with them around the larger body
L1/2/3 are unstable, L4 (60° ahead) and L5 (60° behind) are most stable
Centripetal force is a force that acts inwards, perpendicular to its motion, in order to maintain the object’s circular path
What are the objects found at Jupiter’s Lagrange points?
-asteroids which are collectively they are named the Trojans
-L4 (leading) contains the Greek Camp
-L5 (trailing) contains the Trojan Camp
Give some evidence that shows that Jupiter may have changed its position during the formation of the Solar System:
-formation of the asteroid belt
-quite far out compared to the position of similarly-sized planets in other planetary systems
What is the Roche Limit? Name 1 effect of it:
-the distance that a moon has to be from its parent body, such that going any closer would mean the gravitational forces would overcome the moon’s internal elastic forces, causing deformation and ripping the moon apart
-this would form a ring system around the parent body
Describe how a celestial body’s shape depends on its mass:
-smaller bodies with less mass don’t have enough gravity to overcome the elastic forces holding its irregular shape (eg asteroids)
-larger bodies have enough gravity to form a symmetrical oblate spheroid, a very stable shape
When it is a sphere/oblate spheroid, it is said to be in “hydrostatic equilibrium” (same name for stars)
Explain how a planet’s atmosphere might be unstable:
-if the mass of the planet is too low, it might not be able to hold on to the gases present
-if it is too hot or close to the Sun, the kinetic energy of the gas molecules could be high enough such that they could be ejected out higher than escape velocity
How did the gas giants form?
-formed behind the Frost Line (where gases can freeze into solids as the temp. is low enough)
-instead of rock accreting, gas accreted around the cores of the gas giants
-there was much more gas available so they became much bigger
Describe 3 methods of discovering exoplanets:
transit method - measured decrease in light intensity when the planet moves in front of its star
astrometry - measuring tiny wobbles in the star’s position, with respect to background stars, due to the gravitational pull of planets
radial velocity - measuring tiny wobbles back and forth, causing a slight red/blueshift
Describe how exoplanets can be discovered by plotting a light curve of a single star:
if the star shows regular dips in brightness in the light curve, it indicates the presence of an exoplanet that orbits the star and passes in front of the star regularly
Why might Titan be a good place for life to form?
-large nitrogen-rich atmosphere
-organic compounds found on its surface
-surface temperature is very low (-180°C) but ideal conditions may be found underground
Why might Europa be a good place for life to form?
has a large underground water ocean
Why might Enceladus be a good place for life to form?
spews out geysers of water from its South Pole
How do astronomers estimate the number of civilisations in the galaxy?
Drake Equation (proposed by Dr Frank Drake in 1960)
What is SETI, and what do they do?
-Search for Extra-Terrestrial Intelligence (an organisation)
-they have been “listening” for radio waves in parts of the galaxy that are likely to be able to support life
-they have also sent out radio waves too
eg the Arecibo message
