12 Formation of Planetary Systems Flashcards
What is a Protoplanetary disc?
A Protoplanetary disc is a rotating disk of dense gas and dust surrounding a newly formed star
What is a frost line?
A frost line marked the boundary beyond which it was cold enough for volatiles to freeze onto tiny particles of dust; within the frost line, only metals and rock could condense into solid grains
How did the planets form?
Accretion
What is accretion?
Accretion is when small grains of solid material collide and stick into each other forming larger flakes. These collide into other pieces forming larger and larger bodies.
How long did it take before the accreted pieces formed the cores of planets?
After ~100 million years, the accumulated pieces formed the metallic and silicate cores of the planets
What happened to the bodies beyond the frost line?
Beyond the frost lines, the cores of the protoplanets grew to much bigger sizes due to the large abundance of ices. The gravitational attraction of these massive cores were able to draw in large amounts of hydrogen and helium that were present in the outer solar system to form the atmospheres of four gas giant planets
What factors affect the presence of an atmosphere?
A planet’s or moon’s mass
Temperature
Magnetic Field
How does temperature affect the presence of an atmosphere?
The hotter the temperature, the faster the gas molecules move, making them more likely to escape the gravitational attraction of the planet or moon
How does a planet’s mass affect the presence of an atmosphere?
The greater the mass, the greater the gravitational pull on the atmosphere
How many bodies were there estimated to be in the early solar system?
50 bodies
Why are there only 8 bodies currently in the Solar System?
The 50 bodies collided, broke apart and re-formed a significant number of times before becoming an ordered system with stable orbits around the Sun
How is Mercury evidence for previous collisions?
Mercury’s iron core occupies over 60% of its volume; the planet is thought to have lost most of its rocky interior due to a collision with a protoplanet about one sixth of its size
How does axis tilts provide evidence for previous collisions?
The backwards spin of Venus and sideways spin of Uranus suggests that these two planets had significant collisions during the Solar System’s history
What is tidal heating?
Tidal heating is when internal friction and the interior of a Moon becomes warm
What happens during tidal heating?
Thermal energy is produced at the expense of rotational kinetic energy, and the moon’s spins slows down a little. Over time, this results in a synchronised rotation where the Moon’s rotational and orbital period are the same
How is energy transferred during tidal heating?
The Internal friction produces energy which heats up the moon
What happens when the moon’s rotation becomes synchronised with it’s orbit?
Tidal heating doesn’t end because most moon orbits aren’t perfectly circular: A varying orbital speed means that tidal bulges still occur and oscillate about a mean position
What is the orbital interaction between various bodies called?
Orbital Resonance
How does orbital resonance work?
Orbital Resonance works when the different moons are aligned and and ‘tugged’ out of shape meaning they don’t have circular orbits
What is tidal heating responsible for?
Tidal heating is responsible for the molten layers that are beneath the rocky or icy crusts of large moons. This is responsible for active volcanoes or cryovolcanoes (ice volcanoes)
What happens if a moon’s elastic forces aren’t strong enough?
If a moon’s internal elastic forces that resist deformation aren’t strong enough, the tidal forces will break up the body or prevent one from forming
How are planetary rings formed?
Planetary rings are believed to be formed after a moon was broken up by tidal forces and the fragments spread around the planet
What is the Roche Limit?
The Roche limit is the minimum distance a large satellite can approach its parent body without being torn apart
What are the Lagrangian points?
The Lagrangian points are the stable positions near large objects in orbit. These are the points where a small object is able to orbit
How can a Satellite be stable in the Lagrangian points?
The Lagrangian points in a two body system (an example is the Earth and Sun) at which their combined force of gravity is equal to the centripetal force needed to maintain the circular motion of a third object (a satellite)
What are Exoplanets?
Exoplanets are planets that orbit a star outside the Solar System
What observation methods of stars can you use to discover exoplanets?
- Astrometry
- Transit Method
- Radial Velocity Method
What is Astrometry?
Astrometry is when massive Exoplanets orbit their star and their combined gravitational pull can cause the star to move or wobble slightly in its position around the common centre of gravity
What is the Transit Method?
The Transit Method is when you can detect an Exoplanet transiting across the host star. This causes a very small (1%) drop in brightness for the duration of their transit.
What is the Radial Velocity Method?
The radial velocity method is when the slight wobbling of a star due to orbital motion of the exoplanet can be detected as small Doppler-shifts in the wavelengths of the the star’s spectral lines as it moves in the line-of-sight of the observer.
How do astronomers carry out the Radial Velocity method?
Astronomers uses spectroscopy to reveal small changes in a stars spectral lines.
What method is the most effective for detecting exoplanets?
The Radial Velocity Method
What are the two chemicals that are essential for the creation of life?
Carbon and Water
Why is Carbon essential for the creation of life?
Carbon has the ability to make interesting compounds such as amino acids and can form more complex organic molecules
Why is Water essential for the creation of life?
Water in its liquid form is an excellent solvent and acts as a transport mechanism for many nutrients
What is the Habitable (Goldilocks) Zone?
The Habitable Zone is the area a planet must be if liquid water is to be located on its surface
What is the Drake Equation?
The Drake Equation is the equation that attempts to estimate the likelihood of intelligent life in our galaxy
Which three moon’s in the solar system do astronomers believe could have primitive life?
Saturn’s Moon Titan
Jupiter’s moon Europa
Saturn’s moon Enceladus
Why could Saturn’s moon Titan support life?
Saturn’s moon titan has seas of liquid hydrocarbons
Why could Jupiter’s moon Europa support life?
Jupiter’s moon Europa contains an ocean of liquid water under its outer shell
Why could Saturn’s moon Enceladus support life?
Saturn’s moon Enceladus has eruptions of salt water, hydrocarbons and carbon
What does SETI stand for?
Search for Extraterrestrial Intelligence
What types of waves are used for SETI?
Radio
What are the factors of the Drake Equation?
Number of Stars in our galaxy
Number of earth-like planets in the Habitable zone
Fraction of stars with orbiting planets
Fraction of Earth-like planets on which life evolves
Fraction of Planet’s life for which intelligent civilisations live
Fraction of planets where life is intelligent and develops technology to communicate with us
What are extremophiles?
Extremophiles are life forms that can live in extreme temperatures, conditions, high pressure and high concentrations of salt water
How many exoplanets systems are currently known?
> 200
How can you estimate the diameter of an exoplanet?
diameter = speed × time interval of beginning a transit to being fully in the disk of the parent star
Which planet in the Solar System has the largest mass?
Jupiter
Which planet in the Solar system has the lowest density?
Saturn
Which Planet orbits closest to the Kuiper belt?
Neptune
What is the approximate distance to the Oort Cloud?
2 l.y.
What shape can the orbits of long-period comets be?
Elliptical and parabolic
How could water have come to Earth?
Deposits by comets and large asteroids
What are the classes of meteorites?
Iron
Stone
Stoney-Iron
What are the two most common elements in an iron meteorite?
Iron and Nickel
Where is it believed that iron meteorites originate?
The cores of asteroids
What are the two most common elements in a stone meteorite?
Oxygen and Silicon
Give examples of 4 large scale collisions in the Solar System.
- Giant Impact Hypothesis which formed the Moon
- Uranus’ sideways spin
- Venus’ backwards spin
- Impact craters on the Moon, Mars and asteroids
- Large Iron Core of Mercury
How are grooves formed on Mars’ moon Phobos?
Rocky Matter was ejected from Mars following a collision with a large meteoroid
Which 2 Moons were caused by gravitational capture?
Mars’ Deimos and Phobos
What are the causes of Mars’ lack of atmosphere?
After Mars’ formation, Mars probably has a molten core in which electric currents could flow and produce a magnetic field.
Mars’ magnetic field was able to deflect particles of solar wind around the planet.
As Mars cooled, its molten core solidified and currents could no longer flow meaning the Magnetic field was lost
The solar wind was no longer deflected so blew away particles in Mars’ atmosphere
How is Enceladus responsible for Saturn’s E-ring?
Water and ice is ejected from Enceladus’ geysers. Some water and ice falls back onto Enceladus and some is captured by the gravitational field of Saturn forming its E-ring.
What is the smallest astronomical body in the Solar system that is spherical?
Mimas (One of Saturn’s moon)
What are the opposing factors that an astronomical object depends on to be spherical or not?
Gravitation and Elastic
How can a moon be unaffected by tidal forces?
The moon could have a small diameter and/or the distance between the moon and its parent planet is large
Why is it more likely for planets with large diameters to be broken up by Tidal forces when the come closer than a planet’s Roche Limit?
Tidal forces are gravitational in origin. Gravity follows an inverse square law.
The moon must have a large enough diameter for the difference in gravitational pull on the ‘near’ and ‘far’ side of the moon to be significant/greater than elastic forces
Why do the Gas giants have larger cores compared to the rocky planets?
For our Solar System, the Frost Line was about 5 AU from the Sun. Within the frost line, volatile ices were unable to condense due to the high temperatures. However, beyond the Frost Line, it was cold enough for ices to condense and these are thought to have caused the significantly larger cores of the gas giants.
Why is there an absence of hydrogen and helium in the Inner Solar System compared to the Outer Solar system and gas giants?
Solar wind is most likely reason for ‘blowing’ light gases toward the Outer Solar system.
Solar wind is ‘strongest’ closer to the Sun i.e. in the inner Solar System
