Chapter 7 Flashcards
Near Earth minor planets populate what region of the SS?
Inner Solar System
Main belt minor planets populate what region of the SS?
The middle
What is the outer region of the SS populated with?
Comets, plutinos, TNOs, and Scattered Disk objects
Where is the asteroid belt located?
Between inner (terrestrial) planets and outer (Jovian) planets
What does the asteroid belt contain?
The orbits of all inner SS planetesimals not incorporated into a planet
What is the approximate mass of the asteroid belt?
Approx. 5x10^21 kg (1/3 of Pluto)
What is the name of the largest asteroid and what is its mass/diameter?
Ceres, Diameter: 940km, Mass: 10^21 kg
What is special about Ceres?
It is the only dwarf planet in the asteroid belt
Why is there no planet in the asteroid belt region?
Because of Jupiter’s perturbations
Can asteroids have their own moons?
Yes
What is mean motion resonance in regards to the asteroid belt?
There occurs gaps in the distibution of the asteroid belt at locations where an objects orbit time is a small integer of Jupiter’s (ex. 3:2, 2:1 etc.)
What is mean-motion resonance dependent on?
Only the size (average distance form the Sun) of an objects orbit, not its mass.
What are the 2 groups of asteroids stabilized by mean-motion resonance from Jupiter?
Hilda (3:2) and Trojan (1:1) groups
What are the 4 major asteroid families?
Eos, Hirayama, Themis, Kornois (ojects in grops show similar spectra)
What is a Larange Point?
Where Jupiter’s orbit intersects 2 groups of Trojan asteroids (about 120 degrees from each other)
How are asteroid families created?
When an asteroid undergoes a collision, it produces fragments which stay near its orbit
How do smaller asteroids escape the belt?
Via resonance and solar radiation pressure over long periods of time
What are the 4 classes of NEAs and how do their orbits correspond with Earth’s?
Amor (outside), Apollo (fully crosses), Aten (crosses only near aphelion), Atira (inside)
What is the minimum orbital distance from Earth’s orbit for a Potentially Hazardous Asteroid?
<0.05AU
When larger asteroids prodice fragments, what are the 2 ways they behave?
Either has post-collsional resonance or evolve to a major resonance “escape” hatch
What is the name of the effect in which “asymetrical re-radiation of thermal energy for a rotating body can produce a small force that slowly changes its orbit over time”?
The Yarovsky Effect
What may occur after the Yarvosky Effect takes place?
The asteroid may be sent into resonance and escape from the asteroid belt
What is the relationship between diameter and number of bodies of that diameter in the asteroid belt?
N=1/D^2
What is the usual way of determining an asteroid’s size?
Assume a sphere and an albedo of 10%, measure brightness (telescope) and determine distance (orbit), can find geometrical surface area
What is albedo?
The fraction of incident light that is reflected
What is the density of asteroids compared to meteroites?
The “rubble-pile” (large fragments and small debris) make-up leads to lower density than meteroites
How are asteroid classes established?
Based on their spectra
What does the spectra of an asteroid indicate?
The minerals present on the surface ONLY
How many major classes of asteroids are there?
16 classes
What are the 2 main sources of thermal energy in an asteroid?
Collisions (primordial and recent) and radioactivitiy
What is the difference between comets and asteroids?
Comets are cold, dusty, volatile/ice-rich; asteroids are rocky, volatile-poor
How large is a comet nuclei?
Approx 10-20km in diameter
Are comets single bodies or bound rubble piles?
Can be both
How close to the Sun must a comet before it begins producing a tail?
Must be approx 3AU for ice to being vaporizing (sublimation temperature of water)
How long is a comets tail and which direction does it always point?
Approx 10^8km long and always points away from the Sun
What is the name of the cloud of gas around a comet when it is producing a tail and how large is it?
Called a coma, and it is typically 10^4-10^5km across (the further out they form the more volatile the material)
Why are comets typically hard to detect?
Their orbits are highly elliptical, which means they are most often inactive
What is a “dust crust”?
large non-voalite rock material that builds up as ice disappears
Which comets have a dust crust?
Comets that have passed by the Sun many times and have dark (vs. white) surfaces
What are long period comets?
Comets with an orbital period longer than 200 years, orbit extends out past planetary nebula (come from Oort Cloud)
What are short period comets?
Comets with orbits less than 200 years, inclinations similar to planets’, come from Kuiper-belt (just outside Neptune’s orbit)
How are comets removed from the Oort Cloud?
Can be slingshot by the perturbations of passing stars
How large is the Oort cloud and what determines the edge?
The edge is approx 50,000 AU from Sun, defined by the edge of “stable” orbits
How many 1km diamter or greater objects are located in the Oort Cloud?
Approx 10^12
How are half of the SS comets ejected?
Their orbits are disturbed by planets while in perihelion
How many comets make up the Kuiper Belt?
Approx 10^9-10^10
Why dont these comets typically develop tail?
Their orbits have low eccentricity, therefore are never brought too close to Sun (can be picked up by Neptune and sent into inner SS though)
What are KBO with 3:2 resonance with Neptune? 2:1?
Plutinos (3:2), and Twotinos (2:1)
What is the gas to dust ratio in a comet?
About 1 to 100
What is a Dust Tail
A tail formed, separate from an gas tail, that is yellowish in colour
