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Astronomy 2201B > Chapter 7 > Flashcards

Chapter 7 Flashcards

1
Q

Near Earth minor planets populate what region of the SS?

A

Inner Solar System

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2
Q

Main belt minor planets populate what region of the SS?

A

The middle

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3
Q

What is the outer region of the SS populated with?

A

Comets, plutinos, TNOs, and Scattered Disk objects

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4
Q

Where is the asteroid belt located?

A

Between inner (terrestrial) planets and outer (Jovian) planets

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5
Q

What does the asteroid belt contain?

A

The orbits of all inner SS planetesimals not incorporated into a planet

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6
Q

What is the approximate mass of the asteroid belt?

A

Approx. 5x10^21 kg (1/3 of Pluto)

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7
Q

What is the name of the largest asteroid and what is its mass/diameter?

A

Ceres, Diameter: 940km, Mass: 10^21 kg

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8
Q

What is special about Ceres?

A

It is the only dwarf planet in the asteroid belt

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9
Q

Why is there no planet in the asteroid belt region?

A

Because of Jupiter’s perturbations

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10
Q

Can asteroids have their own moons?

A

Yes

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11
Q

What is mean motion resonance in regards to the asteroid belt?

A

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.)

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12
Q

What is mean-motion resonance dependent on?

A

Only the size (average distance form the Sun) of an objects orbit, not its mass.

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13
Q

What are the 2 groups of asteroids stabilized by mean-motion resonance from Jupiter?

A

Hilda (3:2) and Trojan (1:1) groups

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14
Q

What are the 4 major asteroid families?

A

Eos, Hirayama, Themis, Kornois (ojects in grops show similar spectra)

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15
Q

What is a Larange Point?

A

Where Jupiter’s orbit intersects 2 groups of Trojan asteroids (about 120 degrees from each other)

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16
Q

How are asteroid families created?

A

When an asteroid undergoes a collision, it produces fragments which stay near its orbit

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17
Q

How do smaller asteroids escape the belt?

A

Via resonance and solar radiation pressure over long periods of time

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18
Q

What are the 4 classes of NEAs and how do their orbits correspond with Earth’s?

A

Amor (outside), Apollo (fully crosses), Aten (crosses only near aphelion), Atira (inside)

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19
Q

What is the minimum orbital distance from Earth’s orbit for a Potentially Hazardous Asteroid?

A

<0.05AU

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20
Q

When larger asteroids prodice fragments, what are the 2 ways they behave?

A

Either has post-collsional resonance or evolve to a major resonance “escape” hatch

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21
Q

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”?

A

The Yarovsky Effect

22
Q

What may occur after the Yarvosky Effect takes place?

A

The asteroid may be sent into resonance and escape from the asteroid belt

23
Q

What is the relationship between diameter and number of bodies of that diameter in the asteroid belt?

A

N=1/D^2

24
Q

What is the usual way of determining an asteroid’s size?

A

Assume a sphere and an albedo of 10%, measure brightness (telescope) and determine distance (orbit), can find geometrical surface area

25
Q

What is albedo?

A

The fraction of incident light that is reflected

26
Q

What is the density of asteroids compared to meteroites?

A

The “rubble-pile” (large fragments and small debris) make-up leads to lower density than meteroites

27
Q

How are asteroid classes established?

A

Based on their spectra

28
Q

What does the spectra of an asteroid indicate?

A

The minerals present on the surface ONLY

29
Q

How many major classes of asteroids are there?

A

16 classes

30
Q

What are the 2 main sources of thermal energy in an asteroid?

A

Collisions (primordial and recent) and radioactivitiy

31
Q

What is the difference between comets and asteroids?

A

Comets are cold, dusty, volatile/ice-rich; asteroids are rocky, volatile-poor

32
Q

How large is a comet nuclei?

A

Approx 10-20km in diameter

33
Q

Are comets single bodies or bound rubble piles?

A

Can be both

34
Q

How close to the Sun must a comet before it begins producing a tail?

A

Must be approx 3AU for ice to being vaporizing (sublimation temperature of water)

35
Q

How long is a comets tail and which direction does it always point?

A

Approx 10^8km long and always points away from the Sun

36
Q

What is the name of the cloud of gas around a comet when it is producing a tail and how large is it?

A

Called a coma, and it is typically 10^4-10^5km across (the further out they form the more volatile the material)

37
Q

Why are comets typically hard to detect?

A

Their orbits are highly elliptical, which means they are most often inactive

38
Q

What is a “dust crust”?

A

large non-voalite rock material that builds up as ice disappears

39
Q

Which comets have a dust crust?

A

Comets that have passed by the Sun many times and have dark (vs. white) surfaces

40
Q

What are long period comets?

A

Comets with an orbital period longer than 200 years, orbit extends out past planetary nebula (come from Oort Cloud)

41
Q

What are short period comets?

A

Comets with orbits less than 200 years, inclinations similar to planets’, come from Kuiper-belt (just outside Neptune’s orbit)

42
Q

How are comets removed from the Oort Cloud?

A

Can be slingshot by the perturbations of passing stars

43
Q

How large is the Oort cloud and what determines the edge?

A

The edge is approx 50,000 AU from Sun, defined by the edge of “stable” orbits

44
Q

How many 1km diamter or greater objects are located in the Oort Cloud?

A

Approx 10^12

45
Q

How are half of the SS comets ejected?

A

Their orbits are disturbed by planets while in perihelion

46
Q

How many comets make up the Kuiper Belt?

A

Approx 10^9-10^10

47
Q

Why dont these comets typically develop tail?

A

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)

48
Q

What are KBO with 3:2 resonance with Neptune? 2:1?

A

Plutinos (3:2), and Twotinos (2:1)

49
Q

What is the gas to dust ratio in a comet?

A

About 1 to 100

50
Q

What is a Dust Tail

A

A tail formed, separate from an gas tail, that is yellowish in colour

Astronomy 2201B (11 decks)

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