Comets, Meteors, NEOS & PHOS

Question 1

What kind of orbits do comets have?

Answer 1

Highly elliptical.

Question 2

Describe the tail of a comet.

Answer 2

Points away from sun. Two types:

• Straight ion tail (Blue coloured, Fluorescence, Ionised carbon monoxide, Ionised by solar wind)
• Dust Tail (Lighter coloured, Broader, Curvier, Produced by radiation pressures pushing particles out of the nucleus, Reflects sunlight)

Question 3

Name two categories of comets.

Answer 3

Short period
< 200 years.
Originate from Kuiper Belt.
e.g. Halley’s comet.
Giotto probe 1986.

Long period
Originate fro Ort Cloud.
Paths clockwise or anticlockwise.
Orbits highly inclined to the ecliptic.
Originate vast distances from the sun.
e.g. Hale-Bopp.

Question 4

What is the Kuiper Belt?

Answer 4

• Where short period comets originate.
• Disc shaped region of icy bodies.
• Beyond Neptune.
• 30-50 AU from Sun.

Question 5

What is the Ort Cloud?

Answer 5

• Where long period comets originate.
• Spherical region of Cometary nuclei.
• Roughly 50,000 AU from sun.

Question 6

What is the difference between a meteoroid and a meteorite?

Answer 6

• A meteoroid is a small rocky irregular lump in the solar system. ( meteor -> meteorite

Question 7

Name three origins of meteoroids.

Answer 7

Broken fragments of colliding asteroids.
Impacts with the surface of the moon or Mars.
The dust tails of comets.

Question 8

How fast can a meteoroid’s orbit be?

Answer 8

40km/s

Question 9

What is a Meteoroid shower?

Answer 9

They can be a dramatic increase in the number of meteors observed when the earth passes through a meteoroid stream left by a comet.

Question 10

What causes meteors to appear as light streaks in the sky?

Answer 10

• When a Meteoroid enters the earth’s atmosphere it becomes a meteor.
• Friction between a meteor and the surrounding air produce heat and light and can be seen as light streaks in the night sky.

Question 11

What is a fireball?

Answer 11

Meteors with a bright magnitude of -3 or less.

Question 12

What is the radiant?

Answer 12

A point in the night sky from which meteors appear to diverge from.

Question 13

Describe the classification of meteorites.

Answer 13

• Stones
• Irons
• Stony Iron

Question 14

How do we name meteor showers?

Answer 14

Named after the constellation in which the radiant is found.

Question 15

Name 4 annual meteor showers and when they occur.

Answer 15

Perseids (August - in Perseus)
Leonids (January - in Leo)
Geminids (December - in Gemini)
Quadrantids (January - in Boötes)

Question 16

What is the definition of an NEO?

Answer 16

A near Earth object is an asteroid or comet who’s trajectory might bring them closer to earth than 0.3 AU

Question 17

What is a PHO?

Answer 17

A potentially hazardous object that has an orbit that brings them closer to earth than 0.05AU.

Question 18

Give examples of collisions between astronomical bodies in the solar system

Answer 18

• Craters (the moon, planets, earth)
• Unusual Rotations (Venus, Uranus)
• Comet Shoemaker-levy (collided with jupiter in July 1994)
• Tunguska Event (asteroid/comet explosion in Russia, 1908)

Question 19

Why do we need to monitor PHO’s?

Answer 19

An impact would have catastrophic consequences for life on Earth (especially if the PHO’s are larger than 1km)

Question 20

What is the Torino Scale?

Answer 20

The Torino Scale is a method for categorizing the impact hazard associated with NEOs
Scale from 0-10 (0=miss, 10=global disaster)