Chapter 14: Solar System Debris

Relatively small, predominantly rocky objects that orbit the Sun; 300 km across.

What are asteroids?

Most have somewhat eccentric orbits between Mars and Jupiter.

Between which two planets does the asteroid belt reside?

C-type

This asteroid type makes up 75% of asteroids, contains a large amount of carbon, are not reflective, and found in the inner part of the belt.

S-type

This asteroid type makes up 15% of asteroids, contains mostly silicate/rocky materials, are highly reflective, and found in the outer part of the belt.

M-type

This asteroid type makes up 10% of asteroids and contains mostly nickel and iron.

They’re representative of the early stages of the solar system due to their material composition not being altered.

What is the significance of studying asteroids?

Must have eccentricities > 0.4 and cross Earth’s orbit.

What are the requirements for an asteroid to be considered an Earth-crossing asteroid?

The closest asteroid that will approach us over the next century; it will pass at 30,000 km.

What is asteroid Apophis and why have scientists been concerned about it?

It’s possible; we can send probes to shift its orbit years or decades ahead of time.

Can we prevent an asteroid from hitting Earth? How much notice do we need?

Intentional impacts, gravity tractor, nuclear explosives

What are some asteroid deflecting methods that scientists are currently working on?

Asteroids that orbit at the distance of Jupiter at L4 and L5 points (60° ahead or behind it), which are stable.

What are the Trojan asteroids?

5 points in the solar system where objects can orbit synchronously with Jupiter.

What are Lagrangian points?

They do not create their own light (they shine reflected light from the Sun), have highly eccentric orbits, and when they approach the Sun they brighten and develop a tail.

What are the characteristics of a comet?

They are highly eccentric.

What is the orbit of a comet typically like?

Only a few km across, where most of mass is, during most of their orbit only frozen nucleus exists.

Describe the nucleus of a comet.

Forms when comet gets closer to Sun, heats up, and ice sublimes into gas; can be size of Saturn or Jupiter

Describe the coma of a comet.

Invisible, surrounds comet, stretches out over millions of km.

Describe the hydrogen envelope of a comet.

Grows as comet approaches Sun; can extend up to 1 AU.

Describe the tail of a comet.

Perihelion

The tail of a comet is the brightest at _________.

Ion tail

An approximately straight tail made up of ionized molecules.

Dust tail

A broad, diffuse, and gently curved tail made up of dust.

Solar winds from the Sun pushes the tails away from the Sun; dust tails lag behind because dust particles are harder for solar winds to push.

In what direction is the tail of a comet always pointing?

Discovered by Edmund Halley; most famous comet with a period of 76 years. Last appeared in 1986 and will appear again in 2061.

What is Halley’s coment?

Short-period comets

This comet type has a period duration of 200 or less years and originates from the Kuiper Belt.

Long-term comets

This comet type has a period duration of hundreds of thousands or millions of years and originates in the Oort Cloud.

To explain the irregularities in the orbits of Uranus and Neptune; later found that Pluto had no affect on their orbits because it was not massive enough.

Why did Percival Lowell begin to search for another planet?

Clyde Tombaugh; March 13, 1930 (Lowell’s birthday)

Lowell searched for this “planet” until he died in 1916. Who discovered it after he passed and when was the discovery announced to the world?

Elongated, eccentricity of 0.25, it’s 29.7 AU from Sun at perihelion and 49.3 AU at aphelion, orbital plane is 17.2°, not aligned on ecliptic plane like other planets.

Describe the characteristics of Pluto’s orbit.

Charon

What is the name of Pluto’s largest moon?

5 (Charon, Nix, Hydra, Kerberos, Styx)

How many moons does Pluto have in total?

Water ice

Pluto and Charon both have densities of about 2100 kg/m³, which implies that they are mostly made up of what?

Objects that orbit the Sun at a greater average distance than Neptune does.

There are over 3,000 trans-Neptunian objects, which are what?

Kuiper Belt

Most of these objects are _________ objects, which are objects that orbit specifically in the Kuiper Belt, which resides between 30 and 50 AUs from the Sun

Pluto was not very different from all of the small bodies in the solar system.

The discovery of more and more trans-Neptunian objects made what clear about Pluto?

Farout or Eris

What is currently the most distant object ever observed in our solar system?

It orbits the sun, its massive enough that its gravity has caused its shape to be approximately spherical, and it has “cleared its neighborhood” around its orbit of other bodies.

A body is considered a planet if:

It has not “cleared its neighborhood” orbits in a belt of debris.

Which of these criteria does Pluto not satisfy?

Pluto can be closer to the Sun than Neptune; they won’t collide because of their 3:2 orbital resonance.

What’s the physical relationship between Pluto and Neptune?

The icy dwarfs planets beyond Neptune.

What are Plutoids?

Dwarf planet

The International Astronomical Union (IAU) invented a new term for objects that satisfy criteria 1 and 2 but not 3:

Eris, Pluto, Makemake, Haumea, and Ceres

What are the names of the five dwarf planets currently recognized by the IAU?

How science is constantly changing.

Pluto’s reclassification is an example of what?

The first asteroids, which were initially classified as planets.

The discovery of Pluto is similar to the discovery of what?

A sudden streak of light in the night sky caused by friction between air molecules in Earth’s atmosphere and an incoming piece interplanetary matter (asteroid, comet, or a meteoroid).

What is a meteor?

A small, rocky, or metallic body in space, smaller than an asteroid.

What is a meteoroid?

Has to do with size; meteoroids are smaller (< 100 m wide)

What is the difference between an asteroid and a meteoroid?

Any piece of interplanetary debris that reaches Earth’s surface.

What is a meteorite?

When Earth passes through left over debris from disintegrating short period comets as they make their way around the Sun.

What is the cause of a meteor shower?

The constellation from which the meteor showers appear to come from.

Meteor shows are named after what?

iron and metallic

Most meteorites are rocky but some are ___________.

old

Almost all meteorites are very _____.

They provide essential clues to the original state of matter in the solar neighborhood and what it formed from.

What is the significance of studying meteorites?

It is more inclined to the ecliptic plane than any of the eight planets.

What is so unusual about Pluto’s orbit?

Micrometeorites

Which solar system object disappear along the orbit?

Fireballs

Craters that hit Earth and are also meteoroids: