Astronomy Chapter 9 Flashcards

Questions and Answers

The objects that are sometimes visible in the night sky with long tails are __________.

comets

Leftover planetesimals that formed in the region of the solar system now occupied by the jovian planets are called _________.

asteroids

Pieces of asteroids that have fallen to Earth are called ___________.

meteorites

Leftover planetesimals that formed inside the frost line are known as ___________.

dwarf planets Signup and view all the answers

Ceres, Pluto, and Eris are all round in shape and classified as ________.

dwarf planets Signup and view all the answers

Meteor showers are associated with debris from ________.

comets Signup and view all the answers

Why didn't a planet form in the region of the solar system now occupied by the asteroid belt?

Orbital resonances with Jupiter disrupted orbits in this region. Signup and view all the answers

The biggest surprise from the New Horizons flyby of Pluto was learning that Pluto ________.

shows clear evidence of recent or ongoing geological activity Signup and view all the answers

Rank these objects from left to right based on their distance from the Sun, from closest to farthest: a typical Oort cloud object, a typical asteroid in the asteroid belt, a typical Kuiper belt.

a typical asteroid in the asteroid belt, a typical Kuiper belt, a typical Oort cloud object Signup and view all the answers

Rank these objects from left to right based on their orbital period around the Sun from shortest to longest: a typical Oort cloud object, a typical asteroid in the asteroid belt, a typical Kuiper belt.

a typical asteroid in the asteroid belt, a typical Oort cloud object, a typical Kuiper belt object Signup and view all the answers

Rank these objects based on the distance from the Sun at which they are presumed to have formed, from nearest to farthest.

a typical asteroid in the asteroid belt, a typical Oort cloud object, a typical Kuiper belt object Signup and view all the answers

Rank the positions of the comet from left to right based on the expected size of its tail, from shortest to longest.

Positions depend on the comet's distance from the Sun. Signup and view all the answers

Match the following characteristics to comets, meteors, and asteroids.

Comets = most are located either in Kuiper belt or Oort cloud Meteors = dust particles entering Earth's atmosphere at high speed Asteroids = typically orbit the Sun at approximately 3 AU Signup and view all the answers

A comet entering the inner solar system from afar will __________.

form a coma and some time later form a tail. Signup and view all the answers

During the time that a comet passes through the inner solar system, the comet can appear quite bright because __________.

sunlight reflects off the comet's tail and coma Signup and view all the answers

A comet's plasma tail always points directly away from the Sun because __________.

of pressure exerted by the fast-moving charged particles in the solar wind Signup and view all the answers

About a trillion comets are thought to be located far, far beyond Pluto in the ________.

Oort cloud Signup and view all the answers

The bright spherical part of a comet observed when it is close to the Sun is the ______.

coma Signup and view all the answers

A comet's ____________ stretches directly away from the Sun.

plasma tail Signup and view all the answers

A comet's ________ is the frozen portion of a comet.

nucleus Signup and view all the answers

Particles ejected from a comet can cause a(n)_________on Earth.

meteor shower Signup and view all the answers

The__________extends from about beyond the orbit of Neptune to about twice the distance of Neptune from the Sun.

Kuiper belt Signup and view all the answers

According to this graph, the minimum size of an object that could cause a mass extinction is a little less than ____.

10 km Signup and view all the answers

According to the graph, an object 10 kilometers across hits Earth __________.

about once every 100 million years Signup and view all the answers

What is the probability that an object 100 meters in diameter will hit Earth during the coming year?

about 1 in 1000 Signup and view all the answers

Based on this graph, which statement below most accurately describes the impacts we should expect on Earth during the coming year?

Earth will be hit by at least one object a few meters in diameter, along with many smaller objects. Signup and view all the answers

The impact of a 100-meter object will not cause 'widespread' devastation, but it could still kill millions of people if it struck a major city. In Part C, you found that the probability of such an impact in any single year is only 1 in 1000. Suppose we learn that it has already been 1200 years since the last such impact. What would that tell us?

Nothing; we would still presume that the chance of such an impact during the next year is 1 in 1000. Signup and view all the answers

The asteroid belt lies between the orbits of:

Mars and Jupiter. Signup and view all the answers

Jupiter nudges the asteroids through the influence of:

orbital resonances. Signup and view all the answers

Can an asteroid be pure metal?

Yes, it must have been the core of a shattered asteroid. Signup and view all the answers

Did a large terrestrial planet ever form in the region of the asteroid belt?

No, because Jupiter prevented one from accreting. Signup and view all the answers

How big an object causes a typical shooting star?

a grain of sand or a small pebble Signup and view all the answers

About how often does a 1-kilometer object strike the Earth?

every million years Signup and view all the answers

What would happen if a 1-kilometer object struck the Earth?

It would cause widespread devastation and climate change. Signup and view all the answers

Which have the most elliptical and tilted orbits?

Oort cloud comets Signup and view all the answers

Which are thought to have formed farthest from the Sun?

Kuiper belt comets Signup and view all the answers

Choose the approximate time it would take for Earth to get 0.1% heavier at this rate.

10^14 years Signup and view all the answers

Is this mass accumulation significant for Earth as a planet?

This extra mass is unimportant compared to Earth's existing mass. Signup and view all the answers

What does Pluto most resemble?

a comet Signup and view all the answers

Which of the following statements about asteroids, Kuiper belt objects, and Oort cloud objects is true?

Objects in the asteroid belt and Kuiper belt orbit the Sun in nearly the same plane as the planets, but objects in the Oort cloud do not. Signup and view all the answers

Estimate Comet Tempel 1's diameter, using the scale bar in (Figure 2). Express your answer to one significant figure and include the appropriate units.

d = 5 km Signup and view all the answers

According to the graph in (Figure 1), how frequently do objects the size of Comet Tempel 1 strike Earth?

about once every hundred million years Signup and view all the answers

Consider an object twice the size of Comet Tempel 1. What kind of damage would this object cause if it hit our planet?

mass extinction Signup and view all the answers

The Meteor Crater in Arizona is about 1.2 kilometers across. According to the graph, about how big was the object that made this crater?

100 meters Signup and view all the answers

How often do objects big enough to create craters like the Meteor Crater impact Earth?

about once every ten thousand years Signup and view all the answers

What is the significance of the impact described in this article?

It was the first time astronomers tracked an asteroid before it hit Earth. Signup and view all the answers

What does an asteroid impact probability of 99% mean?

It means there is a 1% chance the asteroid will miss Earth. Signup and view all the answers

If Earth had no atmosphere, how would the asteroid's kinetic energy shortly before it impacted the surface compare to its kinetic energy when it was far away from Earth?

It would hit the surface with much higher kinetic energy than it had when it was far away. Signup and view all the answers

Where did the energy of impact come from?

The kinetic energy of the asteroid was transformed by friction into heat while it passed through the Earth's atmosphere. Signup and view all the answers

Which statement is NOT thought to be true of all comets in our solar system?

Comets always have tails. Signup and view all the answers

Which direction do a comet's dust and plasma tails point?

generally away from the Sun Signup and view all the answers

When a comet passes near the Sun, part of it takes on the appearance of a large, bright ball from which the tail extends. This part is called _________.

the coma Signup and view all the answers

A rock found on Earth that crashed down from space is called _________.

a meteorite Signup and view all the answers

The asteroid belt is located _________.

between the orbits of Mars and Jupiter Signup and view all the answers

A typical meteor is created by a particle about the size of a _________.

pea Signup and view all the answers

Among discovered meteorites, we have found some with all the following origins EXCEPT _________.

being a fragment from Comet Halley Signup and view all the answers

Study Notes

Celestial Objects

Comets: Visible with long tails when near the Sun, forming a coma and subsequently a tail as they approach.
Asteroids: Leftover planetesimals from the solar system's formation, primarily found between Mars and Jupiter in the asteroid belt.
Dwarf Planets: Ceres, Pluto, and Eris are round and classified as dwarf planets.
Meteorites: Solid debris of asteroids that fall to Earth, causing meteor showers when they enter the atmosphere.

Formation and Characteristics

Objects closer to the Sun are primarily rocky, while those in the outer regions, like the Kuiper belt and Oort cloud, are more icy.
The Oort cloud is believed to contain about a trillion comets, formed in the region of the jovian planets and later ejected to their current orbits.
Orbital resonances with Jupiter disrupted the formation of planets in the region now occupied by the asteroid belt.

Comet Dynamics

A comet’s tail varies in length based on its proximity to the Sun, being longer when close and shorter when distant.
The plasma tail of a comet always points away from the Sun due to solar wind pressure.
The coma is the bright spherical part of a comet comprising gas and dust.

Impact Events

An object about 10 km in diameter can statistically cause mass extinction events.
A 1 km object strikes Earth approximately every million years and can cause widespread devastation.
Meteor impacts are more frequent for smaller objects, with those around 100 meters striking about every 100,000 years.

Astronomical Statistics

A 100-meter asteroid can still kill millions if it impacts a populated area, despite a 1 in 1000 chance per year of such an event occurring.
Predictions and models suggest future predictions remain stable despite time without recorded impacts, maintaining the likelihood as unchanged.

Properties of Meteorites and Asteroids

Asteroids can be composed entirely of metal if formed from the core of a shattered body.
The unique properties of Oort cloud comets include the most elliptical and tilted orbits, compared to asteroids and Kuiper belt objects, which orbit in a similar plane to the planets.

Effects of the Atmosphere on Impacts

Without an atmosphere, a meteor’s kinetic energy increases significantly upon impact due to gravitational acceleration.
Kinetic energy transformed into heat upon impact can result from atmospheric friction during entry.

General Knowledge

Not all comets create tails; tails are visible only when comets approach the Sun.
A typical meteor results from particles as small as a pea entering the Earth's atmosphere.
The asteroid belt is situated specifically between the orbits of Mars and Jupiter.

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Description

Test your knowledge on celestial objects in this Chapter 9 flashcard set from your astronomy course. Learn about asteroids, comets, dwarf planets, and meteorites and their significance in our solar system. Perfect for reviewing key terms and concepts before your exam.