PHYS 107 Meteors, Asteroid, and Comets - BOLD ANSWERS

Meteors, Asteroid, and Comets

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1. You are standing outside at night and see a brief flash streak across the sky. You are looking at a

A)..Solar flare. B)..Aurora. C).. Moonbeam. D)..Comet. E)..Meteor.

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Animation of a Meteor Shower2. Why does a meteor glow?

A)...It is reflecting sunlight. B)... It is hot. C)...It is exciting the Earth's magnetic field. D)... It is reflecting the light of distant thunderstorms. E)...It is reflecting the light of distant cities.

3. How is a meteor's glow created?

A)... Its collision with molecules and atoms in our atmosphere heats it. B)...Radioactive atoms in are decaying. C)... Sunlight is heating the gases in its wake to thousands of degrees. D)... Its wake bends sunlight and refracts it into a narrow beam. E)... Hydrogen and oxygen atoms in the meteor combine and burn .

4. Where do meteors come from?

A)... Some are fragments of asteroids. B)... Some are debris from comets. C)... Some are clots of gas ejected from volcanoes on the outer planets. D)... Most are ejected from the Sun. E)... Both A and B.

5. What is the difference between a meteor and a meteorite?

A)... A meteorite is a very tiny meteor. B)... A meteorite is the pit made on the Earth or a planet when a meteor hits. C)... A meteor is the flash of light in the sky. A meteorite is the solid body ending up on the ground.  D)... A meteorite is the flash of light in the sky. A meteor is the solid body ending up on the ground. E)... A meteorite comes from a comet. A meteor comes from an asteroid.

6. Why can a rather small meteorite make such a big crater when it hits?

A)... It is so hot from its passage through the air that it melts the surroundings. B)... It contains acidic material that corrodes the surrounding surface where it hits. C)... The iron in it acts like a magnet and pushes the surrounding soil away. D)...It is traveling so fast that it has a very large kinetic energy even with small mass.  E)...It is made of anti-matter that annihilates the surface where it strikes.

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An asteroid, comet, or meteor impact can create a large crater because these objects strike the earth at very high speed...typicallly 30 km/sec (about 60,00 miles/hour!). The energy released is often enough to heat and vaporize both the impacting object and the surface where it hits. The expanding hot vapor then blasts a crater.Any moving object has energy because of its motion. That energy is technically called "kinetic energy." Mathematically, kinetic energy is mv²/2, where m is the object's mass and v its velocity.
Because the velocity enters as a square, a relatively small increase in velocity can lead to a large increase in energy.
In using the above formula for kinetic energy, the energy will be in units called joules if the mass is in kilograms and the velocity is in meters per second.
Because the energy released at impact is so high for even relatively small meteors, it will give you a better sense of their destructive power if you express the energy not in joules but in kilotons of TNT, the unit used to measure the explosive force of nuclear weapons.
1 kiloton of energy is 4x10¹² joules. Thus, it will make the significance of your answer clearer if you divide the answer you get in joules by 4x10¹². This will put your answer in kilotons.

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7. For example, about how much energy is liberated by a 5 metric ton (5x10³ kg ) asteroid hitting the Earth at 30 km/sec? (In working this problem, be sure to convert km/sec to meters/sec) . . multiply by 10³. Also, don't forget the 1/2 factor.

A)... 50 kilotons B)...0.5 kilotons  C)... 5 megatons D)...5000 joules. E)... 5 million megatons.

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About how big do you think a 5 ton meteorite would be? Turns out to be about the size of a typical kitchen stove.

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8. How was the first asteroid discovered?

A)... It collided with the Moon. B)...Galileo saw it whiz by Jupiter. C)...Piazzi found it by searching for objects at the distance suggested by Bode's law.  D)...Kepler traced back the path of meteors to the asteroid belt. E)...Newton inferred their existence by their gravitational influence on Jupiter.

9. What is a typical asteroid made of?

A)...Water frozen into ice. B)...Solid Carbon Dioxide and other gases. C)... Rock and iron.  D)... Liquid water. E)...Solid hydrogen.

10. About how big is the largest asteroid known in the Solar System?

A)... About the size of the Earth. B)... About one quarter the size of the Moon. C)...About 50 miles. D)... About 50 yards. E)...About 50 feet.

11. What is the asteroid belt?

A)...The place in the Solar System where most of the asteroids are found. B)...A line of craters on the Moon caused by an asteroidal impact about 50 million years ago. C)... A line of craters on the Earth caused by an asteroidal impact about 50 million years ago. D)...A term used to describe the impact of a very large asteroid with a planet. E)...None of the above.

12. What is the Kuiper Belt?

A)... A prize given to the person who discovers the most asteroids in a given year. B)...A region beyond Neptune in which a large number of small, icy objects orbit.  C)...A ring around Jupiter in which comets are captured. D)... A halo of light seen around some bright comets. E)...Streaks seen in the tails of some comets.

13. What is the Oort Cloud?

A)...Gas around a comet's head. B)...The glowing light around a meteor as it burns up. C)... A region in the outer Solar System from which comets come.  D)...A zone between the Sun and Mercury where comets burn up and release their gases. E)...The gas boiled off a comet that forms its tail.

14. In what direction does a comet's tail point?

A)... Toward the Sun, pulled by its gravity. B)...Away from the Sun. C)...Trailing the comet in its orbit. D)...Perpendicular to the comet's orbit. E)...Along the comets orbit in the direction the comet is moving.

15. What are comets made of??

A)...Mostly iron, rock, and hydrogen. B)...Mostly ice and frozen gases. C)...Mostly hydrogen and helium. D)... Mostly oxygen and uraium E)...None of the above.

16. What do asteroids have to do with dinosaurs?

A)...Dinosuars were brought to Earth on an asteroid. B)... An asteroid impact may have radically altered Earth's climate briefly and killed them.  C)...The asteroid belt formed at the time dinosaurs originated. D)...The asteroid belt formed at the time dinosaurs died out. E)...An asteroid impact killed off most of the mammals and allowed dinosaurs to proliferate.

17. How did comets and asteroids form?

A)...They are debris left over from the birth of the Solar System. B)... They are clots of matter ejected from volcanoes on the planets during their youth. C)...They are objects from interstellar space that drift through the Solar System. D)...They are debris ejected from the Sun in violent solar flares. E)...There are no theories to account for their origin.

18. How do astronomers know what comets consist of?

A)...A robot spacecraft has landed on one. B)... An astronaut has landed on one. C)...Light from them can be analyzed spectroscopically.  D)...X-ray telescopes have taken pictures of their insides. E)...The astronauts captured a comet during a recent space shuttle flight.