Astronomy Exam #2

Suppose Earthʹs atmosphere had no greenhouse gases. This would cause Earthʹs average surface temperature to be

well below the freezing point of water.

What is a magnetosphere?

a region of space around a planet in which the planet’s magnetic field can affect charged particles

What is the solar wind?

A stream of charged particles flowing outward from the surface of the Sun

What do we mean by the frost line when we discuss the formation of planets in the solar nebula?

It is a particular distance from the Sun, beyond which the temperature was low enough for ices to condense.

Which of the following best describes convection?

It is the process in which warm material expands and rises while cool material contracts and falls.

By what process does the Sun generate energy?

nuclear fusion

The Sun’s visible surface (that is, the surface we can see with our eyes) is called the _____

photosphere

Based on our current theory of Earthʹs formation, the water we drink likely comes from

water bearing planetesimals that impacted Earth.

The fundamental nuclear reaction occurring in the core of the Sun is _______

nuclear fusion of hydrogen into helium

Why does the burning of fossil fuels increase the greenhouse effect on Earth?

Burning releases carbon dioxide into the atmosphere.

According to modern science, approximately how old is the Sun?

4.5 billion years

What kind of material in the solar nebula could condense at temperatures as high as 1,500 K, such as existed in the inner region of the nebula?

metals

What is the major difference between asteroids and comets?

Asteroids are rocky and comets are icy

The Sunʹs average surface (photosphere) temperature is about ________

5,800 K

According to our theory of solar system formation, what are asteroids and comets?

leftover planetesimals that never accreted into planets

Why do sunspots appear dark?

They are regions that are significantly cooler than the rest of the photosphere.

What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?

Gravitational force and outward pressure

Why do sunspots appear dark?

They are regions that are significantly cooler than the rest of the photosphere.

Why did the solar nebula heat up as it collapsed?

As the cloud shrank, its gravitational potential energy was converted to thermal energy.

According to the nebular theory, what are asteroids and comets?

Leftover planetesimals that never accreted into planets

What would happen in the Sun if the temperature of the core decreased?

The fusion rate decreases, then the core shrinks and heats.

Why did the solar nebula heat up as it collapsed?

As it shrank in size, gravitational potential energy was converted to thermal energy

The Sunʹs surface is called the ________

photosphere

Suppose you try to bring two protons close together. Because of the electromagnetic force, the two protons will

repel one another

What do we mean by accretion in the context of planet formation?

the growth of planetesimals from smaller solid particles that collided and stuck together

Satellites in low-Earth orbits are more likely to crash to Earth when the sunspot cycle is near solar maximum because ________

Earthʹs upper atmosphere tends to expand during solar maximum, exerting more drag on satellites in low orbits

Which planet has the highest average surface temperature, and why?

Venus, because of its dense carbon dioxide atmosphere

According to our theory of solar system formation, which law best explains why the solar nebula spun faster as it shrank in size?

the law of conservation of angular momentum

Energy balance in the Sun refers to a balance between _______

the rate at which fusion generates energy in the Sunʹs core and the rate at which the Sunʹs surface radiates energy into space

What happens to energy in the Sunʹs convection zone?

Energy is transported outward by the rising of hot plasma

From the center outward, which of the following lists the ʺlayersʺ of the Sun in the correct order?

Core, radiation zone, convection zone, photosphere, chromosphere, corona

How can we best observe the Sunʹs chromosphere and corona?

The chromosphere is best observed with ultraviolet telescopes and the corona is best observed with X-ray telescopes.

When we say that the Sun is a ball of plasma, we mean that ________

the Sun consists of gas in which many or most of the atoms are ionized (missing electrons)

In essence, the solar nebular theory states that ________

our solar system formed from the collapse of an interstellar cloud of gas and dust

How does the Sunʹs mass compare to Earthʹs mass?

The Sunʹs mass is about 300,000 times the mass of the Earth

According to our theory of solar system formation, which law best explains why the central regions of the solar nebula got hotter as the nebula shrank in size?

The law of conservation of energy

What do we mean by the frost line when we discuss the formation of planets in the solar nebula?

It is a circle at a particular distance from the Sun, beyond which the temperature was low enough for ices to condense

helium, gamma rays, and neutrinos.

Why is the sky blue (on Earth)?

because molecules scatter blue light more effectively than red ligh

What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?

gravitational force and outward gas pressure

Why does the Sun emit neutrinos?

Fusion in the Sunʹs core creates neutrinos when protons turn into neutrons.

What is the primary product created by the fusion of hydrogen in the core of the Sun?

Helium

Considering only the tilt of their axis, which planet listed below would have the most extreme seasons?

Uranus

Why do sunspots appear dark in pictures of the Sun?

They actually are fairly bright, but appear dark against the even brighter background of the surrounding photosphere.

The source of energy that keeps the Sun shining today is ________

nuclear fusion

The Sunʹs average surface (photosphere) temperature is about ________

5,800 K

Approximately, what is the Sun made of (by mass)?

70% hydrogen, 28% helium, 2% other elements

How do scientists determine the age of the solar system?

radiometric dating of meteorites

Suppose you put two protons near each other. Because of the electromagnetic force, what will the two protons do?

Repel each other

What is the solar wind?

a stream of charged particles flowing outward from the surface of the Sun