Astronomy Test #2

By way process does the Sun generate energy?

nuclear fusion

At the center of the Sun, nuclear fusion converts hydrogen into

helium, gamma rays, and neutrinos

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

repel one another

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

4.5 billion years

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

gravitational force and outward gas pressure

Why do sunspots appear dark?

they are regions that are significantly cooler than the rest of the photosphere

"Energy balance" in the Sun refers to the balance between

the rate at which fusion generates energy in the Sun's core and the rate at which the Sun's surface radiates energy into space

The Sun's surface is called the

photosphere

The Sun's average surface (photosphere) temperature is about

5,800 K

What is the solar wind?

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

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

nuclear fusion of hydrogen into helium

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

Venus (because of its dense carbon dioxide atmosphere)

Why did the solar nebula heat up as it collapsed?

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

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

Based on our current theory of Earth's formation, the water we drink likely comes from

water bearing planetesimals that impacted Earth

In essence, the solar nebular theory states that

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

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

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

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

leftover planetesimals that never accreted into planets

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

Uranus

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

How do scientists determine the age of the solar system?

radiometric dating of meteorites

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)

What happens to energy in the Sun's "convection zone"?

energy is transported outward by the rising of hot plasma

How can we best observe the Sun's chromosphere an corona?

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

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

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

Which of the following best describes "convection"

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

Suppose Earth's atmosphere had no greenhouse gases. This would cause Earth's 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

Why is the sky blue (on Earth)?

because molecules scatter blue light more effectively than red light

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

burning releases carbon dioxide into the atmosphere

How does the Sun's mass compare to Earth's mass

The Sun's mass is about 300,000 times the mass of the Earth

Why does the Sun emit neutrinos?

fusion in the Sun's core creates neutrinos when protons turn into neutrons

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

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

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