W7

The most common element in the Sun is

Hydrogen

What is the best reason astronomers have come up with to explain why sunspots are cooler and look darker?

Sunspots are places where the strong magnetic fields in the Sun resist the upward motion of bubbling hot gases from underneath

Which statement about the Sun's rotation is TRUE?

The Sun rotates at different rates at different latitudes on the Sun

Astronomers have concluded that the Sun's activity varies in an 11-year cycle. Which of the following statements about this cycle is TRUE:

The number of sunspots gets larger and smaller over the course of 11 years

Which of the following statements about the Sun's photosphere is NOT TRUE?

The photosphere is significantly hotter than all the layers of the Sun beneath it (further inward)

Astronomers have found that the level of the Sun's activity varies over the centuries. How did they come to realize that this is so:

all of the above •measuring the amount of radioactive carbon in tree rings •historical records of the number of sunspots seen on the Sun •historical records of auroral activity

Solar wind particles can be captured by the Earth's magnetosphere. When these particles spiral down along the magnetic field into the atmosphere, they are responsible for:

aurorae (northern and southern lights)

The ten million tons of particles that escape the Sun each year in the form of the solar wind get out mainly through regions called

coronal holes

The Sun's chromosphere and corona were discovered

during total eclipses of the Sun

The granulation pattern that astronomers have observed on the surface of the Sun tells us that:

hot material must be rising from the Sun's hotter interior

As astronomers have learned more about the structure of the Sun, they have found that it

is made entirely of hot gas

When we use the light of atoms such as hydrogen and calcium to examine the Sun's outer layers, we can see bright "clouds" in the chromosphere right around the location of sunspots. These bright clouds are given the name:

plages

Sunspots are darker than the regions of the Sun around them because

they are cooler than the material around them (although still very hot compared to Earth temperatures)

How do astronomers know how strong the magnetic field of the Sun is?

they measure the Zeeman effect (the splitting of spectral lines)