#### Our Sun – Quiz

The Solar System was made from the leftovers of the formation of the Sun. How much do you know about the star that makes life on Earth possible? Try the quiz – then you can check your answers, and learn more about our Sun.

Quiz: Our Sun

1. The approximate age of the Sun is: (A) 75 million years; (B) 5 billion years; (C) 1 trillion years.

2. The mass of the Sun is what percentage of the mass of the whole Solar System? (A) 55%; (B) 78.5%; (C) 99.8%.

3. About how many miles across is the Sun? (A) 150,000 km (95,000 mi); (B) 550,000 km (340,000 mi); (C) 1,400,000 km (870,000 mi).

4. The mean distance from the Earth to the Sun is an astronomical unit (AU). An AU is equal to about: (A) 97 million km (60 million mi); (B) 150 million km (93 million mi); (C) 200 million km (124 million mi).

5. The Sun is a nuclear reactor – its main fuel is: (A) hydrogen; (B) oxygen; (C) helium

6. A sunspot looks dark because: (A) it's not as hot as the rest of the surface of the Sun; (B) it's deep under the surface of the Sun; (C) it's the shadow of a transiting planet.

7. We can't usually see this part of the Sun except during a solar eclipse: (A) the photosphere; (B) the corona; (C) a prominence.

8. A stream of particles continuously flows out from the Sun into the Solar System. It's called: (A) a solar flare; (B) a coronal mass ejection; (C) the solar wind.

9. A geomagnetic storm: (A) can cause severe weather on Earth; (B) can damage power stations; (C) has no effect except to cause colorful auroras.

10. When the Sun runs out of fuel, it will collapse into a: (A) white dwarf; (B) black hole; (C) red dwarf.

1. The approximate age of the Sun is: (B) 5 billion years.

2. The mass of the Sun is what percentage of the mass of the whole Solar System? (C) 99.8%.
All of the planets, dwarf planets, moons, asteroids, Kuiper Belt objects and comets taken together account for only 0.2% of the Solar System's mass.

3. About how many miles across is the Sun? (C) 1,400,000 km (870,000 mi).
The Sun is big. You could line up more than 100 Earths across a circle with the diameter of the Sun.

4. The distance from the Earth to the Sun is called an astronomical unit (AU). An AU is equal to about: (B) 150 million km (93 million mi).
Astronomers use the AU to describe distances in the Solar System. For example, Neptune's average distance from the Sun is about 30 AU. That's much easier to work with than 4.5 billion km or 2.8 billion miles.

5. The Sun is a nuclear reactor – its main fuel is: (A) hydrogen.
The Sun is a main sequence star, which means that it's still fusing hydrogen into helium. Later in its evolution, it will use helium as its nuclear fuel.

6. A sunspot looks dark because: (A) it's not as hot as the rest of the Sun.
The surface temperature of the Sun is 5500°C (9900°F). Sunspots are cooler than that, but at 3900°C (7100°F), they're still quite hot. When Mars or Venus transits the Sun, it passes between us and the Sun. We see a planet as a black circle against the Sun's brilliance. It's not possible for anything to cast a shadow on the Sun.

7. We can't usually see this part of the Sun except during a solar eclipse: (B) the corona.
The colored part of the Sun that we normally see is the photosphere where the sunspots are. A prominence is an enormous bright eruption of gas from the surface of the Sun. It's visible through a telescope. The corona is a very tenuous layer that's normally swamped by light from the photosphere. It is however visible when the main body of the Sun is blocked by the Moon. (You can see the solar corona in the header image for this article. Photo credit: NASA/S. Habbal, M. Druckmüller and P. Aniol)

8. A stream of particles continuously flows out from the Sun into the Solar System. It's called: (C) the solar wind.
Solar flares and coronal mass ejections (CMEs) are occasional releases of particles and energy, but the solar wind is continuous. It sends charged particles through the Solar System out to well beyond Pluto and the Kuiper Belt.

9. A geomagnetic storm: (B) can damage power stations.
A geomagnetic storm doesn't cause thunderstorms and is usually only noticeable by the aurorae that it causes. However a strong geomagnetic storm can damage satellites and power stations. In 1989 such a storm caused Canada's Hydro-Québec power utility's grid to crash, knocking out electricity to six million people in northeastern Canada for several hours.

10. When the Sun runs out of fuel, it will collapse into a: (A) white dwarf.
When the Sun runs out of hydrogen, it will expand into a red giant star and use helium as a fuel. When it uses up the helium, nuclear fusion will stop. It will collapse into a hot white dwarf that gradually cools. It won't ever be a black hole because that's only the fate of stars much more massive than the Sun.

How did you do?
Did you get the answers right? If not, would you do better next time from what you've learned?

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