The Universe

1. How many stars are there in the universe?

The universe is believed to have around  50 000 billion billion stars.

2.  How many stars are there in the Milky Way galaxy?

3. What is a galaxy?

A galaxy is a group of stars held together by the pull of gravity.

4. How many galaxies are there in the universe?

About 130 billion galaxies of different shapes and sizes.

5. What shape is the Milky Way?

Spiral shaped.

6. Which is the closest star to our solar system? How far is it? Why can’t we see it with the naked eye?

Proxima Centauri which is  40 000 billion kilometres away. It doesn’t emit enough light to be seen with the naked eye.

7. Which is the brightest star in the night sky? How far away is it?

Sirius which is twice as far away as Proxima Centauri.

8. How far is the sun from the Earth?

150 million kilometers.

9. What is a light-year? What is it used for?

One light-year is the distance that light travels in one year.

The distances between objects in the universe are so large that it is difficult to express them in kilometres. So a much larger unit called the light-year is used.

10. What is the speed of light?

300 000 kilometres per second.

11. What distance does light travel in a year or how much is one light-year?

9 500 billion kilometres.

12. How can we calculate distance in ligh-years?

Distance in light-years = distance in kilometres / one light-year

13. Express one million and one billion with zeroes.

1 million = 1 000 000

1 billion  = 1 000 000 000

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