1. What do you see in the photographs of the sky?

5. Summary of Night Sky Observations
(Star Notes)

6. 1. There are a LOT of stars in the sky.
Over 3 billion stars (3,000,000,000) can be seen through ground- based telescopes.

7. 2. Stars have different sizes; some are small, some large.
The smallest stars are smaller than Earth.
The largest stars are 1,000 times the diameter of the Sun.

8. 3. Stars are different colors.
The color of a star indicates its surface temperature.

9. The color of a star indicates its surface temperature:
Blue: highest temperatures
(> 30,000°C)
White (≈10,000°C)

10. Yellow (≈5,000°C) the Sun
Orange (≈4,000°C)
Red: lowest temperatures (<3500°C)

11. 4. Some stars are brighter than others.
A star’s apparent brightness depends on
the star’s size
surface temperature
its distance from us

12. 4. Some stars are brighter than others.
A really bright star that is far from us will look dim.

13. There are colored “clouds” (red, blue, pink, black, etc) visible in some areas.
These are nebulas, extremely large clouds of gas and dust in space.
Light from stars is what causes the nebula to glow.

14. 5. There are colored “clouds” (red, blue, pink, black, etc) visible in some areas.
Blue nebulas often indicate new stars are forming.
Red nebulas are often the remains of exploded stars.

15. 6. There are areas with more or less stars.
Stars often stay in “clumps” or “clusters” because gravity keeps them near each other.

16. Clusters of Stars/Galaxies

17. 6. There are areas with more or less stars.
Some areas which actually have a lot of stars are hidden from our view by dark clouds of gas and dust.

18. 6. There are areas with more or less stars.
Some stars that appear close to each other may actually be separated by huge distances (one closer to us than another).

19. The most important property of a star is its mass.
STARS
The most important property of a star is its mass.

20. A star’s mass determines:
How the star will change over time.
Size, temperature/color, brightness, star type
The star’s gravitational attraction.

21.
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