Unit 6 Space Science A "Exemplary"

Question 1

Describe the evidence for multiple galaxies in the universe.

Answer 1

In the early 1920s new telescopes allowed scientists to identify individual stars too distant to be part of the Milky Way galaxy. In 1999 the Hubble Space Telescope provided direct observations of thousands of galaxies. Therefore, scientists now estimate there are at least 100 billion galaxies in the universe.

Question 2

Explain why the terrestrial planets are dense and rocky but the gas giants are larger and have low densities according to nebular theory.

Answer 2

• When the solar system formed, temperatures near the sun were so high that ice-forming compounds vaporized and only rock-forming compounds could condense to form the inner rocky planets.
• The outer solar system was colder allowing the ice-forming compounds to condense and form larger planets with greater gravity to capture abundant gases from space.

Question 3

Explain how scientists use an H-R diagram to estimate a star’s size.

Answer 3

Stars on a H-R diagram are classified by absolute brightness (absolute magnitude) and surface temperature (or color). If two stars are the same temperature/color, the brighter one must be larger. Similarly, hotter stars are brighter than cooler stars of the same size.