Astronomy 201 HM - CH 15 #1-5

3) Visual Activity: A Graph of Hubble's Law Part E- The age of the universe is related to the slope of the graph of Hubble's law, and current data put the age of the universe at about 14 billion years. Suppose that future observations showed that the slope of Hubble's law on the graph is actually steeper than that shown. In that case, the age of the universe would be _________ than 14 billion years because the universe is expanding ______ than current data suggest. (Each choice gives words to fill in the two blanks, separated by a slash.)

younger / more rapidly

1) Hubble's galaxy classification - Astronomers observe galaxies and categorize them according to four different kinds of shapes: elliptical, spiral, barred-spiral, and irregular. In addition to shape, each of the four different galaxy types can be described by other common characteristics. Match the following characteristics with their corresponding galaxy type.

Eliptical galaxy (E) - Round, no disk, very little gas and dust, only old stars Spiral galaxy (S)- Central bulge, flattened disk, spiral arms, gas, dust, young stars. Barred-spiral galaxy (SB) - Elongated central structure, flattened disk, spiral arms, gas and dust, young stars. Irregular galaxy (Irr) - Asymmetric, often with gas, dust, and young stars.

3) Visual Activity: A Graph of Hubble's Law Part C- Suppose that galaxy B is twice as far from Earth as galaxy A. Hubble's law predicts that galaxy B will be moving away from Earth with approximately _____.

twice the velocity of galaxy A

2) Understanding Hubble's Law Part B- The following figures give the approximate speeds at which five galaxies are moving away from Earth due to the expansion of the universe. Rank the galaxies based on their distance from Earth, from farthest to closest.

130,00 km/s 45,00 km/s 18,730 km/s 5,265 km/s 1,577 km/s

3) Visual Activity: A Graph of Hubble's Law Part B- By looking at the graph, what can we say about the galaxies that have the lowest speeds?

They are moving away from Earth and are closer to Earth than galaxies with high speeds.

3) Visual Activity: A Graph of Hubble's Law Part A- The graph shows that galaxies with high speeds as measured from Earth are ______.

moving away from Earth and are farther from Earth than galaxies with lower speeds

1) Edwin Hubble photographed galaxies and classified them according to their apparent shapes. Label the diagram of Hubble's classification system according to the broad categories of galactic shapes.

(a)Elliptical (b)Spiral (c)Irregular (d)Barred-spiral

2) Understanding Hubble's Law Part C- The following figures give the approximate speeds at which five galaxies are moving away from Earth due to the expansion of the universe. Rank the galaxies based on the amount of redshift that would be observed in each galaxy's spectrum, from largest to smallest.

130,00 km/s 45,000 km/s 18, 730 km/s 5,264 km/s 1, 577 km/s Redshift tells us that an object is moving away from us, and the larger the redshift, the higher the speed.

2) Understanding Hubble's Law Part A- The following figures give the approximate distances of five galaxies from Earth. Rank the galaxies based on the speed with which each should be moving away from Earth due to the expansion of the universe, from fastest to slowest.

5 billion light-years, 2 billion light-years, 800 million light-years, 230 million light-years, 70 million light-years Hubble's law tells us that the more distant a galaxy is from Earth, the faster it is moving away from us.

3) Visual Activity: A Graph of Hubble's Law Part D-Imagine that when we looked out into the universe we found that the light from all galaxies was blueshifted (rather than redshifted) and that the light from the most distant galaxies was blueshifted by the greatest amount. Which statement best describes what we would conclude about the motions of galaxies in this case?

All are moving toward Earth, with distant galaxies moving faster than nearby galaxies.

2) Understanding Hubble's Law Part E- The following four graphs are the same as those from Part D, with each showing a possible relationship for Hubble's law. Rank the graphs based on the prediction they each would make for the current age of the universe, from oldest to youngest.

Distance approaching 1200, 10,000 Distance approaching 1200, 20,000 Distance approaching 800 Distance approaching 400

2) Understanding Hubble's Law Part D- Hubble's law is a relationship between galaxy speeds and galaxy distances. This relationship can be shown as a line on a graph of speed versus distance. Each of the following four graphs shows a possible relationship expressing Hubble's law. Rank the graphs based on their predictions of the speed, from fastest to slowest, for a galaxy located 400 million light-years away from Earth.

Distance approaching 400 Distance approaching 800 Distance approaching 1200, 20,000 Distance approaching 1200, 10, 00 If you look at the speed corresponding to a distance of 400 million light-years on each graph, you will see that the speed declines in the order shown. Note also that this ranking puts the graphs in order of declining steepness. In other words, a steeper slope for Hubble's law would predict faster speeds for galaxies at particular distances.

1) Since the time of Hubble, astronomers have learned that the blue color observed in some galaxies is the result of recent star formation. The blue regions can be seen in the following figure, where the color differences are schematically depicted. This interpretation has been confirmed by multiwavelength observations that have revealed the presence of star-forming gas clouds in galaxies hosting newly formed O-and B-type stars. Sort the galaxy types according to their level of star-forming activity.

Little star-forming activity : Elliptical galaxies Significant star-forming activity: Irregular galaxies, spiral galaxies, barred-spiral galaxies

Describe the four rungs in the distance-measurment ladder used to determine the distance to a galaxy lying 5 Mpc away.

There are four rungs in the distance-measurement ladder to determine the distance to a galaxy lying 5 Mpc away. These four rungs are

1) The irregular classification is in some ways a method of dealing with galaxies that are clearly not elliptical or spiral in shape. Select the properties associated with irregular galaxies. Check all that apply.[*]

[*]Some show evidence for prior collision or close encounter with another galaxy. [*]They exhibit vigorous star-forming activity. [ ]They have tightly wound spiral arms. [ ]They all have centrally concentrated starlight. [ ]They are rare. [*]They are typically smaller than spiral galaxies.