Milky Way Scales - Study Notes

Milky Way Scales Tutorial

Objective

  • This tutorial aims to provide a better understanding of the size of the Milky Way Galaxy by exploring the distances and sizes of various objects both within and outside the Milky Way.

Milky Way Representation

  • A picture representing a spiral galaxy similar to the Milky Way is provided.

  • Due to our position within the Milky Way, capturing an image of the entire galaxy is impossible. /

  • For illustration purposes in the picture:

    • 1 centimeter (cm) in the diagram corresponds to 10,000 light-years (ly).

    • 1 millimeter (mm) corresponds to 1,000 light-years (ly).

Distance Measurements

  1. Sun's Distance to the Center of the Milky Way:

    • The picture indicates the approximate distance from the Sun to the center of the Milky Way. Given that 1 cm = 10,000 ly, an estimation can be derived.

  2. Estimating Distances for Locations A-E:

    • Students are tasked with estimating distances from the center of the Milky Way to five specified locations (A-E).

    • Results are to be recorded in a table format specifying distances in light-years (ly).

    • Example of Distance Measurements:

      • Location A: X ly

      • Location B: Y ly

      • (Continue for all locations)

Bright Stars Distance Table

  1. Stars in the Night Sky:

    • A table lists five notable stars along with their distances from the Sun:
      | Star | Distance from Sun (ly) | Letter (A-E) |
      |---------|---------------------|----------------|
      | Sirius | 8 | A |
      | Vega | 26 | B |
      | Spica | 260 | C |
      | Rigel | 810 | D |
      | Deneb | 1,400 | E |

Student Discussion Questions

  1. Student Insights on Star Placement:

    • Discussion between two students reveals differing opinions on the placement of stars based on their distances.

    • Student 1's placements:

      • Sirius at A, Vega at B, Spica at C, Rigel at D, and Deneb at E.

    • Student 2 argues:

      • Deneb should correspond to only a little more than 1 mm from the Sun in the given picture.

      • Both students can have valid points regarding the distances.

  2. Is Deneb Distant in Context of the Milky Way?:

    • Inquiry posed to evaluate whether Deneb's distance (1,400 ly) compared to the size of the Milky Way Galaxy qualifies it as distant.

  3. Inside or Outside the Milky Way?:

    • Evaluate whether the stars listed in question 3 are located inside or outside the Milky Way Galaxy.

Messier Objects and Their Locations

  1. Messier Objects Distance Assessment:

    • The table below includes three Messier objects, with their respective distances from the Sun to assess their locations against the Milky Way diagram.
      | Messier Object | Distance from Sun (ly) | Letter (A-E) |
      |---------------------------------|---------------------|----------------|
      | M45 Open Cluster (Pleiades) | 380 | Example Letter |
      | M1 (Crab Nebula) | 6,300 | Example Letter |
      | M71 Globular Cluster | 12,700 | Example Letter |

Messier Objects and the Milky Way

  1. Are Messier Objects Part of the Milky Way?:

    • Explanation required to determine if listed Messier objects fall within the Milky Way Galaxy.

  2. Drawing the Crab Nebula:

    • The Crab Nebula has a width of about 11 light-years.

    • Determination on whether to use a small blob or tiny dot to accurately represent it on the diagram provided in question 7.

    • Note: The dots marking locations on the diagram are approximately 1 mm across.

  3. Representation of the Sun:

    • Discussion on whether the dot used to represent the Sun is too small, too large, or just right when compared to the actual size of the Sun.

Local Group and Other Galaxies


  2. Local Group Galaxy Distances:

    • The Milky Way Galaxy is identified as one of the largest galaxies in the Local Group.


    • Distances to centers of other Local Group galaxies are provided:

      Galaxy

      Distance from Sun (ly)


      Sagittarius Dwarf Elliptical Galaxy (SagDEG)

      80,000


      Large Magellanic Cloud (LMC)

      160,000


      Andromeda Galaxy (M31)

      2,500,000

      • Inside or Outside the Milky Way:

      • Evaluation of whether the galaxies mentioned in question 11 are located inside or outside the Milky Way Galaxy.

      • Size Representation of SagDEG:

      • SagDEG is approximately 11,000 ly across.

      • Determination of whether it is better represented on the diagram as a small blob or tiny dot, including reasoning and sketch representation.

      • Distance of Andromeda Galaxy:

      • The distance of the Andromeda Galaxy from the Sun is noted as 2,500,000 ly, which corresponds to 250 cm (2.5 meters or 8 feet) on the diagram.

      • Inquiry about how far the Virgo Cluster is which is about 60,000,000 ly away, and how this distance translates into centimeters on the picture diagram.

      Conclusion

      • Final considerations regarding the vastness of space, the size of galaxies, and the implications of understanding astronomical distances.