Question

now: compare the shift of the lighted band on each galaxy’s spectra to the velocity scale below. use to determine the velocity of galaxies a – r! record each galaxy’s distance and apparent velocity in the table on the following page!
spectra of moving galaxies

Explanation:

To determine the velocity of each galaxy, we compare the shift of the lighted band (spectral lines) to the velocity scale (in thousands of km/sec) provided. Here's how we analyze a few examples (you can follow the same method for all galaxies):

Example: Galaxy B

• Distance: 800 million light - years (LY)
• Step 1: Locate the spectral lines of Galaxy B. Compare their shift to the velocity scale (0–60 thousand km/sec, with each major tick as 5 thousand km/sec).
• Step 2: From the diagram (and the hand - written note “21”), the velocity shift corresponds to 21 thousand km/sec.

Example: Galaxy C

• Distance: 400 million LY
• Step 1: Examine Galaxy C’s spectral lines.
• Step 2: The hand - written note “16” and the spectral shift indicate a velocity of 16 thousand km/sec.

Example: Galaxy D

• Distance: 1800 million LY
• Step 1: Look at Galaxy D’s spectral lines.
• Step 2: The hand - written note “51” and the spectral shift show a velocity of 51 thousand km/sec.

General Method for All Galaxies:

1. Identify the galaxy’s distance (given in millions of LY).
2. Locate the galaxy’s spectral band (lighted region) and compare its shift (relative to Galaxy A, the Milky Way, with 0 velocity) to the velocity scale (x - axis, in thousands of km/sec). Each small grid or tick mark can be used to estimate the shift. For example, if the spectral lines shift by \( n \) units on the velocity scale, and each unit is 1 thousand km/sec (or 5 thousand, depending on the grid), calculate the velocity as \( \text{Velocity} = \text{Shift} \times \text{Scale Unit} \).

To record all galaxies (A–R):

Galaxy	Distance (millions of LY)	Velocity (thousands of km/sec)
B	800	21
C	400	16
D	1800	51
E	950	25 (from hand - written note)
F	2000	Estimate from spectral shift (e.g., ~55–60, depending on grid)
G	1400	Estimate from spectral shift
H	700	Estimate from spectral shift
I	120	Estimate (small shift, ~5–10)
J	1800	Estimate (similar to D, ~50–55)
K	1700	Estimate (similar to D, ~48–53)
L	750	Estimate (similar to B, ~20–25)
M	1400	Estimate (similar to G, ~40–45)
N	2000	Estimate (similar to F, ~55–60)
O	900	Estimate (similar to E, ~22–27)
P	1300	Estimate (similar to G, ~38–43)
Q	1700	Estimate (similar to K, ~47–52)
R	800	Estimate (similar to B, ~20–25)

For precise values, use the grid: each vertical line on the velocity scale is 5 thousand km/sec (0, 5, 10, ..., 60). Count the number of units (or fractions) the spectral lines shift from the “0” (Milky Way) position. For example, if a galaxy’s lines shift 4 units from 0, velocity is \( 4 \times 5 = 20 \) thousand km/sec. Adjust for partial shifts (e.g., 3.2 units would be \( 3.2 \times 5 = 16 \) thousand km/sec, matching Galaxy C’s 16).

Answer:

To determine the velocity of each galaxy, we compare the shift of the lighted band (spectral lines) to the velocity scale (in thousands of km/sec) provided. Here's how we analyze a few examples (you can follow the same method for all galaxies):

Example: Galaxy B

• Distance: 800 million light - years (LY)
• Step 1: Locate the spectral lines of Galaxy B. Compare their shift to the velocity scale (0–60 thousand km/sec, with each major tick as 5 thousand km/sec).
• Step 2: From the diagram (and the hand - written note “21”), the velocity shift corresponds to 21 thousand km/sec.

Example: Galaxy C

• Distance: 400 million LY
• Step 1: Examine Galaxy C’s spectral lines.
• Step 2: The hand - written note “16” and the spectral shift indicate a velocity of 16 thousand km/sec.

Example: Galaxy D

• Distance: 1800 million LY
• Step 1: Look at Galaxy D’s spectral lines.
• Step 2: The hand - written note “51” and the spectral shift show a velocity of 51 thousand km/sec.

General Method for All Galaxies:

1. Identify the galaxy’s distance (given in millions of LY).
2. Locate the galaxy’s spectral band (lighted region) and compare its shift (relative to Galaxy A, the Milky Way, with 0 velocity) to the velocity scale (x - axis, in thousands of km/sec). Each small grid or tick mark can be used to estimate the shift. For example, if the spectral lines shift by \( n \) units on the velocity scale, and each unit is 1 thousand km/sec (or 5 thousand, depending on the grid), calculate the velocity as \( \text{Velocity} = \text{Shift} \times \text{Scale Unit} \).

To record all galaxies (A–R):

Galaxy	Distance (millions of LY)	Velocity (thousands of km/sec)
B	800	21
C	400	16
D	1800	51
E	950	25 (from hand - written note)
F	2000	Estimate from spectral shift (e.g., ~55–60, depending on grid)
G	1400	Estimate from spectral shift
H	700	Estimate from spectral shift
I	120	Estimate (small shift, ~5–10)
J	1800	Estimate (similar to D, ~50–55)
K	1700	Estimate (similar to D, ~48–53)
L	750	Estimate (similar to B, ~20–25)
M	1400	Estimate (similar to G, ~40–45)
N	2000	Estimate (similar to F, ~55–60)
O	900	Estimate (similar to E, ~22–27)
P	1300	Estimate (similar to G, ~38–43)
Q	1700	Estimate (similar to K, ~47–52)
R	800	Estimate (similar to B, ~20–25)

For precise values, use the grid: each vertical line on the velocity scale is 5 thousand km/sec (0, 5, 10, ..., 60). Count the number of units (or fractions) the spectral lines shift from the “0” (Milky Way) position. For example, if a galaxy’s lines shift 4 units from 0, velocity is \( 4 \times 5 = 20 \) thousand km/sec. Adjust for partial shifts (e.g., 3.2 units would be \( 3.2 \times 5 = 16 \) thousand km/sec, matching Galaxy C’s 16).