Are these galaxies moving toward or away from us? (Circle your choice.) Toward Away

1. The galaxy NGC 3147 is moving faster than NGC 3368. How can you tell?
2. The wavelength shifts of these galaxies are positive, making them redshifts. The redshift of galaxy NGC 3147 is 0.00935, and the redshift of NGC 3368 is 0.00301. From the Doppler formula, we know that wavelength shifts are proportional to the velocities of objects. Approximately how many times faster is NGC 3147 than NGC 3368? (Take a ratio of the redshifts and state the results.)
3. How many times farther away is NGC 3147 than NGC 3368?
4. Is there an inconsistency between the relative distances obtained from the redshifts of NGC 3147 and NGC 3368 and the relative distances calculated by the standard ruler method? Comment on your comparison.
5. Think about the underlying assumptions and methods used for the standard ruler and the direct measurements of wavelengths of lines in spectra. Which method is likely to give more accurate results? Explain.

Transcribed Image Text:

1.0 (a) NGC 3147-Calcium K(393.4 nm)and H(396.8 nm) www wm 0.8- 0.6- By 0.4 0.2+ 0.0 390 II 395 400 405 Wavelength (nm) 410 415 0.8 0.6+ NGC 3368 Calcium K(393.4 nm)and H(396.8 nm) wym 0.4- 0.2+ (b) Figure 9.3 0.0 W 390 Cak CaH 400 405 Wavelength (nm) 395 410 415 1.0 (a) NGC 3147-Calcium K(393.4 nm)and H(396.8 nm) www wm 0.8- 0.6- By 0.4 0.2+ 0.0 390 II 395 400 405 Wavelength (nm) 410 415 0.8 0.6+ NGC 3368 Calcium K(393.4 nm)and H(396.8 nm) wym 0.4- 0.2+ (b) Figure 9.3 0.0 W 390 Cak CaH 400 405 Wavelength (nm) 395 410 415