An astronomer discovers a new galaxy using a telescope. The astronomer wants to investigate how the galaxy is moving relative to the Milky Way galaxy.
make a hypothesis about the movement of the galaxy and explain at least one way to test the hypothesis.
Hypothesis: The new galaxy is moving away from the Milky Way galaxy, indicating an expansion of the universe.
One way to test this hypothesis is by measuring the redshift of prominent spectral lines in the galaxy's spectrum. The redshift results from the stretching of light waves, causing them to appear longer and redder. This phenomenon is associated with the Doppler Effect, where the motion of an object causes a shift in the wavelength of light it emits. A redshift in the galaxy's spectrum would indicate that it is moving away from the Milky Way.
To test the hypothesis, the astronomer would first obtain a spectrum of the galaxy's light using a spectrograph attached to the telescope. They would then carefully analyze the spectrum by identifying several prominent spectral lines, which serve as reference points for their original wavelengths. By comparing the observed wavelengths of these lines to their known or laboratory wavelengths, the astronomer can calculate the redshift.
If the redshift value calculated is positive, it would confirm that the galaxy is indeed moving away from the Milky Way. Additionally, the magnitude of the redshift can provide information about the speed of the galaxy's movement. A larger redshift indicates a faster relative motion away from us and vice versa.
By conducting multiple observations of the galaxy over a period of time, the astronomer can also determine if the redshift remains consistent, suggesting a constant motion. Alternatively, if the redshift value changes significantly, it may indicate that the galaxy's movement is influenced by external forces such as gravitational interactions with other galaxies.