Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude

Answer: we can conclude that the wavelength is decreasing. This means that the star is moving towards the observer on earth.

Explanation:

Since light has a constant speed of 3 x 10^8m/s, and this speed is a product of its wavelength and its frequency c = f¥

Where f is the frequency and ¥ is the wavelnght.

For a decreasing wavelength, it is seen that the frequency is increasing.

According to the doppler's effect, a moving body that is a source of a wave of frequency f, moving relatively towards an observer, the frequency will increase as they move closer to a frequency f' which is greater than f. This is known as the doppler shift of light wave.

It means that the star is moving towards us.

Explanation:

The star is moving toward us; shift to a shorter wavelength. A shorter wavelength means a shift to the blue end of the spectrum (a blueshift) so that the object is moving toward us.