From laboratory measurements, we know that a particular spectral line formed by hydrogen atom appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?

From the information given, we can conclude that the star is moving towards us. This is based on the principle of the Doppler Effect, which states that the frequency (or wavelength) of a wave for an observer is altered if the source of the wave and the observer are moving relative to each other.

In this case, the wavelength of the spectral line from the star is shorter (485.9 nm) than the wavelength measured in the laboratory (486.1 nm). This shift to a shorter wavelength is known as a blue shift in the field of astronomy, which indicates that the star is moving towards us.

Here are the steps to reach this conclusion:

1. Compare the wavelengths: The laboratory measurement of the hydrogen line is at a longer wavelength (486.1 nm) than the star's hydrogen line (485.9 nm).

2. Apply the Doppler Effect: A shift to a shorter wavelength (blue shift) indicates that the object is moving towards the observer.

3. Conclusion: The star is moving towards us.