Problem 1:Neptune.
Given that Neptune will be at opposition on 21 September 2024, calculate in which year Neptune was last at opposition near the time of the nort hern-hemisphere spring equinox. Assume that the orbits of Earth and Neptune are circular.
$(5points)$
Problem 2:Magnetic field.
An emission line of wavelength $ \lambda =600nm $ was observed in the spectrum of a white dwarf.Assuming that it originates from the interaction of a free non-relativistic electron with a magnetic field
$(a).$ calculate the magnetic flux density of the field;
$(b).$ estimate the wavelength of another spectral line, the discovery of which could confirm that the lines originate from particles of a plasma interacting with the magnetic field.
$(5points)$