Mercury on the Horizon
Credit: Juan Carlos Casado
Have you ever seen the planet Mercury?
Because
Mercury orbits so close to the Sun,
it is never seen far from the Sun,
and so is only visible near
sunrise or
sunset.
If trailing the Sun,
Mercury will be visible
for several minutes before it follows the
Sun behind the
Earth.
If leading the Sun,
Mercury will be
visible for only several minutes before the
Sun rises and hides it with increasing glare.
An
informed skygazer can usually pick Mercury out of a dark
horizon glow
with little more than determination.
Above, a lot of determination has been combined
with a little
digital trickery to
show Mercury's successive positions
during the middle of last month.
Each picture was taken from the same location in Spain
when the Sun was 10 degrees below the
horizon and superposed
on the single most
photogenic sunset.