Mercury's orbit is
so close to the Sun that we can only see it from Earth either just before
sunrise or just after sunset. Below is a diagram of the orbits of the
inner planets, as they appear today. In this view, the planets
are all traveling counterclockwise about the Sun, and the Earth is rotating
counterclockwise about its axis as well.
Do you think you should look for Mercury around sunrise or sunset? To see
views of the sky at sunrise and sunset today, select the city nearest you
in the menu box below, and click the "submit" button. In each
diagram, the horizon is at the bottom and the directions are
labelled just below. The positions of the inner planets are shown,
and the yellow line is the path of the Sun just after sunrise or just before
sunset. The time and date are stamped at the upper left corner of each picture.
If you want to see Mercury well with the naked eye, it's best to choose a time
of year when the planet is above the horizon while the sky is fully dark - at least 40
minutes or so before sunrise, or after sunset. This means that Mercury is most visible at
those times of year when it is at least 10 degrees above the horizon at sunrise
or sunset. The diagrams can show you whether this is true today - notice that a scale
of degrees of elevation is along the left side of each picture. Look in the direction
where the Sun will rise in the morning, or where it has set in the evening, and you
may be rewarded with a view of the innermost planet.
This page uses the Java applet "Sky View Cafe" with permission of its developer,
Kerry Shetline. To explore the full power of the applet, we encourage you to visit the
Sky View Cafe website