Both planets will be visible to the naked eye for the next two weeks as bright, starlike objects that will dominate the low western sky shortly after sunset.

"From a place with a low horizon, one should be able to get a nice view of these two planets hanging in the darkening sky like gems," said Geza Gyuk, staff astronomer at the Adler Planetarium in Chicago.

As the cosmic duo climb higher, the'll reach conjunction—their closest approach to each other—on Saturday and Sunday.

Those nights the two planets will seem to be separated by only three degrees, or the equivalent of six full-moon disks.

Of the five planets visible to the naked eye, Mercury is usually the most challenging to