The three have been arranged in a triangle for weeks but have now moved to form a straight line, ending at the red giant star Antares in the constellation Scorpius.

Backyard telescopes will offer an up-close look at both of the planets in the line. Mars will appear as a small orange-hued disk with a white polar cap and dark features dotting its surface, while Saturn’s rings, cloud belts, and largest moon Titan will all be clear to see. By Friday evening, Mars will appear to slide off to the south on a lonely path toward Sagittarius.

Known as Messier 35, the cluster consists of several hundred stars and measures about 24 light-years across. It’s visible to the naked eye, but binoculars