Tonight skygazers may have a chance to observe a "planetary parade," where seven planets -- Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune -- appear together in the evening sky. Take note that to see them all, you will need an almost completely unobstructed view, as several will sit very close to the horizon line. Others will require special equipment. Therefore, it is a bit exaggerated to call this a Seven Planet Parade because of those limitations.
Just after sunset, look toward the western horizon to spot Mercury and Saturn, which will be low and require an unobstructed view. Venus, the brightest planet, will be easily visible, while Mars will stand out with its reddish hue higher in the sky. Jupiter will also be prominent without the need for special equipment. Uranus and Neptune, however, will require binoculars or a telescope to be seen clearly.
This alignment is a result of the planets' orbits bringing them to the same region of the sky from our viewpoint on Earth. Planets always line up in the sky because they orbit the Sun on the same flat path, like cars moving on a giant racetrack. Using the same analogy, since we're inside of this racetrack, we see the planets following a curved line across the sky, called the ecliptic.
While planets aligning isn't rare, what makes these events exciting is that we get to see several planets at once without needing a telescope. Four- and five-planet lineups happen every few years, with Mars, Jupiter, and Saturn often visible. Adding Venus and Mercury makes these events special. These "planet parades" last weeks, not just a day.