In astronomical terms, a planetary parade, or alignment, refers to the phenomenon where several planets in our solar system appear to be in a line when observed from Earth. The event you’re referring to, involving seven planets, is not exceedingly common, making it a noteworthy event for skywatchers. Such alignments of multiple planets don’t happen every year, and when they do occur, they are a result of the planets’ differing orbits around the Sun.
Planets typically align on the same side of the Sun over a span of years due to their varying orbital speeds and distances from the Sun. The frequency of a seven-planet alignment—involving visible planets like Mercury, Venus, Mars, Jupiter, Saturn, and possibly Uranus and Neptune, which require a telescope—can vary. Depending on the specific configuration, it might occur a few times in a century. These alignments do not imply a perfect straight line or equal spacing, but rather that the planets fall within a small section of the sky as viewed from Earth.
What makes this celestial event particularly interesting next month is its visibility and the opportunity for both amateur and professional astronomers to observe much of the solar system in a single night. While not a rare event on the scale of planets’ billions of years of history, such alignments capture the attention of those interested in the night sky because of their rarity in within the span of a human lifetime.