For the last month and change, you might’ve seen the headlines about the planetary alignment, or a planetary parade, going on in our solar system. And that’s true. In January 2025, Venus, Mars, Jupiter, Saturn, Uranus and Neptune were all visible in the night sky. And in February, 2025, Mercury will join the fun, with all seven of our planetary neighbors visible from Earth.
So what does such a planetary alignment mean for science? Well, truthfully, not much. A planetary alignment occurs “when the planets ‘line up’ on the same side of the sun, generally speaking,” Gerard van Belle, Lowell Observatory’s director of science, tells Space.com. “When this happens, we can see multiple planets in the night sky.” And that’s about it! In other words, this planetary parade is simply an excellent reason to go stargazing — or planet-gazing, if you will.
But if you’re curious about all the hoopla surrounding planetary alignments, here’s what you need to know about this (usually) non-scientific phenomenon.
What is a planetary alignment?
The term “planetary alignment” isn’t a scientific one, but a catch-all colloquial phrase that can refer to multiple astronomical events. In the eyes of the general public, it typically means that we can see multiple planets at once. Interestingly, they’ll always appear along the same arc in the night sky. That path is called the ecliptic, and it exists because all planets in our solar system orbit around the sun on roughly the same plane.
Astronomers, on the other hand, look for more specific planetary alignments, such as oppositions and conjunctions. In a very basic distillation of their definitions, these terms refer to the positions created by two celestial bodies and the Earth: Opposition means the two bodies are on opposite sides of the Earth, while conjunction means that one body is between the Earth and another body.
How often do planetary alignments occur?
More often than you might expect! We can usually see at least one planet just about every night, and we regularly see two or three at various points during the year. When it comes to four or more planets in the night sky, that’s a bit less common, occurring every few years or so.
But we happen to be in something of a hotspot for planetary parades right now. In 2025, we’ve already had our January planet party, and February’s is happening now. “In mid-August, we’ll get six lined up in the morning sky: Jupiter, Venus, Uranus, Saturn, Neptune and Mercury,” says van Belle. (It’s worth noting that Uranus and Neptune are too faint to see with the naked eye, so you’ll need binoculars or a telescope to see them.)
Myths and hypotheses about planetary alignments
For millennia, humans have linked planetary alignments to major Earth-based events like natural disasters, but there’s no correlation. “Ancient cultures tried to draw inferences between the events in the night sky and forecasting the future,” says van Belle. Sometimes, it worked. The movement of constellations, for example, heralds the change of seasons, and thus can be used as an agricultural calendar.
Planetary alignments, however, don’t have any major physical effect on Earth. “The gravitational forces between the planets, including Earth, are negligible,” says van Belle. “The only noteworthy effect is the moon’s effect upon the tides.”
That said, some scientists hypothesize that planetary alignments might impact solar activity. A 2024 paper in the journal Solar Physics, for example, posits that the alignment of Venus, Earth and Jupiter could create a phenomenon called Rossby waves in the sun that drive the 11-year solar cycle. Is it possible? There’s always a chance, even if it’s a small one. But there needs to be much more research to prove it.
“A significant complication is that very long time periods — in certain cases, hundreds of years — are required to fully study the interactions of these effects of gravitation interaction between the sun and the planets,” says van Belle.
When planetary alignments matter
In the early days of the solar system, planetary alignments were much more significant than they are now. “The orbits of the planets hadn’t settled into the stable configurations we have now, and a considerable bit of ‘orbital migration‘ is thought to have taken place,” says van Belle. “Certain models even suggest that a fifth gas giant was ejected from the solar system, now a ‘rogue planet’, doomed to forever wander the empty void between the stars.”
But today, there is one very important use of planetary alignment. Various interplanetary spacecraft can use the specific positioning of planets to perform gravity assists, effectively slingshotting them with a speed boost toward their final destination.
“A good example is the New Horizons spacecraft, which got a gravity assist from Jupiter to speed it onwards towards Pluto,” says van Belle. “The Voyagers 1 and 2 took advantage of an alignment of the large planets, with Voyager 2 getting boosts from Jupiter, Saturn, Uranus and Neptune.”
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