Seven planets are lining up in the sky next month. This is what it really means

 

Stargazers will be treated to a rare alignment of seven planets on 28 February when Mercury joins six other planets that are already visible in the night sky. Here's why it matters to scientists.

Peer up at the sky on a clear night this January and February and you could be in for a treat. Six planets – Venus, Mars, Jupiter, Saturn, Uranus and Neptune – are currently visible in the night sky. During just one night in late February, they will be joined by Mercury, a rare seven-planet alignment visible in the sky.

But such events are not just a spectacle for stargazers – they can also have a real impact on our Solar System and offer the potential to gain new insights into our place within it.

The eight major planets of our Solar System orbit the Sun in the same flat plane, and all at different speeds. Mercury, the closest planet to the Sun, completes an orbit – a year for the planet – in 88 days. Earth's year, of course, is 365 days, while at the upper end, Neptune takes a whopping 60,190 days, or about 165 Earth years, to complete a single revolution of our star.

"There is something special about looking at the planets with your own eyes," says Jenifer Millard, a science communicator and astronomer at Fifth Star Labs in the UK. "Yes, you can go on Google and get a more spectacular view of all these planets. But when you're looking at these objects, these are photons that have travelled millions or billions of miles through space to hit your retinas."

Much grander alignments can let us probe the distant Universe, namely the alignments of galaxies. Observing galaxies in the very early universe is difficult because they are so faint and far away. However, if a large galaxy or cluster of galaxies passes between our line of sight with a much more distant early galaxy, its large gravitational pull can magnify the light of the more distant object, allowing us to observe and study it, a process called gravitational lensing.

"These are huge alignments across the scale of the universe," says Christiansen. They are used by telescopes such as the James Webb Space Telescope to observe remote stars and galaxies such as Earendel, the most distant known star from Earth. The light viewed by the telescope from the star came from the first billion years of the 13.7-billion-year-history of the Universe and was visible only because of gravitational lensing.

https://www.bbc.com/future/article/20250117-planetary-parade-what-the-alignment-of-seven-planets-really-means-for-science