If you bring a telescope and get away from city lights Friday evening, there’s a chance you’ll see seven planets parading through the sky.
Most of the planetary alignment, which is colloquially referred to as a planet parade, will be visible to the naked eye just after sunset Friday, according to Preston Dyches, writer and producer of NASA’s monthly sky-watching video series, “What’s Up.”
Mercury, Venus, Mars and Jupiter will be visible without a telescope Friday. Saturn will be faint and difficult to view. Uranus and Neptune require dark skies to be visible, and Mercury will have already set before it gets dark, meaning it won’t be possible to see all seven planets in an arc at one time, Dyches said.
What will be visible?
If you stay out into the night, it will be possible in the whole United States to have seen the planets within a six- or seven-hour time span.
Friday after sunset is ideal because Mercury – which had not popped above the horizon until late February – will be at its highest and brightest, said Dyches, who has worked at NASA’s Jet Propulsion Laboratory.
The only challenge will be spotting Saturn, which has almost dropped out of the horizon after being visible for months in the sky. Saturn may be faint and lost in the glow of sunset Friday, but that is also the best time to spot the second-largest planet in the solar system, he said.
“Maybe a very skilled observer with a clear view to the horizon would be able to find it with binoculars, but because of that difficulty, it’s not something you would call out as a target for general interest observers to go looking for,” Dyches said.
Why does it look like the planets are lined up?
The arc which the planets appear on is the plane of the solar system, Dyches said. They all move at different speeds – Mercury takes 88 of our days to orbit all the way around the sun, for example, while Neptune takes about 165 Earth years to do the same. As each planet follows its path at its own speed, they can appear for brief periods to line up next to each other from our perspective on Earth.
“We’re all on a racetrack together with the other planets,” he said. “As you look across, it’s like looking across the racetrack and other cars that are zipping around at different speeds than you.”
How rare of an event is this?
The remarkable aspect of this celestial event is attributed to luck and timing, according to Tracy Becker, a lead scientist at the Southwest Research Institute.
Usually, the planets are in different places all at once as they orbit the sun. The planet parade means that, for a certain amount of time, the orbits seem to align.
“We all just happen to be in the sky on this side of the sun at this time,” Becker said.