The moon is lining up to lead a parade of planets across the predawn sky starting April 23.
In advance of an unusual alignment of the five visible planets in the solar system, four planets are lining up behind the moon like ducks in a row. On April 23, Saturn, Mars, Venus and Jupiter will all be visible above the horizon in the early morning hours in the northern hemisphere.
Mercury will join this parade of planets in mid-June.
When the planets align
Planetary alignments occur when the planets’ orbits bring them to the same region of the sky, when viewed from Earth. These planetary alignments are not rare, but they’re not regularly occurring, either: The last time five planets aligned in the night sky was in 2020, preceded by alignments in 2016 and 2005.
These alignments take time to develop. Venus, Mars, and Saturn have been night-sky neighbors since late March. On April 4 and 5, they came so close together, when viewed from Earth, that Mars and Saturn appeared less far apart than the width of the full moon in the southeast early morning sky.
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Jupiter turned the trio into a foursome in mid-April. The moon will appear in its last quarter phase to Saturn’s right on April 23. Mars will be an orange dot below and to the left of Saturn, while Venus will be a brighter light below and to the left of Mars. Jupiter will be lowest and leftmost in the sky.
The way to tell the planets from the stars in the sky is by the light, said Michelle Nichols, the director of public observing at Chicago’s Adler Planetarium.
“Stars twinkle,” Nichols told Live Science. “Planets don’t.”
Watching the planetary alignment
The planets will be most visible in the northern hemisphere an hour to 45 minutes before sunrise. The moon will remain above the horizon until April 29, but the four planets will remain in their cosmic line until early July. Mercury will appear in the line as early as June 10 in places with a flat, eastern horizon (think Denver or the coast of North Carolina, looking out over the ocean), leading to the final five-planet alignment. The planets will appear to march from the east to the south, Nichols said. Late June will provide the best viewing conditions for the alignment.
Uranus and Neptune will also be in the field of view in the Northern Hemisphere during the alignment. Uranus will be between Mercury and Mars and will be visible in areas without much light pollution. It might be possible to see it with the naked eye in a dark-enough sky, but binoculars will aid in observing it, Nichols said. Neptune will require a telescope to view.
“It’s just a great time to go out and see the planets,” Nichols said.
Originally published on Live Science