An exceptional lineup of four planets (and the Moon) in April 2022

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Notice of observation of a fascinating astronomical event: a parade of four planets through the sky of the northern hemisphere. It is the alignment of several planets of the solar system in the same area of ​​the sky, from the point of view of terrestrial observers. Between April 17 and 30 there will be an alignment of four planets: Jupiter, Venus, Mars and Saturn will form a straight line in our sky. This phenomenon will be visible to the naked eye at sunrise and will peak on the morning of April 20. During the second half of June, this alignment will be repeated with Mercury in addition.

It is true that it is possible to observe three planets simultaneously in the same area of ​​the sky several times a year. Mini-planetarium parades are not uncommon events. But major planetary alignments like this, visible to the naked eye, are very rare and have only happened three times since 2005. Michelle Nichols of the Adler Planetarium in Chicago says: ” We don’t always have that opportunity. Sometimes it’s one or two planets in the sky; often nothing ».

In fact, for example, on July 4, 2020, a rare alignment of planets occurred. All the planets of the solar system (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and the dwarf planet Pluto) were visible simultaneously, although the alignment on the same side of the Sun was not perfect: but the angle of deviation was small. Before that, the last such alignment was in 1982, and the next one is expected in 2161.

End of a planetary ballet

As amateur astronomers probably already know, Saturn, Mars and Venus have been regrouping since the end of March, but it is only in mid-April that Jupiter will join them. In fact, an hour before local sunrise time, Venus, Mars, and Saturn form a narrow triangle on the southeastern horizon. On March 27 and 28, the last crescent Moon completed this planetary encounter.

Observers who follow the planets from day to day noticed a change in their position. The planets form a triangle whose angles gradually evolved until April 1, when the trio appeared in a straight line. Saturn could be seen approaching Mars in early April, until the two stars appeared side by side between April 3 and 5. On April 4, the two planets were only half a degree apart, the diameter of the full moon. Around April 17, Jupiter will join the line of Venus, Mars and Saturn. A few days later, around April 23, the lineup should become even more dramatic, with the Moon ending the line. It will appear to the right and above Saturn, before disappearing on April 29, when it appears too close to the sun to be seen. The Moon will rejoin the planetary lineup again beginning May 21.

Representation of the alignment of the four planets and the Moon on April 23, 2022. © Stellarium

To see them, you’ll have to be in flat, open space, to see Jupiter, which will be much lower in the sky than the other planets, and low. contamination shiny. To distinguish planets from surrounding stars, constant light must be sought. Michelle Nichols explains: The light from the planets is less affected by the Earth’s atmosphere than the light from the stars.. The general rule is that stars twinkle, planets don’t. ».

Sky chart showing the alignment of the four planets before sunrise on April 30. © NASA/JPL-Caltech

matter of perspective

When celestial bodies line up like this, it only happens in Earth’s sky, of course. Seen from a different place in space, the position of each planet would be completely different. In fact, the planets are not really aligned in space; alignments are a trick of perspective.

The planets revolve around the sun in a flat plane, so when they pass by each other, from Earth’s perspective, they appear to be aligned. An observer looking at the solar system from above would not see straight lines. Mercury revolves around the Sun every 88 Earth days, Venus every 225 days, Mars every 687 days, Jupiter every 12 years, and Saturn every 29 years. Given these varied timelines, the planets’ orbits bring them together at irregular intervals, making this alignment an exceptional and rare event.

Next meeting in June

In June, early risers will be able to see a rare lineup of the major naked-eye planets: Mercury, Venus, Mars, Jupiter, Saturn, and perhaps even Uranus under ideal conditions. In addition, the Moon will transit close to each planet between June 18 and 27. This alignment will cover more of the sky than in April, making it difficult to discern or photograph.

On June 24 and 25, the last crescent Moon will rub shoulders with Uranus and will facilitate its observation, especially with binoculars. Under the right conditions, Uranus will therefore be visible as a small point of green light in the sky. Regulars will be able to watch the Moon meet Venus on June 26, then Mercury on June 27, when the two stars appear to merge at sunrise.

Being a rare astronomical event, from a terrestrial perspective, Michelle Nichols advises: You need to set your alarm, it’s just a fun time to go see planets in the sky and learn what they look like. So grab your binoculars!

Source : POT

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