An extraordinary alignment of four planets (and the moon) in April 2022

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Note the observation of an intriguing astronomical event: a parade of four planets in the northern hemisphere sky. It is the alignment of several planets of the solar system in the same area of ​​the sky as seen by terrestrial observers. Between April 17th and April 30th 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 dawn and will peak on the morning of April 20th. In the second half of June, this alignment is repeated with Mercury.

Granted, it is possible to observe three planets simultaneously in the same area of ​​the sky several times a year. Mini planetary parades are not uncommon occurrences. But major planetary alignments like this, visible to the naked eye, are very rare, having only happened three times since 2005. Michelle Nichols of the Adler Planetarium in Chicago says: ” We don’t always have that option. Sometimes there is a planet or two in the sky; often it is nothing “.

Indeed, on July 4th, 2020, for example, a rare alignment of planets occurred. All the planets in the solar system (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and the dwarf planet Pluto) were visible at the same time, 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 is expected in 2161.

End of a planetary ballet

As amateur astronomers probably already know, Saturn, Mars, and Venus have been converging since late March, but Jupiter won’t join until mid-April. Indeed, Venus, Mars, and Saturn form a tight triangle above the southeastern horizon an hour before local sunrise time. On March 27th and 28th the last crescent moon completed this planetary meeting.

Observers who follow the planets from day to day then noticed a change in their position. The planets form a triangle, the angles of which gradually developed until April 1 when the trio appeared in a straight line. In early April, Saturn could be seen approaching Mars until the two stars appeared side-by-side between April 3rd and 5th. On April 4, only half a degree separated the two planets, the diameter of the full moon. Around April 17, Jupiter will join the series of Venus, Mars and Saturn. A few days later, around April 23, the alignment should become even more dramatic as the moon ends the line. It appears 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 planetary alignment beginning May 21st.

Showing the alignment of the four planets and the moon on April 23, 2022. © Stellarium

To see them you need to be in flat, open space – to see Jupiter, which is much lower in the sky than the other planets – and with little light pollution. To distinguish the planets from the surrounding stars, one must look for constant light. Michelle Nichols explains: Light from planets is less affected by the Earth’s atmosphere than light from stars. The general rule is that stars twinkle, planets don’t. “.

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

question of perspective

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

The planets revolve around the Sun on a flat plane, so when they pass side by side they appear to be aligned from Earth’s perspective. An observer looking at the solar system from above would not see straight lines. Mercury orbits 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 divergent timelines, the planets’ orbits bring them together at irregular intervals, making this alignment an extraordinary and rare event.

Next meeting in June

In June, early risers can see a rare alignment of the major planets visible to the naked eye: Mercury, Venus, Mars, Jupiter, Saturn and maybe even Uranus in ideal conditions. Also, the moon will pass close to each planet between June 18th and June 27th. This alignment will encompass more of the sky than April, making it harder to spot or photograph.

On June 24th and 25th, the last crescent moon will be next to Uranus, making it easier to observe, especially with binoculars. Therefore, under the right conditions, Uranus will be visible as a tiny point of green light in the sky. The more diligent can then watch the Moon’s rendezvous with Venus on June 26 and then Mercury on June 27 when the two stars appear to merge at dawn.

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

Source: NASA

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