© Getty Images

Rare event -

On February 28, seven planets were visible: Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune, producing a rare seven-planet alignment.

© Getty Images

How it works -

Planet alignments are rare, but they happen because the eight major planets of our solar system orbit the Sun on the same flat plane, but at different speeds.

© Shutterstock

From time to time -

This means that every now and again, multiple planets line up on the same side of the Sun. If they are not perfectly aligned, the planets appear in an arc.

© Shutterstock

Beautiful and meaningful -

For people interested in astronomy, planet alignments are a sight to behold. However, they also have scientific implications.

© Shutterstock

Potential impact on solar activity -

In 2019, for example, researchers suggested that planet alignments may have an impact on solar activity, due to the way they combine the planets’ tidal forces.

© Shutterstock

Combined tidal pull -

The tidal pull of an individual planet on the Sun is very small. When combined, however, researchers believe that their pull may cause small rotations within the Sun.

© Shutterstock

Rossby waves -

These rotations are referred to as Rossby waves, and we also see them on Earth, where they cause extreme weather events such as cyclones and anticyclones.

© Shutterstock

Solar activity cycle -

Some scientists believe that in the Sun, Rossby waves may provide an explanation for why the Sun works on an 11-year cycle that goes from peak activity to low activity.

© Shutterstock

Not universally accepted -

However, not every expert is convinced by this hypothesis. Indeed, many believe that solar activity can be explained by processes in the Sun alone.

© Shutterstock

Other implications -

A less contentious implication of planetary alignments is that they can be used to visit multiple different planets in a relatively short period of time.

© Shutterstock

Visiting distant planets -

In general, reaching the outer planets with a spacecraft is difficult because they are so far away that they would take decades to reach.

© Shutterstock

1966 discovery -

In 1966, however, a NASA scientist worked out that a planetary alignment of Jupiter, Saturn, Uranus, and Neptune in 1977 would allow astronauts to visit all four planets in just 12 years.

© Getty Images

Seizing the opportunity -

Given that the same voyage would take 30 years if the planets were not aligned, NASA scientists seized on the opportunity.

© Getty Images

The Grand Tour -

In 1977, they launched the twin Voyager 1 and 2 spacecraft on a so-called "Grand Tour" of the outer solar system.

© Getty Images

Unchartered territory -

Voyager 2 was the most successful. It used the alignment to visit all four planets, and became the first spacecraft ever to visit Uranus and Neptune.

© Shutterstock

Outside our solar system -

Planetary alignments are also useful for learning about what goes on outside of our own solar system. In particular, they help us discover exoplanets (a planet that orbits a star other than our Sun).

© Shutterstock

Discovering exoplanets -

When an exoplanet passes in front of its star from our point of view, it dims the light of the star, allowing for the planet’s size and orbit to be discerned.

© Shutterstock

The transit method -

This method of discovering an exoplanet is called the transit method, and it has been used to discover many exoplanets in orbit around certain stars.

© Shutterstock

Studying Trappist-1 -

For example, it is thanks to the transit method that we know there are seven Earth-sized planets orbiting Trappist-1, a red dwarf star that is located 40 light-years from our planet.

© Shutterstock

Atmospheric analysis -

Transits can also be used to study the atmosphere on the exoplanets themselves. Indeed, when a planet passes in front of a star, the star’s light goes through the planet.

© Shutterstock

How it works -

Given that the molecules and atoms of different gases absorb the star’s light at different wavelengths, this allows for gases such as carbon dioxide and oxygen to be identified.

© Shutterstock

Useful tool -

Indeed, scientists owe a lot of their atmospheric composition analyses and the learnings therefrom to planetary alignments.

© Shutterstock

Larger scale alignments -

Alignments on a much larger scale, namely the alignment of galaxies, can even help scientists learn about the early universe.

© Shutterstock

Observing the early universe -

In general, it is very difficult to observe galaxies in the early universe because they are so faint and distant.

© Shutterstock

Huge pull -

However, if a large galaxy, or even a cluster of galaxies, passes between us and a much more distant galaxy, its huge gravitational pull can magnify the light of the more distant object.

© Shutterstock

Gravitational lensing -

This process is called gravitational lensing, and it allows us to observe and study the farther away of the two galaxies.

© Shutterstock

The James Webb Space Telescope -

The work on these huge alignments is done by telescopes such as the James Webb Space Telescope.

© Shutterstock

Earendel -

This telescope is used to observe and study distant stars and galaxies, such as Earendel, the furthest known star from planet Earth.

© Shutterstock

Earendel -

The light from Earendel came from the first billion years of the 13.7-billion-year history of the universe, and it was only visible thanks to gravitational lensing.

Sources: (BBC)

See also: Stellar spectacular: NASA photos that will make you feel small

© Shutterstock