Planetary Parade: What this phenomenon might look like in other worlds (photos)

On February 28, with a clear and dark sky, there will be an opportunity to witness a very rare planetary parade after sunset. That evening, 7 planets of the Solar System will align in a row forming an arc. This event will not occur again for another 15 years. But what would such a planetary parade look like from the surface of Jupiter’s moon Europa or one of the planets in the fascinating TRAPPIST-1 system? This is discussed by Space.

What is often referred to as a planetary parade is actually a planetary alignment, where several planets of the Solar System can be seen in a row from Earth, arranged in an arc.

All planets orbit the Sun in a single plane, which astronomers call the ecliptic. As they move along their orbits, the distances between each pair of planets increase and decrease. When we look at the night sky, the brightness of the planets depends on how close they are at that moment.

On February 28, the 7 planets of the Solar System—Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune—will be close enough to Earth for most of them to be visible to the naked eye.

In the Solar System, besides Earth, there are three other rocky planets—Venus, Mercury, and Mars. Additionally, rocky moons orbit around the larger planets. This indicates that the surfaces of these worlds are solid. One of the most intriguing moons of Jupiter is Europa, which scientists believe conceals an ocean beneath its icy surface, containing more water than all of Earth’s oceans combined.

If humans had emerged not on Earth but on Europa, what would we see in the night sky during the planetary parade? In fact, we would never be able to see all 7 planets aligned in the night sky. From Jupiter's moon, Mercury would be impossible to see with the naked eye.

When observing from Europa, the night sky looks quite different than it does from Earth. Firstly, Jupiter would appear 20 times larger than the Moon does in our sky. Moreover, one of Jupiter's main features, the atmospheric vortex known as the Great Red Spot, would appear larger than the Sun. Strange as it may sound, the Sun would only look like a dim orange spot, appearing 5 times smaller than it does when viewed from Earth.

Currently, astronomers are aware of thousands of planets located beyond the Solar System. What would a planetary parade look like on one of those planets if humans had emerged there? For instance, on one of the seven planets orbiting the nearby star TRAPPIST-1. This red dwarf is smaller and cooler than the Sun, and all the planets orbit it at distances that fit within Mercury's orbit—the closest planet to the Sun.

Since these planets orbit so close to the star, each of them revolves around TRAPPIST-1 much faster than it takes Earth to orbit the Sun.

If humans existed on the rocky planet TRAPPIST-1 b, which is closest to the star, we could witness the parade of the six other planets every few days. This planetary alignment would be far more thrilling than anything visible from Earth.

We would see the red dwarf TRAPPIST-1 appearing 10 times larger than the Sun does from Earth. Additionally, we could observe the planets disappearing behind the red dwarf, and then every few days they would become larger than the Moon in our sky.