Planet Parade: How to see it in the night sky?
In this article, we’ll tell you everything you need to know about a breathtaking astronomical event called planetary parade and inform you of the next planetary alignment.
- What is a planet parade?
- Types of planetary parades
- When do the planets align?
- What happens when the planets align?
- When was the last time all the planets aligned?
- When will the next large planetary alignment occur?
What is a planet parade?
Although there is no official scientific term ‘planetary parade’, it is widely used in astronomy to denote an astronomical event that takes place when planets of the Solar System line up in a row in the same area of the sky, as seen by observers from Earth. There is no single definition of this phenomenon. These are the three most commonly used:
- An astronomical event that occurs when planets line up in a row on one side of the Sun at the same time, as seen up above the plane of our Solar System. How often do the planets align? Three planets align on one side of the Sun simultaneously two times a year, four planets – once a year, five planets – once in every nineteen years, and all eight planets of the Solar System – once in about one hundred seventy years.
- A visual phenomenon that occurs when planets of the Solar System appear in a small sector of the sky at the same time regardless of their visibility conditions, from Earth's point of view (as seen by observers from Earth). A planet parade of this type happened on April 18, 2002, when all planets of the Solar System that are visible to the naked eye lined up in a row in the evening sky. According to preliminary forecasts, such planet parades will take place in July 2020, in March and June of 2022, in 2040 and 2854.
- On rare occasions, there are very good seeing conditions of all planets of the Solar System in one night. These events are also referred to as planet parades. For inner planets, the best viewing conditions occur near the greatest elongations, and for outer planets – sometime before and after oppositions.
Types of planetary parades
Another term for a planet parade is ‘appulse’. The following types of planetary parades are distinguished according to the number of participating planets:
- Mini planet parade – 3 planets.
- Small planet parade – 4 planets.
- Large planet parade – 5 or 6 planets.
- Great (full) planet parade – all Solar System’s planets (+ Pluto sometimes).
Mini planet parades are not rare events. Three planets can be simultaneously observed in the same part of the sky several times a year.
When do the planets align?
It is important to point out that planetary alignment during a planet parade should not be taken literally. In reality, planets never align in one perfectly straight line, as usually shown in the pictures. Since the Solar System’s planets do not all orbit perfectly in the same plane and swing about on different orbits in three-dimensional space, they will never be perfectly lined up.
What happens when the planets align?
By planets’ alignment or parade, astronomers usually mean that planets will appear in the same part of the sky. Sometimes the arrangement of planets in the sky resembles a line, but it's not always the case. Most often, two or three planets form a line in the sky.
Besides, a lot depends on the viewpoint. When planets line up on one side of the Sun, they are not necessarily in the same region of the sky for observers from Earth. Vice versa, when planets are in the same part of the sky from Earth's point of view, they are not necessarily aligned from the point of view of the Sun.
When was the last time all the planets aligned?
On July 4, 2020, a rare and unique planet parade took place. All the planets of the Solar System – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune plus the dwarf planet Pluto – lined up on one side of the Sun at the same time. This was a planet parade of the first type of the three described above. The near-perfect alignment didn’t occur, as the deviation angle was quite small. Before that, the parade of planets of this type happened in 1982, and the next one is expected in 2161.
Also, in August 2020, the planetary parade of the third type occurred: observers could witness all the planets in one night. At the beginning of the month, the elusive planet Mercury shone in the morning sky, and brilliant Venus was sitting nearby. The red planet Mars, distant Uranus, and Neptune, all approaching their oppositions, were well placed for observation, as well as the gas giants Jupiter and Saturn. Even the dim dwarf planet Pluto offered skywatchers favorable conditions for viewing it due to its opposition.
When will the next large planetary alignment occur?
The stargazers will have a chance to enjoy the breathtaking planetary parade of the second type in March 2022: five planets of the Solar System – Mercury, Venus, Mars, Jupiter, Saturn – will simultaneously appear in a small sector of the sky. However, the observing conditions that month will be unfavorable for astronomy lovers from some parts of the globe. If you miss out on the planet parade in March, try your luck in June 2022, when one more alignment of planets will occur.
If you would like to check the time of planetary alignment for your location and to easily locate planets on the sky's dome, consult the stargazing app Star Walk 2. Turn the app's notifications on to be notified about the most noteworthy astronomical events in time.
Let's briefly recap all the information about planetary parades given above – just in case you don't feel like reading a long article.
What is a planetary parade?
It is an astronomical event that occurs when the Solar System’s planets line up in a row in the same area of the sky, as seen from Earth. The astronomical events that can be referred to as planet parades include:
- events that take place when planets align in a row on one side of the Sun at the same time, as observed up above the plane of the Solar System;
- visual phenomena that happen when the planets of the Solar System appear in a small sector of the sky at the same time, as seen by a terrestrial observer,
- nights when all planets of the Solar System can be seen.
What types of planet parades are there?
There are four types of planet parades: mini (3 planets), small (4 planets), large (5 or 6 planets), and great (all Solar System's planets).
When do the planets of the Solar System line up?
In reality, the Solar System’s planets never align in one perfectly straight line, as they do not orbit in the same plane.
What to expect from a planet parade?
During this spectacular event, you can see planets lined up (or just gathered) in the same part of the sky.
When was the last time a planetary parade occurred?
All the planets of the Solar System lined up on one side of the Sun at the same time on July 4, 2020. Also, the next month observers could see all the planets in one night.
When to see the next large planetary parade?
In March 2022, five planets of the Solar System will simultaneously appear in a small sector of the sky. In June 2022, one more planetary alignment will occur.
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