Ever so often, you hear news about planetary alignments in the sky, and there is a good reason for it – several of the brightest planets are appearing to be aligned in the sky, or IN LINE with each other so to speak.
Are they anything major or special – astronomically speaking? Not really. However, they are fun targets for wide angle astrophotography, and are easy to observe as one doesn’t need a telescope to enjoy them, and they often have windows that last more than a few days for one to observe thus one won’t feel too bad if they miss out on a night.
Here we will talk about what’s actually happening and why they appear the way they do.
I cannot tell you how many visitors came up to the Observatory and ask me about a “planetary alignment” going on. This was especially during a notable ongoing one in the month of April 2022. Many people would just hear the words, not bother to look up when and how to observe it, and thus come up hoping to see it during the evening viewing hours only for me to tell them “sorry, it’s visible at 5am before sunrise!”
Either way, we know that events like these are easy to get attention, and people like me are happy to explain the truth behind how these “planetary alignments” work.
So What’s Going On?
Remember that the Sun has a “path” across the sky which we call the Ecliptic. The planets also usually appear along this path at any given point, and it’s all due to each planet, including Earth, all having the same orbital plane with a few minor tilt differences in relation to the Sun. You can see an example of this in the following image.
And BECAUSE they share that same orbital plane, they sometimes appear “in line” due to their respective orbital positions around our Sun as seen from Earth. They are not actually all “aligned” with Earth, nor in the same order in the Solar System as you see from Earth in these following pictures.
In late April of 2022, one could see four of the five naked eye planets in the morning sky. The images above are from April 20. While they do appear in line from Earth, in reality, here is the positions as they were in the solar system.
As you can now see… even though Jupiter appears closest to the Sun (or where it would be in the sky before sunrise), it’s actually “third” in that order in terms of distance, and neither Saturn nor Jupiter are in line with Venus or Mars. In reality, we see this formation because all four of these planets are on that side of the Solar System. As they continue their orbits, the four planets in the 4/20/2022 pictures will gradually shift in two ways – one from appearing closer or further from each other in the sky, and two – from being morning targets into becoming evening targets after a few months. If one sees a formation like this in the evening, then the same happens, only they will shift into morning targets a few months from then.
That should help explain to you what actually is going on, and how many of these so called “alignments” are not actually true alignments. But when you see three to four of them along the same side of the sky in a relatively tight order, we still enjoy the sight when they appear like jewels in a cosmic necklace, especially when the moon joins them as a centerpiece.
It’s even more rare when you have all five of the naked eye planets appearing on the same side, as that usually happens every half century or so on average, with the last time being in 2002, and the next time being on September 6, 2040. This is due to Mercury’s fast 88 day orbit and its closer position to the Sun making it difficult to spot in the sky on most nights.
If All 8 planets were truly in line with each other in the Solar System – like how one sees in left-right diagrams in the order of Sun through Neptune:
- Observers on the day side of Earth would see Mercury and Venus transit across the Sun simultaneously…
- Observers on the night side of Earth would see Mars, Jupiter, Saturn with the naked eye, plus Uranus and Neptune, all appear at opposition (rise at sunset, cross meridian at local midnight, set at sunrise), and appear so tightly positioned that one could cover all of them with their thumbs!
- NOTHING like this has ever happened in recorded history!