Planetary Alignments Hype

by Dr Paul E Cizdziel

My knowledge of astronomy is nearly all self-taught over the last 5 to 10 years.  It was a surprising migration of my scientific interests from a career in bioscience to a late-in-life fascination with the universe around us.    

One of the common questions I get is about “planetary alignments” which seem to be hyped-content frequently observed on social media sites, like YouTube.  Sensationalized titles like “One in a Thousand Year Planetary Alignment” are typical click-bait phrases to capture views.   Although the content on these artificial-intelligence (AI)-generated videos is usually pretty accurate, it does not often match the sensationalized title. 

Image is courtesy of the Secrets of the Universe YouTube channel.

The truth about planetary alignments is that the planets are always aligned in the sky.  In the formation of our solar system 4 to 5 billion years ago, gravity created a swirling mass of gas and dust that coalesced into our sun and orbiting planets.  This phenomenon naturally generates planets that all orbit the central star along a flat plane, that we call the ecliptic.   Today, after 4.6 billion years, the planets are still roughly aligned on this same plane, all orbiting the sun in the same direction.  And because the earth is inclined on its rotational axis relative to this plane, if you look into the night sky, you can see that all the planets follow along the same arc-line as they traverse across the sky each night.   That arc line is the ecliptic described earlier.   Essentially, they have been in alignment; since the beginning of the solar system!   

Relative to the East to West movement of the stars (caused by the rotation of the earth), the planets move at slightly slower rates (retrograde motion is an exception).  Relative to the fixed celestial star-field, the change in position of Mars and Jupiter is more noticeable because they are closer to us.  These two planets seem to occasionally overtake others that are further away like Saturn and Uranus and Neptune.  And Mercury and Venus are always seen in the morning or evening only, since they orbit close to the sun from our perspective. 

It happens fairly frequently that multiple planets can be observed relatively near to one another along the ecliptic in the night sky.   This is usually what gets hyped in social media; but it is fairly common and subjective (e.g. what is close in the sky?).   

When two planets are very close, such as they can be seen together in a single field of view of a telescope or binoculars, the event is referred to as a “conjunction” or more accurately an “appulsus”.   It may last for a few nights until they drift apart again.  In three dimensions, this event is when a planet passes more-or-less directly between the earth and another more distant planet (or object).

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A note from our Science Advisor, Dr Paul E Cizdziel

The Ad Astra room on the 10th floor of Laurus International Primary & Secondary School is primarily dedicated to space science education, an increasingly important part of modern education. This field of science covers everything from amateur photographers (like myself), to aerospace engineering, government agencies, research institutions, and a rapidly expanding and opportunity-rich commercial sector. My intention with this blog is to periodically provide information of general interest to students and parents on current topics across all these categories.