The Unpredictable (and Disappointing) Nature of Comets – Editorial

Updated February 3, 2023 

It always happens… the news of a potential show stealer, or a “naked eye” level comet reaches the headlines and into the devices of the casual observers. Sometimes, a big deal is made about the particular color or how “rare” the comet actually is… And for many people it’s their FIRST comet that they’re hearing about – or so we learn from many curious patrons who call or visit the observatories and/or reach out to dedicated astro-observers. 

But then… uh oh… it’s NOT a naked eye level? Wait… you mean it’s not really that remarkable? What do you mean it’s not all that special?

Allow me to remind all the casual observers that more times than not, potential superstar or “great” comets almost always fizzle out and go out with a whimper rather than put on a stellar show for the ages!

So…if you’re experiencing the disappointment over C/2022 E3 (ZTF) not reaching naked eye level visibility on par with great comets of the past, trust me… you’re not alone!

If this is your first time experiencing the disappointment of a comet, then join the club!

Comets will ALWAYS have a special place in my heart!

For many people, comets like Hyakutake and Hale-Bopp were both the spark that got me into astronomy and inspired me to get a telescope. About 10 years later, hearing about Comet 17P/ Holmes having that bright outburst in activity was another spark that got me back into astronomy and cemented my passion towards the heavens for good. Comet 46P/ Wirtanen, the so-called “2018 Christmas Comet,” was the object that got me finally into astrophotography – it was the only way I could truly observe it!

Trust me, I understand that spark and mystique that comets bring! 

46P Loop
46P Looping Sequence

For Northern Hemisphere observers… it’s been almost 30 years since we had a showstopper, or “great comet.”

Comet NEOWISE in 2020 did come close for us in the northern hemisphere to be officially considered a “great comet” but ultimately the long tail was only visible to the naked eye from a dark location… from cities it could only be seen through optical aid or photography. Sadly, it disappointed the casual observers who didn’t have the sense to drive to a darker location to observe its full potential!

But that hasn’t stopped news of potential good shows over the years. But if you’re living through a disappointment because ZTF not being as good of a show as you expected… sorry to say that this won’t be the first time!

For many decades, astronomers have always been weary about raising awareness for potential great comets. If the internet wasn’t around, it’s quite possible the public could still miss out on them!

Are you over 50 and do you remember Comet West, the “Great Comet of 1976?” It was one of the brightest in history and could be observed in the daytime!


You don’t remember hearing about it? That’s because neither astronomers nor the media made any major fuss about it to the public, and you can blame the backlash and disappointment from the public over Comet Kohoutek.

The one on the left is Kohoutek – the predicted “Comet of the century.” The one on the right is West, a comet that went largely unreported due to fears of public backlash.

For those too young to remember, Kohoutek was a comet discovered in 1973 that was hyped to be the “Comet of the Century,” because of initial findings suggesting it being an Oort Cloud object visiting the inner solar system for the first time – hence a lot of outgassing from icy material that hasn’t been heated by the Sun yet. But that didn’t happen. Instead it never brightened to the expected levels, partially disintegrated as it got closer to the Sun, and by the time it was in a visible position at night, it was barely a naked eye object… if one observed from a location far from city lights…

Does That Sound familiar?

Another major example was 2013’s C/2012 S1 (ISON), which was predicted to be possibly brighter than the Moon at perihelion. But as it got closer, the brightening rate slowed down significantly, and never became bright enough for naked eye casual viewers – ultimately it disintegrated after perihelion in late November.

And once more in April 2020, Comet C/2019 Y4 (ATLAS), another comet that brightened at an alarming rate in March, ended up breaking apart and rapidly dimmed out of view. Even though I gladly imaged it, I remember telling eager people dont get your hopes up too much.” And sure enough, almost like it was on cue, the news broke out.

Unfortunately, those amazing comets that do impress us are the exception rather than the norm! For every Hale-Bopp or Comet McNaught, there’s dozens to perhaps hundreds of Kohoutek’s, and thousands more that are “never was'”. And the number of potential greats is literally just the tip of the iceberg to the number comets there actually are in our solar system!

On any given night, there are perhaps dozens of known comets in the sky, but they’re too dim for even modest sized telescopes to detect!

Even though we know what they are, and what causes them to brighten and put on their familiar displays, the science of predicting how much outgassing and brightening of any comet is still not quite there yet. No two comets behave the same way, even if they share similar orbital periods, and have similar properties. We know enough to know we don’t know everything.

Comet 67P/Churyumov–Gerasimenko as seen from the Rosetta Spacecraft on March 28, 2015

As comets get closer to the Sun, their frozen gases react to the increasing heat and create the comet that we see, thus comets get brighter and their tails get longer as they approach the Sun. Hence the predictions get made based on the rate of brightening over a select period. That sounds simple enough, right?

More times than not, however, the volatile material can vaporize from the heat when it’s further out, creating unrealistic expectations – and as we all know, many comets in recent years have done this. So that should tell the reader that it’s quite common for a comet to have a “burst” in brightness when it starts outgassing further out, but when the outgassing appears to plateau (flatten out) as it gets closer to our Sun, then that brightening rate slows down significantly.

The nucleus (the actual rock that’s only a few miles wide on average) becomes more unstable, and is prone to breaking apart when it deals with million degree Fahrenheit temperatures and solar winds!

Oh sure, sometimes comets do live up to the hype, and people like me would not have gotten into astronomy without them!

But most of the time they don’t. They could exhaust all of their icy materials that create the brilliant displays before they get close, and all we’re left with is a rock that swings around the Sun and barely makes a peep in the sky!

You can also blame light pollution, as comets that are deemed “naked eye” level but are not at the levels of bright stars and planets still require you to go to a dark location to glimpse them – and they look ghostly through a telescope. Many naked eye level comets, including that of Halley’s Comet’s notoriously disappointing 1986 appearance, would have been considered impressive or even “great” if light pollution didn’t wash them out! The same can be argued again for NEOWISE 2020.

Even if what we think going on is notable and exciting, as a former boss always used to tell me, “perception is reality.” Bad impressions are enough to turn people away and cause people to lose interest. Therefore, in the case of astronomy, it’s tough enough generating interest in celestial events like the appearance of a comet; so the last thing we want is to create a buzz around something that turns into a non-event for casual observers.

But wait… why does the media like to hype up “nothing” attributes?! You mean “green comets” aren’t that special?

Ah… So you’ve fallen victim to media overhype? Sorry, this won’t be the last time.

Keep in mind, there are over 3,700 comets that have been confirmed by humans since astronomers began studying and cataloging them, but there are perhaps BILLIONS that exist outside the orbits of Neptune that have yet to be detected.

New comets are being discovered each year because both amateur astronomers and professional observatories are always looking for them. There is always a very slim chance that I myself could stumble on an undiscovered comet while taking out observing or taking astrophotos, but I’m not holding my breath. Usually it’s an observatory team with array’s of telescopes and cameras that can survey the entire sky within a few days, as in the case of Zwicky Transient Facility at Mt. Palomar, CA – which is what “ZTF” stands for.

But they say this comet hasn’t been seen in thousands of years you say?

Actually… that’s actually the norm rather than the exception! Comets have much more eccentric orbits that take them further out of the solar system before returning. There are short period comets like Halley that return to the inner solar system every ~76 years… there are comets like Enke that take only 3.30 years to orbit the Sun… and then you have long period comets like Hale Bopp that take thousands of years before returning.

But… the color! It’s GREEN! I WANT TO SEE GREEN!

LOTS of comets exhibit a bluish green glow due to the nitrogen and diatomic carbon present in the outgassing. Almost every comet that I have taken a picture of since I began astrophotography in late 2018 has exhibited a green color on its coma!

Hmmm… notice a similar pattern? And this is one astro photographer out of millions who do the same!

And what the media often forgets to tell you is that in MOST cases, when observing the coma with binoculars or even a telescope with just your eyes, the comet will appear gray – not green or blue. In fact, the reason why I got into astrophotography and taking long exposure photos through my telescope was so I COULD see the color. This is due to differences in your human eye’s ability to see color on dim objects in the dark sky, versus a camera sensor which can be set to absorb enough light from the comet for the color to show. So yes… it is actually green or blue… but you won’t see the color unless you’re taking a long exposure photograph!

So why does the media like to make a big deal about its color? Or why do they like to add taglines such as “comet last seen by Neanderthals” in the case of C/2022 E3 (ZTF)?

It’s to generate interest in the casual viewer! If you’re a casual observer and reading this, would you have otherwise been interested in checking out the comet if you didn’t see the sugar coated headline? Chances are it would not have caught your eye. While that can be annoying we admit, at the end of the day we’re happy that there was interest generated.

Oh… and if you hear about anyone saying that a particular comet is a prophetic omen from the sky, or that its attributes like a second tail or anti-tail signify something bad or catastrophic for humans… scientifically speaking, that’s a big “NO” from this writer, and no modern astronomer in the 21st century will tell you otherwise!

So if you’re living with the disappointment of a comet for the first time, just remember we feel you too!

We always hope that the next time a comet makes the headlines that it will not disappoint. And we’re always sad if it does turn off potential new observers or interest in astronomy. But we’d rather there be interest generated than not at all! And you never know, that event could kickstart your journey!

Trust me, people like us WANT to see a bright comet – as they’re right up there with Total Solar Eclipses in terms of rarity and mystique, and we can’t wait for that next comet that gets everyone to go outside and look up, or possibly come visit a star party, an observatory and/or planetarium, and get their passion for astronomy ignited or renewed!

Support Your Neighborhood Astronomers!

You know where mainstream media sites get their information? From people like us! Support Your Neighborhood Astronomers! Everything is free, but donations help keep the website alive and go towards outreach events!



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s