A Case of Cometosis

Every so often I get this affliction I’ve had several times in my life, and hope to have several more times in the future. It’s called “cometosis”.

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The first symptom I noticed was a bit of nervous anxiety, a twinge here and there, mostly at night looking at an overcast sky.  The gloom of the vast stretch of clouds matched my mood, and after only a few hours of sleep there I was again staring skyward at a dark sea of never ending vapors.  I recognized the symptoms immediately.  It’s an affliction I’ve had several times in my life, and hope to have several more times in the future.  It’s called “cometosis”.

These are a few of my favourite things

One of the things I like about astronomy is that it’s so predictable.  We know exactly when and where to find all kinds of objects: stars, planets, galaxies, asteroids, etc. and also the timings of really cool events such as: eclipses, meteor showers, transits and the like so we can plan accordingly and never miss a thing.  One of the other things I like about astronomy is how unpredictable it is.  There are things that happen in the sky without notice like fireballs, solar flares, novae, aurora, and bright comets.

The word comet means “hairy” star due to the fuzzy nature of the object, and its tail appearing as a beard emanating from a star-like coma.  It also has been thought of historically as the angel of death.  There was something disconcerting in seeing the bright tail of a comet hanging in the twilight like a fiery sword moving slowly across the sky night after night.  They were considered evil omens; something horrible would happen if you saw a bright comet.  So I suppose that with all of the craziness of 2020, it would be appropriate for a bright comet to grace our sky.  Exactly what this year needs!

What’s in a comet?

Actually a comet is nothing more than a collection of ice and rock.  As it gets close to the sun and melts, this icy dust billows around the nucleus creating what is called the coma.  We never see the irregular nucleus of a comet through a telescope, what we see is the bright round coma.   Particles streaming away from the Sun, called the solar wind, ionize volatile gases in the coma and push them away in a long straight electric blue tail.  Astronomers call it the ion tail or plasma tail.  This tail always points away from the Sun. 

The solar wind also pushes the icy dust away from the comet, and as the comet moves it leaves this trail of ice and dust behind which is yellowish in color, and called appropriately enough the dust tail.  The dust tail points away from the comets motion.  The more a comet melts the brighter it gets, but most comets don’t melt very well, and therefore don’t develop a tail at all.

That wasn’t the case for C/2020 F3 NEOWISE.  The comet was discovered on March 27, 2020 by the NEOWISE Space Telescope, and its path around the Sun in late June allowed the comet to brighten significantly.  Northern observers were thrilled to see the comet with the naked eye hanging low in the sky in early July.

A bad case of cometosis

The clouds hung solid over my sky for almost the first dozen days of the month, but early on the morning of July 12 at 4:20 AM, I saw the comet clearly with just my eyes.  There it was above the trees, a very bright coma with a faint tail jutting gloriously skyward.  Through binoculars it was absolutely spectacular as you could see individual strands of material suspended in the tail.  The longest exposure I could get was only 10 seconds before the sky brightness overexposed the predawn image.  With a DSLR camera hooked up to a telescope and another DSLR hooked up to a 75mm camera lens, I was able to get two different views of the cosmic interloper.  I also sketched it through binoculars.   At that moment I knew I had a full blown case of cometosis.

Cometosis is rarely fatal.  Symptoms include having my time shifted to accommodate comet viewing no matter what time of night it appears, and all astronomical equipment is revamped for comet observations.   By July 13 it could be seen briefly in the early evening, and then again around 3:30 in the morning.  Different telescope and camera lens combinations are utilized, and longer exposures are possible as it stays in the dark sky longer.   The effects of cometosis usually dissipate as the object grows fainter once it moves beyond the orbit of Mars. 

What next?

As I write this the clouds have once again cycled around to our sky, but I’ll still get up around 3:30 AM to look out to make certain the sky is overcast.  The comet has also become noticeably fainter this past week.  And although I no longer have “teenage eyes” it no longer appears as a visible object, but it is still spectacular through binoculars.  The difference now is that you really need to know exactly where to look.  And as with most things seeing is believing, so I imagine the public interest will start to wane, but Comet F3 NEOWISE has made an impact.

Photo Peter Detterline

Perhaps not on the Earth itself (thank goodness), but certainly to the people who have observed it shining brightly in the predawn sky.  The comet reminds us of how unpredictable, how beautiful, how rare, how amazing the universe can be.  It reminds us to be humble, as we think of our place in the solar system and the universe at large.  It has given us a respite from the COVID 19 news, and has gotten people who normally don’t strain their necks skyward to keep looking up!  And perhaps that’s the best thing we can all do in 2020.