As Comet ATLAS Fizzles, Comet SWAN Arrives

The quest for comets and why great comets are so rare

July 14, 2020
Comet SWAN 2006
NASA

What’s the most spectacular sky object? A bright comet is certainly on my top-five list. A few weeks ago, you may have heard about Comet ATLAS. If not, no matter. It fizzled. And you’ll probably hear about new comets in the skies, like Comet SWAN. But how often do bright comets truly appear? 

Certainly, a bright comet is something amazing to behold. Of all the sky objects you can see without a telescope, my full Top-Five list includes: a total solar eclipse, a vivid aurora display, an exploding meteor, a brilliant comet, and maybe we should also include a bright rainbow as well. 

The rarest of these are bright comets and total solar eclipses, and it’s hard to figure which is the most infrequent. On the one hand, a total solar eclipse happens somewhere on Earth nearly every year. But its path of visibility is very restricted, so that to see one from your backyard is, on average, a once-every-360-year affair.

How Often Do Great Comets Appear?

A great comet, on the other hand, comes by every 15 to 20 years, on average. And when it does, it lasts for several nights or even a few months, and most of the world gets to see it.

We beat the odds and had the very unusual event of two bright comets only a year apart when comet Hyakutake hovered near the North Star in 1996, followed by much brighter Comet Hale-Bopp in 1997, which lingered for more than half a year.

But those spectacles happened almost a quarter century ago. Ancient history.

Headlines in March speculated that we were finally going to get a bright comet later this very spring. But many astronomers remained cautious, since comets are sadistic objects that tend to break our hearts.

Remember Comet Ison a few years ago, in 2013, the much-touted “comet of the century?” It was great for my daughter’s tour company, since 110 people signed up and came to Chile to see it. But, sure enough, as it came close, the Sun’s enormous gravity ripped it apart, and it visually fizzled. Just as Halleys Comet had done in 1986. And Comet Kohoutek a dozen years earlier, after making the cover of Time as, yes, you guessed it, that decade’s “comet of the century.”

Why Comets Are Hard to Predict

That’s because we always can calculate where a comet will be, but not how it will behave. And now, sure enough, Comet ATLAS has broken apart. It appears it will not put on any kind of show for us.

Still, have hope. We remain “overdue” for a “great comet” — one bright enough to be seen naked-eye even from cities.

Typically, the discovery is a surprise, since the typical brilliant comet has a 20,000 year orbit and thus is unknown to us prior to its discovery. We usually get a few months’ warning that it will pass close to us, and to the Sun.

Have a healthy skepticism when it comes to comets. Keep eating those health foods. And be patient.

Another Comet Arrives

So yes, ATLAS has fizzled, but a new comet has already arrived. Comet SWAN was spotted on April 11 and is currently bright enough to spot through a telescope or binoculars. 

Will Comet SWAN brighten or fizzle? Will it be the “next comet of the century”?  We wouldn’t count on it. 

Until then, let’s enjoy the many wonders of the night sky! From the beautiful stars and planets to magical auroras and eclipses, there’s an endless cosmos to explore.

About This Blog

Welcome to “This Week’s Amazing Sky,” the Almanac’s hub for everything stargazing and astronomy. Bob Berman, longtime and famous astronomer for The Old Farmer’s Almanac, will help bring alive the wonders of our universe. From the beautiful stars and planets to magical auroras and eclipses, he covers everything under the Sun (and Moon)! Bob, the world’s mostly widely read astronomer, also has a new weekly podcast, Astounding Universe