Is C/2020 F3 (NEOWISE) Considered a GREAT Comet?

The short answer? Probably not – based on historic comets that were significantly brighter.

With that said, it’s surely a candidate – and if C/2020 F3 (NEOWISE) does officially get designated that prestigious title of “Great Comet of 2020” then I’ll be happy to call it that.

What defines a “Great Comet?”

 A Great Comet in the most layman explanation is one that gets exceptionally bright – so bright that people can easily notice it in the sky despite not looking for them. 

It also helps that they’re widely remembered by non-astronomers because of all the attention they get and how much they inspire people to go see them. 

How bright are we talking? We usually mean comets that get in the negative magnitude territory (in astronomy the lower the magnitude the brighter the object), comparable to bright planets like Jupiter or Venus. Some, like the Greats of 1910 (NOT Halley) and 1965 were visible in the day!

Even comets that are as bright as zero magnitude stars or brighter like Vega and Arcturus can appear exceptional if they are visible high enough in the sky after dark.

That’s why Hale-Bopp ’97 was so widely remembered – at its brightest, the coma got to about mag. -1.5, two tails were easily visible, and it was in a position in the northern sky where you could see it long after dark. It also helped that it was bright enough to be easily observed from within light polluted cities, and naked eye visible from Earth for over a year!

It also appeared at the right time thanks to a newly widely available invention called the internet allowing people to share their pictures of Hale-Bopp ’97, helping gain more widespread attention that many Great Comets of the past didn’t get.

Why Would C/2020 (NEOWISE) Be Considered a “Great Comet” Candidate?

It made the headlines and gained a lot of attention, and rightfully so! It inspired countless people to go out and observe it. Not only did I repeatedly go out and observe it early in the morning from 7/6-7/12, but I went out to Joshua Tree National Park on 7/18 specifically to go see how this comet performed from a dark location. It meant a lot to yours truly that I convinced over 20 people to get up at 4am to join me in seeing it!

7-12-20 comet neowise3
A patron is silhouetted with my telescope. You can see the comet to the left of her head.

My colleagues were always going out and photographing it from various locations. My boss reported that at Mt. Wilson, he saw hundreds of people parked along the mountain roads, many of which were set up at a spot where the comet was obstructed.

It’s sad to say, but if our Observatory was open to the public during this time we would have had all of our public telescopes showing it throughout mid July (thanks a lot, Global Pandemic!).

7-10-20 comet neowise2
From Gavilan Hills, about 4:30 am on 7/10. San Gorgonio Peak is the distant mountain to the bottom roght.

At its brightest, it was easily visible to the naked eye from within the cities…. BUT…. you had to know exactly where to look!  I could see it with the naked eye from a moderately light polluted Gavilan Hills, CA sky from 7/6-7/10, but by 7/12, one had to use averted vision to catch it. When it emerged in the evening sky, it was practically invisible to the naked eye from light polluted locations despite being as bright as the stars of the Big Dipper. This is because a diffuse object doesn’t look as bright as a sharper point of light at book value – plus the combo of light pollution and haze makes it much harder to spot!

7-18-20 neowise landscape

When I saw it again on 7/18, this time from Cottonwood Campground in Joshua Tree National Park, even though it was still a magnitude +2.5 object, the 6° long tail was very obvious to the naked eye thanks to there being no light pollution or thick haze. I’ll never forget hearing all the nearby campers cheering when it emerged in the night sky after dark.

It Reminds of Other Past Comets Deemed “Great!” 

While surely not as bright or easy to spot as other past “greats,” C/2020 F3 has still displayed on a similar showing that other past “greats” have done:

Mrkos ’57 had a max brightness of about +1, and was a second magnitude comet in the morning and evening sky with at least a 5° long dust tail. It was naked eye visible for about two months.

Bennett ’70 peaked at magnitude 0 in late March and spotted an estimated 5-10° long tail. Throughout April that year, it dimmed from mag. 1 to mag. 5 while being an early morning target.

So then the question is to be asked: why would those two comets be deemed “Great” but NEOWISE 2020 not be?

Okay… Why Would we NOT call NEOWISE a Great Comet?!

It Never Got Exceptionally Bright!

Yes, the long dust tail, and the addition of the second ion tail has been very impressive, and fun to take pictures of.

I’ve seen various people and Twitter feeds already call NEOWISE a Great Comet, and I’ve even encountered one person who went as far as saying “It’s more impressive than Hale-Bopp!” I’m sorry, but that’s just not the case!

Even though NEOWISE has surely been impressive to astronomers and casual viewers alike, it has NOT been an exceptionally bright comet. The brightest it got was about the same magnitude as Saturn (+1), but  it was less than 15 degrees from the Sun, hence it was really tough to see unless you knew where to look. Hale-Bopp ’97 on the other hand – you had to be living under a rock to miss it at night in March-April that year.

During the period when it’s an evening target, while it gets progressively higher and stays in the sky longer after dark, it also gets progressively dimmer due while moving away from the Sun – which is very typical comet behavior.

Naked Eye Does NOT Automatically mean “Great!”

Yes, a Naked Eye level comet is rare. One that has a long visible tail is even rarer. But while a large comet with a visible tail that’s a magnitude 2-4 in the sky is surely a naked eye object, it’s one that you need to go out to a dark location to see it!

Otherwise, you need at least binoculars to catch it from cities, and even then it’s not as impressive as it could look. Many famous and infamous comets suffered from a disappointed public reaction because of light pollution, and sadly, there will be many more that miss out on NEOWISE because of this.

Casuals often come up to me and tell me they’ve spotted something they didn’t notice before – these are objects turning out to be either Venus, Jupiter, or anything brighter than zero magnitude because it’s simple: they’re really bright! If NEOWISE got as bright as the objects listed prior while in the same visible position in the sky, then yes, without question it would easily be designated the “Great Comet of 2020.”

If you Still Feel Like NEOWISE is a Great Comet, Then Who Am I to Say, “No!” 

With the age of light pollution making it much harder to see naked eye level comets, is it possible that many “Great Comets” of the past would not be considered as such anymore? Yes.

If you based C/2020 F3 (NEOWISE)’s brightness and visible tail after dark in mid July evenings from a location with no light pollution, then yes, it was noticeable even if you weren’t looking for it (the very definition of a Great Comet). Famous disappointments like 1974’s Kohoutek and Halley’s 1986 appearance would still be considered impressive, possibly even “Great” because they were still visible to the naked eye and sported long tails from dark locations.

If you based it on how much attention it got or how much non-astronomers will remember it, then there is no question that NEOWISE surely got a lot of that.

But the two famous disappointments mentioned prior are also notoriously infamous because… well.. they disappointed a lot of people!

There were also many Great Comets in the past that had almost little to no media attention outside the astronomy circles, at least not to the levels where casuals are informed, because they were either not promoted enough (West ’76 – not promoted due to Kohoutek ’74 backlash), the comets were best visible in the “wrong hemisphere” (McNaught ’07 & Lovejoy ’11 – best for Southern Hemisphere)  or they weren’t very bright for very long (Hyakutake ’96 – only spectacularly bright for a couple of nights). 

7-18-20 neowise 70mm

The point is, there is no official definition of a “Great Comet” except that a comet must be really really bright to be easily called one.

Whether NEOWISE officially gets crowned that title or not, one thing for certain is that it reignited the spark of interest in astronomy for many people! Just as Hale-Bopp ’97 inspired the nine year old me, NEOWISE 2020 has definitely done the job for kids and adults, and has put on a show that skywatchers and casuals alike have been itching for after so many years!

One awesome thing I have noticed is thanks to NEOWISE, there are more people getting interested in telescopes, and doing the right thing by asking people like us for helpful advice!

I am honored to have been able to document it, and take pictures to help inspire more people to check it out!

And because it gained a lot of attention, and because it’s the brightest comet visible for northern viewers in over 20 years, a lot of people outside the astronomy community will remember it – until the next GREAT comet appears and outshines it!

When that happens, it’ll be more like NEOWISE who?