Excitement surrounds comet C/2020 F3 (NEOWISE)

Purity and Pollution. Comet C/2020 F3 NEOWISE floats serenely among stars above clouds glowing brightly from light pollution. Photo by James Guilford.

Comet C/2020 F3 (NEOWISE) was, for us in North America, a predawn object requiring exceptional dedication for observing.  In the second week of July, the comet had moved enough in its orbit to become visible in the evening sky — from late twilight to about 11 p.m. Unfortunately, cloudy nights have been the rule lately so opportunities have been few.

On Wednesday night, July 15, the sky forecast was a bit shaky but it turned out the sky cleared enough to allow C/2020 F3 to be seen. I raced off to an observing site some 25 minutes away from home, popular with sunset watchers and, occasionally, comet spotters. Arriving at the site I found the place mobbed, the parking lot nearly full, by scores of would-be comet viewers. Unfortunately, the comet was pretty much at the low end of naked-eye visibility. Light pollution reduced contrast between comet and background sky to make the object nearly invisible — binoculars were needed. It’s likely most of those in attendance never saw the comet.

Entitled “Purity and Pollution,” this picture (a single exposure of 8 seconds) shows a pristine wonder of the night sky floating serenely amongst the stars, clouds glowing brightly below illuminated by artificial light pollution. If we were only more careful with our artificial light, we’d save plentiful energy (and money) and gain back our starry skies as a bonus!

C/2020 F3 (NEOWISE) will be gracing our night skies for the next week or so and I hope to have more than one opportunity to record the event before it is gone. The next apparition of this comet is expected in about 6,800 years.

A visitor from outer space

Seen at 5:00 in the morning, July 9, 2020, C/2020 F3 rises over calm Lake Erie waters and predawn colors. Photo by James Guilford.

The talk amongst stargazers this summer has been the apparition of C/2020 F3 NEOWISE in Northern Hemisphere skies. Previously one comet had caused excitement over its potential showing but it broke up as it approached the Sun. Another fizzled and faded from view. But C/2020 F3 survived its July 3 close approach to the sun (perihelion) and emerged bigger and brighter than expected.

The comet’s brightness is due to its large nucleus — the head of the comet — which is the source of frozen gas and dust that produces the visible tail or coma. “From its infrared signature, we can tell that [the nucleus] is about 5 kilometers across,” said Joseph Masiero, NEOWISE deputy principal investigator at NASA’s Jet Propulsion Laboratory.

C/2020 F3 was discovered in infrared images captured by NASA’s NEOWISE spacecraft in March 2020. The object was assigned the unromantic designation of C/2020 F3 with the spacecraft’s name as discoverer.

Comet C/2020 F3 with normal exposure (top), then brightened in processing to bring out fuller extent of its dust trail (lower image). Photo by James Guilford.

Falling in from the outer solar system, then diving perilously close to the Sun gave our comet a boost in speed and increased its orbital period from about 4,500 years to about 6,800 years — a long time to wait for its return.

Until recently C/2020 F3 put in its appearances only in the predawn hours, rising a little after 3:30 AM and fading into the brightening sky a bit past 5:00 AM. It was also rising to only about 10º above the horizon placing it, much of the time, in the realm of morning clouds, mists, haze, and general murk.

But it’s not over.

While at the time of this writing C/2020 F3 continues to be viewable in the wee hours before dawn in the northeastern sky, sinking lower with each morning, it is now also showing in the post-sunset twilight. It’s still only becoming visible around 14º to 10º above the north-northwestern horizon as it sinks toward the horizon following the Sun. The comet sets around 12:30 AM.

July’s evening sky offers more convenient viewing hours for C/2020 F3. Credit: SkySafari

Evenings, for the next couple of weeks and possibly into August, go comet hunting! Depending upon whether the sky is clear of obstructions, clouds, and haze, skywatchers may be able to see the comet with unaided eye. Good binoculars will help in finding it and will give seekers a better view. The comet will be very low to the horizon so an elevated location will aid in viewing. Use binoculars to look west and then past northwest in the deepening twilight, scanning slowly and just above the horizon. The comet will appear as a vertical streak with a bright dot at the lower end, as in the picture at the top of this page. It may not be spectacular but how many comets does one see in their lifetime?

Our outbound visitor from outer space makes its closest pass by Earth on July 23 when it will be 103.7 million kilometers — about 64 million miles — away returning in roughly 7,000 years.

Can you see the comet named SWAN? Ummmmm…..

Can you see the comet named SWAN? The answer is, with luck, maybe. If we wish to see Comet SWAN, we’ll want some clear nights coming in the next week or so. Here’s a chart with hand-drawn positions of C/2020 F8 (SWAN) over the next month. June 2 would be our best opportunity as the comet will be highest above the horizon and near the star Capella, which will help in finding it. Getting the timing right will be challenging, between twilight fading enough for the faint object to be seen and spotting it before the comet sets! You’ll still need good binoculars to see this one and a clear view to the northwestern horizon. Place your order now for clear skies to be delivered the night of June 2 … DO IT NOW! Supplies are limited.

Chart of Comet SWAN's path May 22 to June 22
Comet C/2020 F8 (SWAN) will make a low arc across the northwestern horizon over the coming month. Here’s a hand-drawn plot. Credit: SkySafari/J. Guilford

Comet SWAN has been a Southern Hemisphere object until just recently. I’ve heard some people here, up north, have caught glimpses of the comet already though it’s so low to the horizon that, even with clear skies, by the time the sky gets dark in the northwest, the comet is setting! And as the days and weeks pass, the progression of the starry background takes everything closer to the horizon — or you could think of the horizon rising, when looking at a chart. Add to that the fact that days are getting longer, sunset and twilight later, the comet lower… ugh! It seems everything’s a race! By mid-June Comet SWAN will be lost in bright twilight.

Comet C/2020 F8 (SWAN) was officially discovered March 25 of this year. It will make its closest approach to the Sun (perihelion) on May 27 when it will be 64 million kilometers from our star. Officially classified C/2020 F8 (SWAN) the new comet was first spotted by Australian amateur astronomer Michael Mattiazzo on April 11 using data from the Solar Wind ANisotropies (SWAN) instrument aboard the NASA/ESA Solar and Heliospheric Observatory (SOHO) recorded on March 25.

If you spot SWAN, please let us know! Good luck!


Comets, being temperamental beasts, don’t always act as we’d expect or hope. Most of the time comets gain brightness as they draw nearer the sun; Comet SWAN has been dimming! I’d seen earlier mentions but this Sky & Telescope article just came out today… HUMBUG!

Recalling an outburst: Comet 17P/Holmes

Photo: Comet 17P/Holmes by James Guilford
Comet Redux. Reprocessing old images shot through the Stephens Observatory telescope shows Comet 17P/Holmes as it appeared October 28, 2007. The two dots are bright stars shining through the comet’s coma. Photo by James Guilford.

Back in 2007 astronomers were excited by a comet known as 17P/Holmes. What was so exciting was that the seemingly ordinary visitor from distant parts of the Solar System suddenly put on a great show. In October, the usually dim 17P/Holmes changed from an unremarkable telescopic object to become visible to the unaided eye, appearing as a yellow “star” in constellation Perseus. It was briefly the largest object in the Solar System. The outburst was believed to be similar to one that took place in 1892 making it visible to amateur astronomer Edwin Holmes, credited with its discovery on November 6 of that year. The reason for the sudden brightening or outbursts remains unknown.

I used my little Canon Rebel XT digital camera attached to the vintage Cooley Telescope at Stephens and attempted to capture images of the comet. The effort and the camera were pretty primitive compared with what we can do now but I got some images and they were the best I could manage at the time. Comet 17P/Holmes faded from visibility over the next several weeks. The somewhat odd appearance of the comet — no classic head and tail — is the result of our perspective: looking straight down its tail instead of from the side.

Recently I viewed a television show about comets and the strange behavior of 17P/Holmes was discussed. That program reminded me of the 2007 apparition and to look at my old images. There wasn’t much image data to work with but I reprocessed what I have and produced a new image a bit better than my first try; that image, shot through our old telescope, appears above.

The “P” in the comet’s designation stands for periodic, meaning after a period of time 17P will return to loop, once again, around Sun. In March 2014 (a seven-year period) the loop was made without an outburst. The next close approach to our Sun, perihelion, will take place on February 19, 2021. Will we be treated to another show?

— James Guilford

Let’s look at Jupiter April 22

Illustration: Jupiter and His Moons as They will appear April 22, 2017, 10:00 PM EDT
Simulation: Jupiter and His Moons as They will appear April 22, 2017, 10:00 PM EDT

FINAL UPDATE: In all, 18 people and one dog took a chance on the changeable skies and paid the observatory a visit. Cloud cover ebbed and flowed, changing Jupiter’s appearance through the telescope. Interestingly, some of the better views of the planet actually occurred when thin clouds dimmed the brilliant planet cutting the glare. Viewers could make out the gas giant’s two major temperate cloud belts and sometimes one or two more! The four Galilean Moons were visible nearly all of the time. Owing to generally poor viewing conditions, the evening was limited to Jupiter only – dimmer objects were not available. The April 22 program will be repeated in May, given clear skies. By the way, before the dog came, a cat arrived with one of our visitors but refused to come inside, so kitty didn’t count!

UPDATE: Saturday, 9:00 PM: Opened when we could see Jupiter through thin clouds but expect the sky will cloud over again before clearing in the wee hours. Check out Twitter feed to the right for updates and closings…

UPDATE, Saturday, 4:00 PM: Forecasts call for partly- to mostly-cloudy conditions tonight. A final go/no-go decision on opening will be made later but, if we do open, we DO NOT expect to be able to see dimmer objects such as star clusters or the comet listed below. More later….

Stephens Memorial Observatory of Hiram College will be open for public observing Saturday, April 22, from 9:00 to 11:00 PM. This will be the first scheduled Open Night of the 2017 season. The “star” of the night will be planet Jupiter, brilliant in our southeast sky. We will also seek out the M3 star cluster and, later, the Hercules Cluster and (with some luck) Comet C/2015 V2. Other objects of interest may also be viewed. Of course, all of the night’s observing depends upon clear skies and those have been in short supply this spring!

Cloudy skies at the starting time cancel the event and, in that case, the observatory will not open. No reservations are required and there is no admission fee for observatory public nights.

The Observatory is located on Wakefield Road (Rt. 82) less than a quarter of a mile west of Route 700 in Hiram. There is no parking at the Observatory. Visitors may park on permissible side streets near the Post Office, a short distance east of the observatory.