Of Comets and Pandemics
Updated: Jul 25
As half of the world’s population is in lockdown to slow the spread of deadly virus, a bright comet named ATLAS is about to visit us. Today, we know that the simultaneity of these two events is pure coincidence. However, before the work of Edmund Halley, people saw the appearance of a comet and a pandemic as dramatic displays of God’s anger with them.
Our ancestors had an intimate relationship with the night sky. Most likely, our nomadic ancestors used the seasonal changes of constellations to decide when winter and summer were on the way, and so when to migrate. We know farmers of the earliest civilizations used constellations to decide when to plant and harvest crops. It’s no exaggeration to say that the very lives of our ancestors depended on the clock-like motions of the Sun, Moon and constellations. The predictable motions of these celestial objects must have given our ancestors a great sense of awe and comfort.
Unfortunately, the clock-like regularity of the night sky was interrupted a few times every lifetime. Specifically, a comet would suddenly appear, steadily brighten, grow a long tail, and then fade away all over a few months. Comets reminded the ancient Greeks of stars with long, unbound, hair. In Greek, the word comet means “hairy star.” Comets weren’t predictable like the Sun, Moon, and constellations. Their unpredictability made them scary. Just about every culture around the world and throughout human history were scared of comets.
In his book “Comets”, Carl Sagan describes the view of religious authorities on comets. In 1455, Pope Callixtus III became so worried about the appearance of a bright comet during the crusades, he excommunicated it. Martin Luther (1483-1546) preached, “The heathen writes that the Comet may arise from natural causes; but God creates not one that does not foretoken a sure calamity.” In 1578, Lutheran bishop Celichius described comets as, “the thick smoke of human sins, rising every day, every hour, every moment, full of stench and horror before the face of God, and becoming gradually so thick as to form a comet, with curled and plaited tresses, which at last is kindled by the hot and fiery anger of the Supreme Heavenly Judge.”
Under these circumstances, it’s easy to see how people would see comets as foreshadowing disaster. For example, in late 1664 a spectacularly bright comet appeared in the sky over London. It stoked fear in the hearts of the people as to what kind of catastrophe was on the way. Shortly after its appearance, the bubonic plagued ripped through the city and killed one-quarter of the inhabitants in a mere 18 months. Then, in late 1665, yet another comet appeared over London, only to have a great fire destroy 13,000 homes in the city in just four days. For the citizens of London, it was easy to link comets to disasters.
During the Great Plague and Great Fire of London, Edmund Halley was a young boy and lived on the outskirts of the city. These events must have had a profound impact on him. Fortunately for Edmund, personal hygiene became a big hit with the people of London after the Great Plague, and as a result his father’s soap business became highly lucrative. Edmund’s father was able to support his son’s interest in astronomy by supplying him with telescopes and the best possible education, and Edmund took full advantage of these opportunities.
Edmund made many contributions to science, but he is most famous for his work on comets. Specifically,
Edmund came to suspect that comets orbit the Sun like planets, and the comets of 1531, 1607, and 1682
were not three different comets, but the same comet making three passes by the Earth. So, Edmund used Newton’s brand-new laws of physics to predict the return of the comet by the Earth. Decades after Edmund’s death, a German amateur astronomer found the comet at the location and time of Edmund’s prediction. Edmund explained away the fear of comets, and for the first time humankind could just enjoy their beauty.
The last naked eye comet to appear in our sky was over 10 years ago. Initial projections suggest comet ATLAS may be a spectacularly bright comet this spring. But as the famous comet astronomer David Levy said, “comets are like cats in that they have tails and they do what they want.” If ATLAS becomes a bright comet, it might be well worth your time to step outside and look for it. You might not have too many more chances to see a bright comet in your lifetime.
When and where should you look for the comet? You should start looking for comet ATLAS in the middle of May. As the figure shows, on the night of May 15 look toward the western horizon for the brightest object in the sky, Venus. Then, look to the right of Venus, and hopefully you will see a bright comet ATLAS.
Update May 2, 2020 (Comet SWAN)
I have some good news and some bad news in this update. First, the bad news. On its way toward the Sun, comet ATLAS broke apart. An image of ATLAS taken on April 23, 2020 with Hubble Space Telescope shows at least a dozen pieces. See the image below. The comet is fading. Unless something unexpected and spectacular happens, ATLAS won't be a naked eye comet later this month.
The good news is there is another comet making its way toward the Sun, comet SWAN, and it's already just barely visible to the naked eye in the southern hemisphere. Here in the northern hemisphere, you should look for comet SWAN around May 15 through May 31. You will need to get up early and look really low toward the eastern horizon about an hour and a half before sunrise. Here in Flagstaff, AZ, I will be out looking for comet SWAN as it crests above the horizon at about 4 a.m. I won't have long to view SWAN. As it gets closer to sunrise at 5:22 a.m., the sky will brighten and eventually wash out the comet. There are some predictions saying the comet will be easily visible to the naked eye. All of this assumes comet SWAN doesn't break apart like comet ATLAS. In the words of Harvard astronomer and father of modern comet science, Dr. Fred Whipple, "If you must bet, bet on a horse, not a comet."
Update July 18, 2020 (Comet NEOWISE)
So, comet SWAN crumbled just like comet ATLAS as it came close to the Sun. Neither comet was bright enough for naked-eye viewing.
Next, enter comet NEOWISE. It survived close passage by the Sun. NEOWISE is easily visible to the naked eye in the evening sky. You will want to go to a dark site with a good view of the northwestern horizon. It's best to start looking for comet NEOWISE about 90 minutes after sunset. The nights between July 18 and July 27 will be best as moonlight will be minimal. Face the northwest horizon. Find the Big Dipper, which appears to be hanging from its handle with its ladle extending down toward the horizon. Look below the ladle, and you should see comet NEOWISE. You won't have long to view the comet on any given night as it will dip below the horizon.
Below is an image of comet NEOWISE that I captured at the Kendrick Park Watchable Wildlife Trail in northern Arizona about 90 minutes after sunset on July 18, 2020.