During my lifetime, comets have largely not lived up to the hype. Oh, they're cool, no doubt about it, but compared to accounts of the double-header of "daylight comets" that occurred in 1910 -- the unnamed "Great Comet" that appeared in January, and Halley's Comet in April -- the ones I've seen have been faint, visible to the unaided eye as a vague streak, showing their unearthly beauty only through binoculars or telescopes. The first comet I remember anticipating, Kohoutek in 1973, fizzled miserably, and the claims that it would be the "Comet of the Century" fell far short of the mark. Even Halley's reappearance in 1986 was a bit of an anticlimax, with a display that was nowhere near as spectacular as it had been in 1910.
But this time we may just have a winner.
Discovered this past December by the automated search program with the rather terrifying name "Asteroid Terrestrial-impact Last Alert System," Comet C/2019-Y4 (ATLAS) is already brightening rapidly, and has increased by four magnitudes in only three months. (It's currently at a magnitude of +15, well below the threshold for unaided-eye visibility.) If it continues on its current trajectory brightness-wise, by mid-May it could be at a magnitude of -8 -- four magnitudes brighter than Venus.
If that happens, it could actually be the best comet of the past hundred years.
Still, it's wise to remember the words of Canadian astronomer David Levy, co-discoverer of Comet Shoemaker-Levy in 1993, which made a spectacular collision with the planet Jupiter the following year. "Comets are like cats," Levy said. "They have tails and they do whatever they want."
So we really don't know for sure what it's going to do. Writing for the website Astronomy, Alister Ling says, "The big unknown: Is Y4 ATLAS a lightly powdered rubble pile that produces a meager tail that dissolves into nothingness? Or does luck strike us with a dust-choked snowball whose tail forms the magnificent sword we see in paintings of old? A touch of aurora or noctilucent clouds would really top off the light show."
One bit of good news for those of you who, like me, live in the Northern Hemisphere; if ATLAS puts on a grand performance, we've got front-row seats. The path of the comet against the backdrop of stars makes a swoop through the northern sky, starting near the Big Dipper, peaking in brightness in May as it passes the through the constellation of Perseus, finally disappearing from sight in June near Betelgeuse in Orion.
[Image courtesy of Alison Klesman (via TheSkyX)]
Ling waxes rhapsodic over what we may be in for:
The week of May 25 to 31 is the week when we take the iconic pictures of Y4 and forge our memories of a lifetime. ATLAS is literally diving past the Sun, brightening a magnitude per day. The top half of the tail remains above the horizon all night, drawing our view downward. As minutes flow by, the tail brightens, overcoming the rising oranges and yellows of dawn until it reaches the brilliant head of the comet, lifting off the horizon... If the sky is a dark transparent blue and ATLAS exceeds our expectations, we might snag the elusive trophy of a historical daylight comet.I know better than to get my hopes up too high; comets' catlike behavior has caught me too often before. But even if it's not the brightest object in the night sky, it should give us some fine opportunities for viewing, and even more for aficionados of astrophotography.
Whatever it does, it's nice to have something positive to look forward to. So keep your eye on the skies, and hope for a light show that will be something to remember.
Any guesses as to what was the deadliest natural disaster in United States history?
I'd speculate that if a poll was taken on the street, the odds-on favorites would be Hurricane Katrina, Hurricane Camille, and the Great San Francisco Earthquake. None of these are correct, though -- the answer is the 1900 Galveston hurricane, that killed an estimated nine thousand people and basically wiped the city of Galveston off the map. (Galveston was on its way to becoming the busiest and fastest-growing city in Texas; the hurricane was instrumental in switching this hub to Houston, a move that was never undone.)
In the wonderful book Isaac's Storm, we read about Galveston Weather Bureau director Isaac Cline, who tried unsuccessfully to warn people about the approaching hurricane -- a failure which led to a massive overhaul of how weather information was distributed around the United States, and also spurred an effort toward more accurate forecasting. But author Erik Larson doesn't make this simply about meteorology; it's a story about people, and brings into sharp focus how personalities can play a huge role in determining the outcome of natural events.
It's a gripping read, about a catastrophe that remarkably few people know about. If you have any interest in weather, climate, or history, read Isaac's Storm -- you won't be able to put it down.
[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]