Hoping that a comet will come our way

Pricked into the border of the 230-foot-long Bayeaux Tapestry, right before the coronation of the English King Harold and above the upturned heads and pointing arms of his retainers, is the Latin inscription “Isti Mirant Stella” (“These men wonder at the star”) and the unmistakable image of a blazing comet.

The appearance of Halley’s Comet in 1066 coincided with the Norman invasion of England, though chronologically it took place a few months after what from William the Conqueror’s perspective was Harold’s “usurpation.”   

As portents go, save only a total solar eclipse,  the appearance of a great comet is about as good a celestial event as one could wish. Now, in this plague year of 2020, we are about to receive a visitation from a comet with the potential to be spectacular.

Comet C/2019 Y4 was first detected in the last days of the old year by the Mauna Loa, Hawaii-based Asteroid Terrestrial-impact Last Alert System (ATLAS), and is now visible with the aid of more modest telescopes.

Sometime in late April, when there is a sliver of new moon in the sky, astronomers predict that what is being called Comet ATLAS will be a naked-eye object, and could be brighter than Venus as it makes its closest approach to the sun in late May 2020.

I have seen four comets in my 52 years on this Earth. When I was a very little boy, in 1973, my parents took me out one winter night to the airport in the hills above Worcester, Mass., to see Comet Kahoutek (C/1973 E1), making its first approach in 150,000 years.  I do not recall being impressed, and indeed Kahoutek failed to deliver, partially breaking up as it swept toward the sun.

When I was in high school, Halley’s Comet made an underwhelming pass after 86 years, but the next two comets were greater by orders of magnitude. Comet Hyakutake (C/1996 B2) came so close to the Earth that observers could easily track its movement — a Moon’s breadth in half an hour’s time.

It blazed with a long tail but only briefly, growing fainter between late March and May, and its memory has been eclipsed by Comet Hale-Bopp (C/1995 01), which arrived later in 1996 and which I saw in both hemispheres.  The clear desert skies of Namibia made a brilliant backdrop for a comet outgassing in a broad V above the Damaraland escarpment.

As author David H. Levy memorably puts it; “Comets are like cats: they have tails, and they do precisely what they want.”

Whether Comet ATLAS is a bang or a bust depends on a number of variables. It has an estimated orbital period of  about 5,000 years.  Its nuclei have started to develop an aqua-blue tail that, because of its orbital trajectory, could achieve an impressive, reflective length at its nearest approach.

The size and composition of the comet itself is still unclear, so it is hard to predict how bright ATLAS will get or whether it will break up under the pull of the Sun’s gravity.

Those inclined to read meaning into coincidence may note that the emergence of the novel coronavirus and its exponentially growing global infection curve are closely aligned with the arrival of Comet ATLAS. Those of us who desperately need something marvelous and wonderful to brighten our lives at this time live in hope that ATLAS will deliver.

Tim Abbott is program director of Housatonic Valley Association’s Litchfield Hills Greenprint. His blog is at www.greensleeves.typepad.com.