Sat. Mar 2nd, 2024
Comet NEOWISE (C/2020 F3)

Our night sky seems to be an element of perfection.

While the stars rise and set, and the sun, moon, and planets appear to move against the starry background, few changes are evident.

However, that stillness is occasionally interrupted by ghostly intruders: comets!

And right now, our eyes are fixed on Comet NEOWISE!

So what is a comet?

A comet is a remnant of the formation of the solar system.

Typically no more than five to 10 kilometers in diameter, these “dirty snowballs” are composed primarily of ice and rock material.

As they approach the inner part of the solar system, the sun’s heat begins to warm the core and the materials sublimate (go from the frozen state directly to gas without passing through a liquid phase).

In this image, the nucleus of comet 67P/Chuyumov-Gerasimenko can be seen sublimating into jets of gas that release icy, dusty material far from the nucleus itself.

kiteComet 67P/Churyumov-Gerasimenko. Photo: European Space Agency

When we look at a comet from Earth, we do not see the comet’s nucleus, but rather the layer of material released by the comet’s nucleus: the coma. A coma is, in essence, the localized atmosphere of the comet’s nucleus.

kitePhoto: Bill Gardner — Pictor Observatory

Although the nuclei of comets are quite small, the material left behind after their journey can extend more than 100 million kilometers.

Sunlight, reflected from this long chain of dust and gas, is visible as the comet’s tail.

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In detailed photographs (like this one taken by Killarney Provincial Park’s resident astronomer Bill Gardner), two different tails can be seen. The brightest is the “dust tail” composed (unsurprisingly) largely of dust and gas.

It generally points away from the sun, but is also somewhat affected by the comet’s speed and direction of travel, and often appears somewhat curved.

The ion tail tends to be blue in color and always points directly away from the sun due to the effect of the solar wind.

What happens to a comet after it passes?

Most comets are in long orbits around the Sun that can take them far beyond the dwarf planet Pluto. Some of these visitors may be on a one-time pass through our neck of the woods and never be seen again.

It is estimated that Comet NEOWISE (C/2020 F3) will move so far from the sun that its next pass will not be until the 89th century.

Watch it now or you’ll have a long wait ahead!

Interestingly, the dust left behind after the comet’s travels remains in orbit around the sun, following the same path that the comet followed. If the Earth encounters this material, it will burn up in our atmosphere (and we call that a meteorite).

comet in the skyPhoto: Bill Gardner — Pictor Observatory

Now you have the origin of the other element we see changing in our night sky: meteor showers. In fact, comets are the source of most of the meteor showers that we are privileged to see grace the starry night sky, and which are best enjoyed from our provincial parks.

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How to find comet NEOWISE (C/2020 F3)

There are many good sources and guides to help you find the comet. Here are some found online:

Observing the comet

While you can easily see the comet with the naked eye in dark skies, binoculars are probably your best optical tool for enjoying some of the comet’s details.