Don't Miss the Spectacular Sight of the Green Comet

Jan 25, 2023

Sungrazer

Stargazers around the world are preparing for a once-in-a-lifetime opportunity to see a greenish-colored comet with their own eyes. The C/2020 E3 (ZTF) comet is a "sungrazer." It passes exceptionally close to the sun during its orbit, which heats up the comet's surface, causing it to release gas and dust, creating a spectacular tail visible from Earth.

The comet is set to make its closest approach to Earth on February 2, making it the perfect time for stargazers to catch a glimpse. The comet is then expected to be only about 26 million miles from Earth. When talking about space, words like close are used on a different scale than in our daily use. For instance, in this case, our closest distance to the comet is still more than a hundred times the distance between the Earth and the moon.

When, where, and how to see the comet

The best time to see the comet is during the predawn hours, just before sunrise. Look towards the northeastern sky; the comet will be visible to the naked eye as a bright, greenish-white object. Binoculars or telescopes will enhance the view and reveal the comet's tail.

A previous comet, ISON, shows off its tail in this three-minute exposure taken in 2013. (Photo: NASA)

Astronomers are practical in naming comets, but looking at some of their names, makes me wonder what they would call their pets. I guess Luna would be a popular one for astronomers' pets. Let's look at this comet, known as C/2022 E3 (ZTF). The "C" indicates this is a non-periodic comet with an orbital period of more than 200 years. Next, you get 2022 in its name; that is easy; it stands for the year of discovery. The E further defines the date as the fifth two-week period of the year. But two other comets were already discovered in 2022 E, hence the name E3.

And the ZTF? That stands for the Zwicky Transient Facility, an automated survey of the sky that discovered the comet using the 48-inch Oschin Telescope at Palomar Observatory in California, abbreviated as ZTF. And bear with me, one more naming detail: the International Astronomical Union has not yet approved the little green one's charming name, hence the parentheses.

It’s not another Hale-Bopp sight

I expect the sight of the green comet to be breathtaking, although it won't come close to the spectacular view of the comet Hale-Bopp. I remember admiring it in the springtime of 1997 while hiking with friends for several days in the Cotswolds. There, far away from the light pollution of the big cities, it was clearly visible and brighter than any star in the sky except Sirius. Even while hiking in the afternoon, the comet was already visible during the last light of the day.

For scientists, the arrival of the comet is an exciting opportunity to study it. The comet is a dirty snowball, around 5 kilometers (3.1 miles) in diameter, made mostly of water ice and little pieces of rock and dust. The ice sublimates (turns into a gas) as a comet warms up and approaches the sun, releasing water vapor and hurling rock and dust particles into space. Like the comet, these little pieces of rock and dust continue to orbit around the sun. We would experience a meteor shower if the Earth passed through this debris trail.

How it gets its green color

This comet also contains carbon dioxide and carbon monoxide, which are rare in comets. It gets its green color because its diatomic carbon (a molecule consisting of two carbon atoms) absorbs ultraviolet radiation from the sun, which results in the emission of green light.

As comets are made mostly of ice and dust, they are considered some of the oldest objects in the solar system, dating back to its formation around 4.6 billion years ago. So studying the comet may reveal valuable information about the building blocks of the solar system and the conditions that existed during its formation.

Don't miss your chance to see comet C/2022 E3 (ZTF) because its orbital period is about 50,000 years. That means it will not be back until around the year 52,000. Considering the Doomsday Clock's scary approach of just 90 seconds to midnight, chances are that there won't be anyone humans around to see it then.

So don't miss your last opportunity to join the last humans to see the green comet; it's a sobering and exciting thought in challenging times for our species.