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  • Writer's pictureLuke

Comet incoming!

Updated: Jan 29, 2023

We will be visited by a bright green comet this late January/early February! The comet’s official name is Comet C/2022 E3 ZTF but just shortining it to "Comet ZTF" has a better ring to it in my opinion(ZTF stands for Zwicky Transient Facility which is the observatory that first discovered the comet back in March 2022).

A time-lapse of Comet ZTF I took on 1/27/23

On the night/morning of Febuary 1st/2nd 2023 the Comet ZTF will make its closest approach making it brighter in the sky this whole week! It will be passing in the sky right between the Small Dipper (Ursa Minor) and The Big Dipper (Ursa Major).

Sky and Telescope magazine has a good image of where the comet will be in the sky for the next few months here:

A picture of Comet ZTF taken with my telescope on Friday 1/27/23

Comet ZTF should be fairly visible, a decent pair of binoculars or a decent telescope will probably offer the best views and you might be able to catch it with the unaided eye in a very dark place on the night of closest approach (Wednesday Feb 1st). It is hard to predict brightness of comets but about 5+ magnitude seems to be the current guess (about the brightness of Uranus, would barely be seen with dark skies and unaided eyes/require a small telescope or good binoculars to see).

Comet Neowise seen on an AstroTour in March 2020

The main factor working against the comet will be the moon. In the coming weeks the moon will be growing causing more and more natural light pollution and setting later and later. On the night of 2/1 the moon will be 83% full and setting at 5am making it highly likely to wash out the comet’s appearance to many viewers.

The word comet comes from Latin and means “long haired star” referring to the hair like tail, the most striking feature of a comet. The comet ZTF should appear with a faint cloud tail possibly with a green hue pointing away from the sun.

Comet 67P which was studied up close by the Rosetta mission

Comets are referred to as dirty snowballs as they are primarily made up of ice with some rock and dust mixed in. The tail of a comet always points away from the sun because the heat of the sun and the solar wind (a stream of charged particles the sun radiates) hits the comet with enough power to melt the ice and burn the dust. Watching the Comet ZTF in a telescope between the now and 2/19 the change in direction of the tail should be very apparent, flipping from pointing east to pointing north as the comet crosses the sky.

How a comet's tail changes as it orbits the sun

Up to the 1700s Saturn was seen as the limit of our solar system. Comets of course were known of prior to the 1700s as they are quite striking when they appear, however comets were seen as foretelling a large event. So instead of studying them when they appear many focused mainly on what upcoming event is being foreshadowed. Aristotle and many others thought comets were phenomenon which occur in the Earth's atmosphere. Edmund Halley famously predicted a comet he had seen in 1682 to return in 1758 this was the first insight into what comets really were. Halley’s comet meant that the solar system was much larger than previously thought as, the orbit Halley predicted had his comet traveling just outside of the orbit of Neptune (which wasn’t discovered until 1846) meaning the comet traveled over 3.7 times as far as Saturn’s orbit.

Halley's Comet during its pass through the inner Solar System in 1986

If you wish to see the Comet ZTF up close in one of my large telescopes and learn more about it I will be offering 2 special tours for the comet, one on Febuary 1st one in Boulder and one in Winter Park.

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