How to see Comet Leonard, aka the 'Christmas Comet', from New Zealand

Kiwis hoping to get a good look at the year's best comet will want to get out of the city, experts say.

Comet Leonard - nicknamed the 'Christmas Comet' for obvious reasons - will be in the skies over the southern hemisphere over the next few days, making its first visit to our part of the solar system since the last ice age. 

Leonard was first spotted on January 3 by University of Arizona astronomer Greg Leonard at Mount Lemmon Observatory, in the state's southwest. Its 80,000-year orbit takes it 550 billion kilometres away from the sun - more than 120 times further away than the most distant planet, Neptune. 

It first became visible to the naked eye around December 5, and has since grown a tail and twice rapidly increased in brightness, as the sun heats it up. 

Leonard swung extremely close to Venus at the weekend, coming within 4 million kilometres. 

Simulations on Stellarium suggest Leonard, also known as C/2021 A1, will be visible to New Zealanders in the lower half of the sky looking to the west - just to the left of Saturn and Jupiter, and above Venus. 

"At the moment it's basically after sunset out in the west," Stardome educator Josh Aoraki told Newshub. "You'll see there's three bright planets out that way - you've got Venus, which is the brightest, so that's a really good guide for where you're going to see the comet. It's basically above Venus. 

"So once the sun sets in the west, you're going to see that really bright-looking 'star' - the planet Venus. It's basically directly above that and it's slowly moving higher and higher every night."

Comet Leonard.
Comet Leonard. Photo credit: Adam Block / Steward Observatory / University of Arizona

On Friday night there will be a window of about an hour-and-a-half between sundown and when the comet falls below the horizon - you can blame the Earth's rotation for that. Over the next few days Leonard will appear higher in the sky, but its visibility will be unpredictable - it could easily fade from its current brightness. 

Its tail could be seen in a photo taken from Moa Pt in Wellington on Tuesday night by Matthew Shirley, who told Newshub it wasn't able to be seen with the naked eye.

Comet Leonard, as seen from Wellington.
Comet Leonard, as seen from Wellington. Photo credit: Matthew Shirley

Telescopes or maybe binoculars will be a must from urban areas.

"It will be very, very difficult to see in the city because of light pollution. It's not overly bright - it's not Halley's Comet or anything," said Aoraki. When Halley's Comet last passed Earth in the mid-1980s, it was easily visible to the naked eye. 

"If someone wanted to see it without a telescope you'd need to probably leave the city, get out to the countryside, somewhere where it's really dark," said Aoraki. 

Where Comet Leonard will appear, as viewed on Stellarium from west Auckland.
Where Comet Leonard will appear, as viewed on Stellarium from west Auckland. Photo credit: Stellarium

Its closest approach to the sun will take place on January 3, but it's not known if it'll last that long. The gravity of the sun is expected to speed Leonard up, and if it survives the intense heat it'll likely exit the solar system for good - meaning this will probably be the only chance humanity ever gets to see it. 

"It's speeding along at escape velocity, 44 miles per second," discoverer Leonard said (that's about 70km per second - fast enough to travel the length of New Zealand in 22 seconds). 

"After its slingshot around the sun, it will be ejected from our solar system, and it may stumble into another star system millions of years from now."

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