bright visitors

say hello to Earth's latest luminous passerby, comet Tsuchinshan–ATLAS

Dear word explorer,

As someone who constantly ponders humanity and Earth’s place in this mind-boggling cosmos, I’m always fascinated by the regular and irregular visitors who whizz by our planet.

In the past I’ve discussed the comet 12P/Pons-Brooks (which has a 71-year orbit) and Swift-Tuttle (with a 133-year orbit), but at the moment we’re getting great views of comet Tsuchinshan–ATLAS (officially, it’s classified C/2023 A3). You can see it with binoculars if you’re in the Southern Hemisphere, but it’s growing ever brighter for those of us in the Northern Hemisphere.

Its name comes from the two observatories that independently spotted it within a month of each other back in early 2023 — the Purple Mountain Observatory, also known as Zijinshan Astronomical Observatory east of Nanjing, China and the Sutherland Observatory in South Africa, which is part of the Asteroid Terrestrial-impact Last Alert System (ATLAS) developed by the University of Hawai’i and funded by NASA.

ATLAS has four telescopes scanning the heavens for near-Earth objects as an early-warning system for possible collisions with our planet. The first one, part of the Haleakalā complex on Maui, Hawai’i, came online in 2015 and has since been joined by a telescope on Mauna Loa, also on Maui, the Sutherland Observatory, and El Sauce Observatory in Rio Hurtado, Chile. You can watch the observations from any of the four ATLAS telescopes in real-time if they are in operation.

I suspect that many people are profoundly de-sensitised to the wonders that technology offers us today. If you are conditioned to scroll past so many micro-clips of disasters and mundanities every hour it’s hard to slow down and marvel at the rapid and incredible advances of modern science.¹

I was just able to remote-view a section of the heavens from my home in south Galway, Ireland thanks to information broadcast via broadband from an observatory in Hawai’i! Consider me awe-struck!

The Haleakalā High Altitude Observatory by Jad Limcaco on Unsplash

A good evening for viewings of Tsuchinshan–ATLAS will be Friday, 27th of September, when it reaches its perihelion — its closest point to the sun during its estimated 80,000-year-long orbit. If it doesn’t break apart from the sun’s heat², on the 12th of October it will have its near-Earth experience, when it may be visible with the naked eye. Afterwards, it will diminish as a presence in our skies over several weeks. This bright visitor might even be designated a ‘Great Comet’ due to its exceptional visual impact, down the lines of Halley's Comet.

But let’s consider that time frame: based on current information, Homo Sapiens emerged about 315,000 years ago. A hop, skip and a jump later in evolutionary terms — 74,000 years ago, approx. — the Toba supervolanic eruption occurred at Lake Toba in Sumatra, Indonesia. It is thought to have profoundly impacted life on Earth, and reduced the numbers of the emerging human species.

Although humans only invented writing about 5,000 years ago, our ancestors were marking celestial movements on monuments, caves and objects for at least 30,000 years.

For instance, the Loughcrew megalithic passage tomb in Ireland, which is approximately 5,000 years old³, is aligned to the equinoxes. For a three-day period last weekend, the sun rose and shone into its highly decorated inner chamber, and illuminated its keystone. Just as it has done for millennia thanks to the engineering skills of our star-loving stonemason ancestors.

Drawing of the keystone at Loughcrew, by Dutch artist, George Victor Du Noyer, 1866

And when we think about passing comets or asteroids we should always appreciate our giant ally in the solar system: Jupiter, the fifth planet away from the sun. Our gas giant neighbour is enormous, roughly ten times the size of Earth, and with a mass that is 2.5 times that of all the other planets in the Solar System combined! Thus, its gravitational pull is mighty. It is sometimes referred to as ‘the vacuum cleaner of the solar system’ because it sucks in so many passing objects, or changes their course so they head into the sun (or, sometimes, towards Earth!).

If it bats an occasional object in our direction, we should forgive it and consider that Jupiter suffers approximately 2,000 foreign body impacts in our solar year. Thanks for taking the hits, buddy!

I’m bringing this up because comet Tsuchinshan–ATLAS is thought to originate in the Oort Cloud, which is composed of billions of comets rotating on the outskirts of the solar system, trillions of kilometres from the sun (for instance Pluto, on average, is about 6 billion kilometres out).

Tsuchinshan–ATLAS has been quietly motoring through the solar system⁴, bypassing the influence of Pluto, Neptune, Uranus, Saturn, Jupiter, Ceres, Mars, Earth, Venus and Mercury, pulled irresistibly by our sun. As part of its celestial tour it will swing by for a gander at our planet as it continues on its long orbit back to the Oort Cloud (if it does not get hoovered up during its subsequent journey).

What tales it will have to tell when it returns to its teeming siblings!

Go out and give this determined voyager a wave!

‘Comet over Alkmaar’, Lambert Doomer, 1681

1. I’m not harshing the buzz of people who love their TikTok videos or Reels. Those blip-clips can be a temporary source of happy escape when life is less than kind, but the issue I’m pointing out is when it becomes a numbing habit so that all input is emotionally flattened and none of it matters.

2. I’m rooting for it, since astronomers predicted it was inevitable that it would break up some time ago, and it has defied expectations.

3. Usually attributed to Sumer (present-day Iraq), where a Mesopotamian cuneiform script formalised around 3200 BC, although it was coming into being as a counting system for several thousand years before that.

4. At 290,664 km per hour, or 80.74 km per second relative to Earth!