Farewell, 3I/ATLAS. I've been observing the interstellar comet for months. Here's what I learned

If you're wondering why it's suddenly gone so quiet about Interstellar comet 3I/ATAS when it's been front page astronomy news for months, it's because it's vanished.

Not literally - it's still very much there, out in the black - but it's now so faint and so far away that it's vanished as far as most amateur astronomers are concerned.

Right now, after moving through Leo as the year began, the comet is located in the constellation of Cancer, just a hand’s width to the west of the famous Beehive Cluster, M44.

From mid-northern latitudes it rises in the late night/early morning hours and reaches a reasonable altitudes before dawn.

It is shining – if that’s the right word – at around 14^th magnitude, so only cannon-sized telescopes are able to see and photograph it clearly.

At the start of February 2026, 3I/ATLAS will drift across Cancer’s border and move into Gemini, by which time it will beyond the reach of all but the very largest telescopes.

So, to all intents and purposes, at least as far as amateurs are concerned, its brief visit is over.

Which means that, seven months after Comet 3I/ATLAS was discovered on 1July 2025 by the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescope located in Río Hurtado, Chile, it's time for this writer and my comet 3I/ATLAS blog to wave a final goodbye to the comet that was born a long time ago, around another star far, far away.

A journey through interstellar space

Let’s start our farewell by looking back at Comet 3I’s past – at least, as far back into its past as the immediate aftermath of its discovery.

You'll remember that, encouraged by 'speculation' from certain individuals on X and YouTube that 3I was an alien spacecraft, perhaps even the advance scout ship of an extraterrestrial invasion fleet.

Of course, it wasn't; even the very earliest observations proved that.

But that didn’t stop social media clogging up like a blocked drain with a fatberg of reports of secret NASA detections of flashing lights, spooky radio broadcasts, unknown metals, engine exhaust plumes and sudden course changes.

All totally ridiculous. The object approaching from the depths of space was just a chunk of dirty, dusty, ancient ice - a comet.

For more on this, read a real astronomer's report on why comet 3I/ATLAS isn't aliens, and the rather sobering – but predictable – results of a study on 3I/ATLAS from proper SETI scientists.

But it was a special comet. It was a comet from another star, a distant sun burning somewhere out in the Milky Way, and as it whooshed through our solar system, skidding around the Sun like a stolen car in a Fast and The Furious film, astronomers scrambled to observe 3I ATLAS each and every way they could.

The largest telescopes in the world gazed it through the open doors of their mountaintop observatory domes, as up in space the Hubble and James Webb telescopes slewed towards it to study it with their unblinking electronic eyes too.

The comet was even imaged by space probes orbiting Mars, as it passed the Red Planet, making 3I ATLAS one of the most observed comets in history.

And all the astronomers working with those instruments, wherever they were, learned a lot about its size, its structure, composition and behaviour, delighted almost beyond words to have the opportunity to study something that was so rare, so alien, from so very far away.

3I/ATLAS has left the building

The comet is now outbound, well beyond Earth's orbit and heading toward the outer Solar system. It passed perihelion (its closest point to the Sun) in late October 2025, when it was about 1.4 AU away, or just inside Mars' orbit.

It is now roughly 2–3 AU from the Sun, and getting further away every day.

In March 2026 it will pass relatively close to Jupiter (~0.36 AU), an encounter which may slightly alter its path.

At the start of July, the comet will cross Saturn’s orbit, It will cross Uranus’ orbit in April 2027 and Neptune’s orbit a year later.

After that it will finally exit our Solar System, heading for the Oort cloud and, eventually, interstellar space.

Professional telescopes, on the ground and up in space, will continue to monitor it as long as they can, their images showing it getting steadily and smaller until it eventually fades from their view altogether.

Then, after the last Hubble or JWST image is taken, showing no sign of the comet, we’ll all sit back and begin the wait for the 4^th interstellar object to be discovered.

We probably won’t have to wait long, not with all the automated surveys that are running these days.

I’m sure many of you have been as fascinated by this alien visitor as I have been during its close encounter with our Solar System. I hope some of you managed to see it for yourselves.

I will always treasure those first grainy, light polluted images I took of the comet with my Seestar, down by the river at silly o’clock on a freezing cold November morning, and how thrilling it was to think that the tiny greenish smudge on my phone screen, almost lost in the flaring orange glare of a streetlight, was a comet from another system.

If you took images, no matter how grainy or faint they are, you should treasure them too.

So, farewell Comet 3i ATLAS.

We loved having you in our neighbourhood, and we’re sorry to see you leave.

But it’s comforting – and exciting – to think that there are further adventures ahead of you in the far future, in who knows how many millions or even billions of years’ time, when you pass through another solar system, and are briefly warmed again by another star, far far away.

Did you see or photograph comet 3I/ATLAS? Get in touch and let us know by emailing contactus@skyatnightmagazine.com