No one alive today will see this comet again
Once every eighty thousand years, a frozen wanderer from the outermost reaches of the solar system passes close enough to Earth for human eyes to find it. Comet Tsuchinshan-ATLAS — dubbed the 'comet of the century' by the Royal Astronomical Society — is making that passage now, and this weekend offers Northern Hemisphere observers their final, optimal window before the comet fades beyond sight and recedes into the deep dark for another eighty millennia. In the long arc of cosmic time, this is a brief and unrepeatable gift.
- The window is closing fast — Tsuchinshan-ATLAS is dimming as it retreats from the Sun, and after this weekend the fading will accelerate beyond recovery.
- A rare convergence is briefly working in skywatchers' favour: the comet sets later each evening, climbing higher into darker skies and temporarily offsetting its own dimming.
- Observers across the Northern Hemisphere are being urged to face southwest at sunset and look near Venus — clear skies this weekend could deliver the best comet viewing since 1997.
- A second 'Halloween comet', discovered only in late September, may also appear in late October, but it risks complete disintegration during its dangerously close solar pass on October 28 — an all-or-nothing celestial gamble.
- Both comets are thought to originate from the Oort Cloud, an invisible reservoir of billions of icy bodies surrounding the solar system — ancient debris from the moment the planets were born.
If you have been meaning to look up at the night sky, this weekend may be your last real chance for eighty thousand years. Comet Tsuchinshan-ATLAS has been visible over the UK for the past week, but astronomers are urging observers to act now — the window is closing, and when it does, no one alive today will ever see this comet again.
The timing works briefly in viewers' favour. Each evening the comet sets a little later, climbing higher into the sky as darkness falls. It is losing brightness as it travels away from the Sun, but that loss is being temporarily offset by the advantage of darker skies. Once the next few days pass, the fading will accelerate and that advantage will vanish with it. For Northern Hemisphere skywatchers, clear skies this weekend could deliver the finest comet viewing since 1997. The Royal Astronomical Society has christened it the 'comet of the century' for its exceptional brightness and near-global visibility. Observers should look toward the southwest at sunset, near Venus.
A second comet is also in play. Discovered on September 27 and nicknamed the 'Halloween comet', C/2024 S1 (ATLAS) may appear low in the eastern sky before sunrise, and after swinging around the Sun on October 28, could reappear in the western sky around Halloween itself. But comets are fragile things. This one passes so close to the Sun that it may simply disintegrate during the encounter. Astronomer Dr. Qicheng Zhang of Lowell Observatory has described it as 'almost a binary all-or-nothing event.'
Both comets are ancient remnants from the Oort Cloud — an invisible reservoir of billions of icy bodies surrounding the solar system, extending trillions of miles into deep space. Astronomers cannot see it directly, but its existence is the only explanation for how certain comets periodically arrive in our skies. For Tsuchinshan-ATLAS, the mathematics are clear: this weekend is the moment. The next visitor like it will not return until the year 82024.
If you've been meaning to look up at the night sky, this weekend might be your last real chance for eighty thousand years. Comet Tsuchinshan-ATLAS has been visible over the UK for the past week, but astronomers are urging observers to act now. The window is closing, and when it does, no one alive today will see this comet again.
The timing works in viewers' favor for the next few days, even as the comet itself grows dimmer. Each evening, it sets later, which means it climbs higher into the sky at sunset and after dark falls. The comet is losing brightness as it travels away from the Sun, but that loss is being offset—at least temporarily—by the advantage of darker skies. According to observers tracking the phenomenon, this convergence of factors creates the optimal viewing window. After the next few days pass, the fading will accelerate and the dark-sky advantage will fade with it.
For Northern Hemisphere skywatchers, clear skies this weekend could deliver the finest comet viewing since 1997. The Royal Astronomical Society has christened Tsuchinshan-ATLAS the "comet of the century" because of its exceptional brightness and the fact that it's visible across most of the planet. From the Northern Hemisphere, observers should look toward the southwest at sunset; the comet is expected to appear near Venus. Its position just north of the celestial equator means that much of Earth has a reasonable shot at seeing it.
A second comet is also in play. Designated C/2024 S1 (ATLAS), this one was discovered only on September 27 and has earned the nickname "Halloween comet" because of its expected visibility late in October. It may appear low in the eastern sky just before sunrise, and after swinging around the Sun on October 28, it could reappear in the western night sky around Halloween itself. But there's a catch: comets are fragile things. This one passes so close to the Sun that it may simply disintegrate during the encounter. Dr. Qicheng Zhang, an astronomer at Lowell Observatory in Arizona who is monitoring the comet, told Forbes that the nucleus could be completely destroyed by the heat. "Only if the nucleus survives past that point will there be any sort of display worth mentioning," he said. "It's almost a binary all-or-nothing event."
Comets are ancient remnants—frozen balls of gas, dust, and rock left over from the formation of the solar system 4.6 billion years ago. When one approaches the Sun, the ice melts and vaporizes, creating the characteristic glowing head and tail that can dwarf most planets. Both of this month's comets are thought to originate from the Oort Cloud, an invisible cosmic reservoir that surrounds the Sun and extends trillions of miles into deep space. Astronomers cannot see the cloud directly; its particles are too thinly scattered and too far from any star. But they know it must be there because it's the only explanation for how certain classes of comets periodically arrive in our solar system. The cloud is believed to contain billions of icy bodies, a vast freezer of celestial wanderers waiting in the dark.
For Tsuchinshan-ATLAS, the mathematics are clear: this is the moment. Look this weekend if you can. The next visitor from the Oort Cloud will arrive in the year 82024.
Notable Quotes
Only if the nucleus survives past that point will there be any sort of display worth mentioning. It's almost a binary all-or-nothing event.— Dr. Qicheng Zhang, astronomer at Lowell Observatory, on the Halloween comet's chances of surviving its close approach to the Sun
The Hearth Conversation Another angle on the story
Why does this comet matter more than the others we've seen?
It's not just that it's bright—though it is. It's that it's accessible. You don't need a telescope. And the Royal Astronomical Society doesn't hand out the "comet of the century" label lightly. The last time most people could see something this good was 1997.
So if I miss this weekend, I've genuinely missed it?
For eighty thousand years, yes. That's not hyperbole. This comet's orbit is so long that by the time it comes back, human civilization will be unrecognizable. Your great-great-grandchildren's descendants won't see it.
What about the Halloween comet? That sounds like a backup plan.
It could be. But it's also a gamble. It might disintegrate when it gets too close to the Sun. The astronomer monitoring it called it "all-or-nothing." You could wake up on Halloween and find there's nothing to see.
Where exactly do these things come from?
The Oort Cloud—this invisible shell of icy bodies that surrounds our entire solar system, extending trillions of miles out. We can't see it, but we know it's there because comets keep arriving from it. It's like a cosmic freezer we didn't build.
And they've been there since the solar system formed?
Since the beginning, yes. 4.6 billion years. These are leftovers from when everything was still being assembled. When one of them gets nudged toward the Sun, we get a show.
So this weekend is genuinely the last chance?
For this comet, in this lifetime, yes. Clear skies and a southwest view. That's all you need.