A Comet Woke Up and Turned Green! Comet 220P Is Glowing 20,000 Times Brighter Than Normal
Quick Summary
A comet that is usually invisible without a powerful telescope has suddenly lit up the sky — not once, but twice this year. Comet 220P/McNaught is now glowing bright green, and you might be able to spot it with just a pair of binoculars.
What Happened?
NASA chose today’s Astronomy Picture of the Day to feature something truly surprising: a comet that was not supposed to be doing anything interesting has gone absolutely wild.
Comet 220P/McNaught normally floats through space as a tiny, dim smudge. It is so faint that even skilled astronomers need a powerful telescope to find it. Scientists classify it as a “17th magnitude” object — that is about as faint as something can be and still be detected at all. For 22 years since its discovery, it gave astronomers almost nothing to look at.
Then 2026 arrived, and everything changed.
In late May, Comet 220P erupted — a sudden, explosive brightening that sent it soaring to roughly 8,000 times its normal brightness. That is the difference between a candle and a campfire. Astronomers were stunned. The comet was suddenly visible to the naked eye.
Then in August, it did it again. A second outburst lit the comet up to about 20,000 times its usual brightness. A photograph taken from South Africa shows its head glowing a vivid green color. That green comes from certain carbon-based gases excited by sunlight — the same kind of chemistry that makes neon signs glow at night.
Nobody knows for sure what is causing these dramatic explosions. Scientists think it could be built-up gas bursting out from beneath the surface — like a soda bottle that has been shaken and suddenly opened. Or it could be “comet quakes” — vibrations that crack the surface open. Both outbursts look chemically different from each other, which has surprised scientists even more.
Right now, Comet 220P orbits the Sun between Mars and Jupiter. It circles the Sun once every five and a half years. In October, it will pass within about the same distance as Earth is from the Sun. After that, it is expected to fade and head back to the cold, dark outer solar system.
Why Does It Matter?
Cometss are made of ice, dust, and rock left over from the birth of the solar system about 4.6 billion years ago. They are like frozen time capsules. When a comet has an outburst, it gives scientists a rare window to study what is inside — its chemistry, its structure, and what it is made of.
Comet 220P’s two 2026 outbursts were different from each other. The first was richer in gas. The second was richer in dust. This tells scientists that different layers of the comet contain different materials. Learning why gives us clues about how our solar system formed.
And for regular sky-watchers, this is just a treat. A comet glowing green is genuinely beautiful — and rare. If you have binoculars and a dark sky, now is a great time to look for it in the pre-dawn eastern sky.
Big Words
- Comet — a small, icy body that travels around the Sun; as it gets closer to the Sun, ice turns to gas and forms a glowing cloud and tail
- Outburst — a sudden and dramatic increase in a comet’s brightness, caused by explosive activity on or inside the comet
- Magnitude — the scale astronomers use to measure brightness; lower numbers mean brighter objects
- Perihelion — the point in a comet’s orbit when it is closest to the Sun (Comet 220P reached perihelion on June 14, 2026)
- Coma — the fuzzy, glowing cloud of gas and dust that forms around a comet’s solid core when it is heated by the Sun
Fun Fact
Comet 220P’s green glow comes from a molecule called dicarbon — two carbon atoms bonded together. Sunlight energizes these molecules, and they release that energy as green light. It is essentially the same science that makes glow-in-the-dark toys work!
Think About It
If scientists sent a probe to collect a sample from inside Comet 220P, what do you think they might find — and what could it tell us about the early solar system?
Sources
- NASA Science / APOD — APOD: 2026 August 24 – Comet 220P in Outburst
- TechTimes — Comet 220P/McNaught Erupts Twice: Rozhen Data Show Different Chemistry Each Time
- Daily Galaxy — Watch Comet 220P/McNaught Erupt Into a Brilliant Green Glow
- Virtual Telescope Project — Comet 220P/McNaught: an image – 16 Aug. 2026