Shrimp Nebula: The Star That Died at 125 km/s — and Left Behind the Most Lopsided Nebula in the Sky

A dead star is sprinting through our galaxy at 125 kilometres per second right now. It has been running for tens of thousands of years. And the ghost of what it used to be — a glowing cloud of ionised gas several light-years wide — is being carved into the shape of a shrimp by the sheer force of its own velocity.

Today, NASA's Astronomy Picture of the Day pointed its lens at it. Astronomers call it Sh2-188. The internet is calling it the Shrimp Nebula. Once you see the image, you'll understand both names instantly.

And here's the part that should make you feel something: this star lived a life not unlike our Sun. Then it ran out of fuel, swelled into a red giant, shed its outer layers, and left behind a hot, dense white dwarf smaller than the Earth. That's the stellar corpse now speeding through the constellation Cassiopeia, about 850 light-years from where you're reading this.

What is the Shrimp Nebula?

Sh2-188 is a planetary nebula — one of the most misleadingly named objects in astronomy. Despite the name, it has nothing to do with planets. It's what you get when a mid-sized star like our Sun reaches the end of its life: the outer layers are blown off into space as an expanding shell of glowing gas, while the core collapses into a white dwarf that slowly cools over billions of years.

The designation "Sh2-188" comes from astronomer Stewart Sharpless, who catalogued it in 1959 alongside hundreds of other emission nebulae. For decades it looked like just another entry in a list. Then astronomers started measuring its proper motion — how fast and in what direction the central star was actually moving through space. The answer changed everything about how they understood its shape.

Why does it look like a shrimp?

Most planetary nebulae puff outward fairly symmetrically — concentric glowing rings, like smoke rings in space. Sh2-188 looks nothing like that. It has a bright, dense arc on one side, and on the other the glow fades into almost nothing.

The reason is simple and stunning: the star is moving. As the white dwarf sprints through the interstellar medium — the thin gas and dust filling the space between stars — it creates a shockwave at its leading edge. The ejected gas piles up there, compressed and superheated, glowing brightly. On the trailing side, the gas disperses into the void, too thin to shine.

It's the same reason a boat's bow wave is visible at the front but not the back. Except instead of water, this is ionised hydrogen. And instead of a boat, it's a stellar corpse the size of Earth, still hot enough to glow blue-white, moving at a speed that could take it from Earth to the Moon in under an hour.

How fast is 125 km/s in real terms?

The International Space Station orbits at about 7.66 km/s — we call that astonishingly fast, and it is. You can watch it cross the entire night sky in under six minutes. Track it live right now on the SkyLens live tracker if you want a sense of what that speed looks like from the ground.

The central star of Sh2-188 is moving at more than 16 times that speed relative to its surrounding gas. Voyager 1 — humanity's most distant spacecraft, now more than 24 billion kilometres from Earth — travels at roughly 17 km/s in interstellar space. This dead star is about seven times faster even than that.

At 125 km/s, you'd cross the Atlantic Ocean in under a minute. You'd circle the entire Earth in about five and a half minutes.

Is this what happens to our Sun?

In about five billion years: roughly, yes.

Our Sun will exhaust its hydrogen fuel, swell into a red giant that swallows Mercury and Venus — and possibly Earth — then shed its outer layers in pulses of stellar wind. What remains will be a white dwarf: smaller than Earth, about as massive as today's Sun, cooling over trillions of years. The ejected material will glow as a planetary nebula for perhaps 10,000 years before dispersing completely into the interstellar medium.

Whether that nebula will look like Sh2-188 depends on how fast the Sun is moving through its local neighbourhood at the time. Right now, the Sun moves at about 20 km/s relative to nearby stars — a gentle drift compared to Sh2-188's sprint. Our nebula might be more symmetrical. Less dramatic. Slightly less like a shrimp.

Why is Sh2-188 in the APOD today?

NASA's Astronomy Picture of the Day — published every single day since June 1995 — selected Sh2-188 for September 29, 2026. The image shows the lopsided arc in extraordinary detail: a bright crescent of compressed ionised gas on one side, with wisps and filaments trailing off where the material has had tens of thousands of years to spread into the void.

It is one of roughly 40 known bowshock planetary nebulae — cases where proper motion through the ISM is the primary force shaping the structure. Most planetary nebulae are shaped by binary companions, magnetic fields, or the original star's rotation. Sh2-188 is shaped by raw, sustained speed. Scientists sometimes call objects like this "running nebulae." The shrimp shape isn't a coincidence. It's a physics lesson written in light.

Does this tell us anything about where dead stars end up?

It tells us quite a lot. The speed of this white dwarf — far higher than the average stellar velocity in our part of the galaxy — suggests it may have been given a gravitational kick at some point in its past. Perhaps from a close encounter with another star. Perhaps from the asymmetric mass ejection during its death throes. Astronomers are still working out the exact history. What's certain is that it's been sprinting ever since.

The nebula itself won't last. In another 10,000 to 20,000 years, the gas will disperse completely into the interstellar medium — seeding it with enriched elements forged in the star's nuclear furnace over billions of years. The oxygen, carbon, nitrogen. Swept into the galaxy by a dead star still running from nothing in particular. For a deeper look at how this kind of stellar recycling works, explore the SkyLens astronomy explainers.

What happens to the white dwarf after the nebula disappears?

It just keeps running. And cooling. White dwarfs don't explode on their own — without a companion star feeding them mass, they simply cool over timescales longer than the current age of the universe. The nebula will vanish in tens of thousands of years. But the white dwarf will still be out there in Cassiopeia, a dark planet-sized ember, still moving at 125 km/s, long after there's no glowing cloud left to tell anyone it ever had a life.

That's the part worth sitting with for a minute. The death is beautiful. The aftermath is silence.

This is just one of the thousands of extraordinary objects mapped across our sky — and compared to the debris fields, constellations, and active satellites you can watch in real time, it's a reminder of the scale we're embedded in. Browse more stories on the SkyLens blog.