AD 185

SN 185

The Chinese observation of the guest star of 185

One Chinese phrase decides whether the object stayed visible about eight months or about twenty — depending on whether it means "next year" or "the year after next."

7 December 185, in the Southern Gate

On the sexagenary day gui-hai in the tenth lunar month of Zhongping 2 — conventionally converted to 7 December 185 — Chinese observers recorded the appearance of a "guest star."

They placed it "in the middle of" Nanmen, the Southern Gate asterism in the Centaurus region of the sky. The surviving notice comes through the Book of Later Han, compiled after the event, not from an observing log written that night.

What the record actually says

The received text describes the object with figurative language about its size and changing colours. These are historical descriptions, not calibrated angular-diameter or photometric measurements, and the phrase often rendered "half a bamboo mat" should not be read as a measured disk.

The record says the object diminished and eventually disappeared. The phrase naming the disappearance year has competing translations: about eight months of visibility if hou-nian means the succeeding year, about twenty if it means the year after next.

Probably a supernova

"Guest star" was an observational category, not an ancient diagnosis. A 1994 Nature paper read the record as a comet; a 1995 study proposed that a nova and a comet had been combined; a 2006 reanalysis argued that the absence of reported motion, and the language used elsewhere for comets, make a supernova overwhelmingly more likely.

The probable remnant is RCW 86, about 40 arcminutes across, with shocks measured above 3,000 km/s in its northeast region.

Sources

Researched 23 Aug 2026 6 sources not yet audited Date disputed

How this was checked

Researched from the web into a fact sheet and rewritten from that sheet. This article has not yet had an independent model audit. How the pipeline works →

Date disputed. Sources disagree; the research places it at 0185-12-07.

What the sources leave uncertain

The calendar conversion of the first observation to 7 December 185 is well established, but the astronomical classification is disputed.
A 1994 Nature paper interpreted the record as a comet; a 1995 study proposed that two different observations—a nova and a comet—had been combined.
A 2006 reanalysis argued that the absence of reported motion and the language used elsewhere for comets make a supernova overwhelmingly more likely.
The phrase hou-nian has been translated as the succeeding year, giving about eight months of visibility, or as the year after next, giving about twenty months.