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Pa 30 is a nebula surrounding an extremely hot stellar remnant in the constellation Cassiopeia. Its expansion age, position, and unusual properties make it the leading candidate for the remains of supernova SN 1181, an explosion recorded by observers in East Asia. The evidence strongly supports that connection, but the precise kind of stellar explosion and the cause of the remnant’s fast wind are still being studied.
What is Pa 30?
Pa 30 is a nebula and the compact stellar remnant at its center. The system is also catalogued as IRAS 00500+6713; its central star is sometimes called Parker’s star. It is notable because it appears to preserve evidence of a rare supernova that did not completely destroy its star.
Pa 30 was identified in archival infrared data. Later observations revealed a striking pattern of filaments extending radially from the central star. Those features, together with measurements of the nebula’s motion, turned Pa 30 into a candidate for a specific historical event: SN 1181.
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Historical Chinese and Japanese accounts describe a “guest star” seen in 1181. Astronomers have associated those records with Pa 30 because the nebula’s inferred age and sky position fit the event, and its unusual stellar remnant is consistent with a relatively faint, incomplete supernova.
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- Age: Ritter et al. (2021) inferred an expansion age of approximately 1,000 years from the nebula’s expansion.
- Position: Their study placed Pa 30 within 3.5 degrees of the historical position reported in the Chinese and Japanese accounts.
- Expansion evidence: Spectroscopy reported a shock velocity of approximately 1,100 km/s.
These are complementary clues, not a direct observation of the explosion. In a 2024 study using integral-field spectroscopy, researchers mapped Pa 30’s three-dimensional structure and velocities. They found ejecta consistent with ballistic expansion, a cavity inside the remnant, and a sharp inner edge to the filaments that coincides with the outer edge of a bright infrared ring. They also measured a strong asymmetry in the ejecta along the line of sight. The authors concluded: “Our analysis provides strong confirmation that the explosion originated from SN 1181.” (2024 IFU spectroscopy study)
What do the nebula and star look like?
Pa 30 looks different depending on the kind of light used to observe it. Visible-light observations reveal bright, radial filaments associated with heated sulfur. Infrared observations show nebular structure, including a bright ring. X-ray observations show emission from the broader nebula and its central source. These wavelength views reveal different physical features; colors in a processed composite image represent assigned data and should not be read as Pa 30’s appearance to the unaided human eye. NASA describes the system and its multiwavelength imagery in its Pa 30 explainer.
The central star is exceptionally hot. NASA’s 2023 account gives its temperature as about 200,000 degrees Celsius. NASA also reports a central-star wind speed of up to 16,000 km/s. That wind is a distinct phenomenon from the approximately 1,100 km/s shock velocity reported for the nebula by Ritter et al. in 2021: the figures describe different parts of the system and should not be conflated.
How could a supernova leave a star behind?
The leading broad explanation is a subluminous thermonuclear explosion of Type Iax. In this class of event, the explosion may be less energetic and less complete than a typical Type Ia supernova. If the blast fails to unbind all the material, a bound stellar remnant can survive. That makes a surviving central star at Pa 30 compatible with the Type Iax interpretation.
The 2021 identification study proposed that the event arose from a merger of two white dwarfs; NASA’s public explanation also discusses a merger scenario. This is an interpretation of the evidence, not a settled account of exactly how the progenitor system formed or exploded. The historical association is supported by the age, location, and remnant evidence, while the detailed explosion pathway remains an active question.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What might explain Pa 30’s unusually fast wind?
A 2026 study explores one possible explanation: a pure-deflagration explosion could leave carbon-rich material falling back onto the surviving white dwarf. Delayed ignition of that material might then produce the fast wind centuries after the supernova. The model requires a hot post-explosion white-dwarf core near 6 × 108 K; that is a modeled condition, not a directly measured temperature. The authors also discuss a possible helium-star companion.
This is a proposed model, not a confirmed explanation. The 2026 authors state that “the driving mechanism of the fast wind remains uncertain,” and note that other scenarios remain possible. Their work develops the delayed-wind idea without resolving the progenitor or wind mechanism. (Sato et al. (2026), “Delayed wind onset in Pa 30, the remnant of type Iax SN 1181”)
Quick Recap
What is established—and what remains uncertain?
| Question | What observations or studies support | What remains open |
|---|---|---|
| Is Pa 30 the remnant of SN 1181? | Its roughly 1,000-year expansion age and position near the historical reports support the association; the 2024 IFU study calls the evidence strong. | The identification is an evidence-based historical match, not direct observation of the 1181 explosion. |
| What kind of explosion occurred? | A low-luminosity Type Iax thermonuclear event is the leading broad interpretation and can account for a surviving remnant. | The exact progenitor and explosion route are not settled; a white-dwarf merger and a pure-deflagration interpretation appear in published work. |
| What drives the fast wind? | The central-star wind is reported at up to 16,000 km/s by NASA (2023); a 2026 model explores delayed ignition of fallback material. | The wind’s driving mechanism remains uncertain, and the delayed-wind model is not established as the answer. |
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