Medieval ‘guest star’ reveals its secrets after nearly 850 years
Warwick astronomers are part of an international team to reveal the most detailed view yet of Pa 30, the likely remnant of a supernova documented in 1181. The new observations reveal that its famous ‘firework’ filaments are not smooth streaks, but chains of tiny knots.
In August 1181, Chinese, Japanese and Arabic astronomers recorded the sudden appearance of a bright new 'guest star' in the constellation now known as Cassiopeia. It stayed visible for 185 days.
More than eight centuries later, images from the Gemini North telescope on Maunakea in Hawaiʻi have revealed Pa 30, the likely remains of that explosion, in unprecedented detail. They show about ten times more filamentary structure than previously seen.
The analysis of the images, led by Dr Timothy Cunningham at the University of Warwick with international colleagues, is published in The Astrophysical Journal. It shows that the remnant's firework-shaped ejecta is made of chains of tiny gas knots rather than smooth streaks, as previously thought. This suggests thermal or density variations in the material surrounding the star shaped the ejecta as it expanded away from the explosion.
Dr Timothy Cunningham, Assistant Professor and STFC Ernest Rutherford Fellow, University of Warwick said: “These images give us the clearest picture yet of Pa 30's structure, and it's not what we expected. The filaments are made of chains of tiny knots rather than smooth streaks, providing new constraints on the nature of the space around the star before it exploded and the physical processes that have shaped the expanding ejecta. It's rare to get this level of detail on a supernova we can date to a specific week in history.”
SN 1181 is one of only five supernovae in the Milky Way known to have been observed from Earth before the invention of the telescope. Eight separate texts record the sighting between 4 and 6 August 1181. At the time, the Genpei War was being fought in Japan, Henry II was on the throne of England, and the new star was even addressed in a poem to Saladin, the first sultan of Egypt and Syria.
Pa 30, a blue central star surrounded by a firework-shaped shell, is the top candidate for the supernova remnant. Surviving stars are normally 'kicked' away by a supernova explosion, but the central star of Pa 30 sits almost exactly at the centre. This implies a highly symmetrical explosion that did not send the star off course.
The findings add to evidence that SN 1181 was a rare Type Iax supernova. Unlike standard Type Ia explosions, which destroy their stars, Type Iax events are lower-energy, incomplete explosions that leave a surviving star. Pa 30 is the only known Type Iax remnant in the Milky Way.
Celestial events carried powerful meaning for medieval societies. The Bayeux Tapestry shows Halley's Comet in 1066, followed by a messenger warning King Harold II, linking the sign in the sky to his downfall. The story of the 1181 supernova is one of humans working together, across time and space, to understand the changing Universe.
ENDS
Notes to Editors
Analysis of this data is presented in a paper titled “Detection of knots in the supernova type Iax remnant Pa 30” appearing in The Astrophysical Journal. DOI: 10.3847/1538-4357/ae9cb2
This research was led by Timothy Cunningham (University of Warwick / Center for Astrophysics (CfA) - Harvard & Smithsonian) and Ilaria Caiazzo (Institute of Science and Technology Austria) alongside J. C. Raymond (CfA), and S. J. Kenyon (CfA).
The images were captured with the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab.
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Images
A – Supernova remnant Pa 30
No, this is not a firework display. This is Pa 30 — the likely remnant of the historic supernova witnessed in the year 1181, now captured here in unprecedented detail by the Gemini North telescope, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab. This image was captured with the Gemini Multi-Object Spectrograph (GMOS), and it shows that the remnant’s unmistakable firework-shaped ejecta take on a cascading knot-like structure.
Credit: International Gemini Observatory/NOIRLab/NSF/AURA
Acknowledgment: PI: T. Cunningham (Center for Astrophysics — Harvard & Smithsonian; now University of Warwick)
Image Processing: J. Miller & M. Rodriguez (International Gemini Observatory/NSF NOIRLab), T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), D. de Martin & M. Zamani (NSF NOIRLab)
B – Gemini North’s laser shines through airglow DSC06245
The Gemini North telescope’s laser guide star beams up into the atmosphere, backdropped by the mesmerizing green wash of airglow. The laser guide star is used to measure turbulence in the Earth’s atmosphere so the telescope can correct for it and achieve clear images of the night sky. Airglow is faint light emitted by atoms in the upper atmosphere that have been excited by the Sun’s ultraviolet radiation.
Gemini North is one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab, and is located on Maunakea in Hawai’i.
Credit: International Gemini Observatory/NOIRLab/NSF/AURA/M. Rodriguez (International Gemini Observatory/NSF NOIRLab)
About Pa 30
Pa 30 was only discovered in 2013 through a citizen science campaign to find planetary nebulae in Wide-field Infrared Survey Explorer (WISE) data. It was the 30th nebula found by American amateur astronomer Dana Patchick. Follow-up imaging on the KPNO 2.1-meter Telescope and the Hiltner 2.4-meter Telescope, both located at NSF Kitt Peak National Observatory (KPNO), a Program of NSF NOIRLab, revealed faint, diffuse nebular emission and remarkable radial filaments threading the nebula in a nearly perfect sphere. Based on its estimated age and brightness, scientists consider Pa 30 to be the likely remnant of SN 1181.
Pa 30 is unique among all known supernova remnants because the central star remaining after the explosion, IRAS 00500+6713, is extremely hot, with a temperature of about 200,000°C (~360,000°F). It also possesses very fast stellar winds that move at around 16,000 kilometers per second (~10,000 miles per second).
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About NSF NOIRLab
NSF NOIRLab, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona.
Note: The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community.