IRAS 00500+6713

IRAS 00500+6713 is the catalogued infrared source for an unusual nebula in Cassiopeia, while the central star has a designation WD J005311, with the whole system designated as Pa 30. The central star and its surrounding shell were created by the supernova seen in the year 1181 (SN 1181) as reported by Chinese and Japanese observers.^[4] Both the nebula and central star have unique and extreme properties, pointing to their creation by a rare type Iax supernova, where two ultra-dense white dwarfs in-spiral to a collision and explosion.^[3]

IRAS 00500+6713 (Pa 30)

2.4 Meter Kitt Peak image of the Pa 30 supernova remnant associated with the SN 1181
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cassiopeia
Right ascension	00h 53m 11.21s[1]
Declination	+67° 30′ 02.4″[1]
Apparent magnitude (V)	15.4[2]
Astrometry
Proper motion (μ)	RA: −2.258[1] mas/yr Dec.: −0.0988[1] mas/yr
Parallax (π)	0.4065±0.0259 mas[1]
Distance	8,000 ± 500 ly (2,500 ± 200 pc)
Details
Mass	1.20±0.17[3] M☉
Radius	0.155[3] R☉
Luminosity	36,000[3] L☉
Temperature	237,000[3] K
Database references
SIMBAD	data

The Pa 30 system was discovered in 2013 by amateur astronomer Dana Patchick.^[5] It was independently discovered by Dr. Vasili Gvaramadze and colleagues who first realized that the central star has extreme properties and proposed that it was created from a merger of two white dwarfs.^[6] The star exhibits record-breaking wind speeds of 16,000 km/s and temperatures near 200,000 K. The central star, might be a rapidly-rotating super-Chandrasekhar white dwarf with a mass ≳1.5 M_☉.

The central star is surrounded by a nebula packed with hot gas and warm dust.^[7] X-ray observations with the XMM-Newton telescope established that the star and its circumstellar nebula are strong X-ray sources. Analysis of X-ray spectra allowed for the first time to determine the chemical composition of the nebula. It was proposed that the nebula is a remnant of a rare type of supernova (SN Iax), and that the SN happened some 1000 years ago.^[3]

It has been linked to the historic supernova SN 1181.^[4] The star is possibly highly unstable, too massive to remain as a white dwarf, and it is predicted to collapse into a neutron star within ten thousand years.^[8]

Both the central star and the nebula contain large amounts of neon, magnesium, silicon, and sulfur (but no hydrogen, helium, or nitrogen), with such requiring an origin in a recent supernova.^[3] The surrounding shell has a unique structure with long radial filaments that have expansion velocities of around 1100 km/s.^[9] Apparently, the filaments are the tattered remains of the original `slow' supernova ejecta, fragmented and streamed into long wakes by the on-going very fast stellar wind emanating from the central white dwarf.

• 
  WISE image of the infrared nebula IRAS 00500+6713, with the central star WD J005311 not visible. The whole system is designated Pa 30
• 
  A comparison between an observed image (left panel; X-ray image (XMM) and IR contours (WISE)) and schematic picture of IRAS 00500+671^[10]