 Infrared images from NASA'sSpitzer Space Telescope andWISE are combined with X-ray data from theChandra X-ray Observatory and ESA'sXMM-Newton Observatory in this image of RCW 86. | |
| Event type | Supernova remnant,supernova  |
|---|---|
| Type Ia? | |
| Date | 7 December 185 |
| Constellation | Circinus andCentaurus |
| Right ascension | 14h 43m |
| Declination | −62° 30′ |
| Epoch | J2000 |
| Galactic coordinates | G315.4−2.3 |
| Distance | 2,800 pc (9,100 ly)[1] |
| Remnant | Shell |
| Host | Milky Way |
| Notable features | Ancient records of SN 185 may be the earliest written description of a supernova. |
| Peakapparent magnitude | "as much as −8"[2] |
| Other designations | SN 185, SNR G315.0-02.3, SNR G315.4-02.3, 1ES 1436-62.4, 1RXS J144254.3-622815, 3FHL J1443.0-6227e, AJG 27, 3A 1438-626, GPS 1438-624, MSH 14-6-03, 2FHL J1443.2-6221e |
| Preceded by | None known |
| Followed by | SN 386 |
SN 185 was atransient astronomical event observed in the yearAD 185, likely asupernova. The transient occurred in the direction ofAlpha Centauri, between the constellationsCircinus andCentaurus, centered atRA14h 43mDec −62° 30′, in Circinus. This "guest star" was observed byChinese astronomers in theBook of Later Han (後漢書),[3] and might have been recorded inRoman literature.[2] It remained visible in the night sky for eight months. This is believed to be the first supernova for which records exist.
The Book of Later Han gives the following description:
In the 2nd year of the epoch Zhongping [中平], the 10th month, on the day Guihai [癸亥] [December 7, Year 185], a 'guest star' appeared in the middle of theSouthern Gate [南門] [an asterism consisting ofε Centauri andα Centauri], The size was half a bamboo mat. It displayed various colors, both pleasing and otherwise.[4] It gradually lessened. In the 6th month of the succeeding year it disappeared.[5]
The gaseous shellRCW 86 is probably thesupernova remnant of this event and has a relatively large angular size of roughly 45 arc minutes[1] (larger than the apparent size of the full moon, which varies from 29 to 34 arc minutes). The distance to RCW 86 is estimated to be 2,800parsecs (9,100light-years).[1] Recent X-ray studies show a good match for the expected age.[6]
Infrared observations from NASA'sSpitzer Space Telescope andWide-field Infrared Survey Explorer (WISE) reveal how the supernova occurred and how its shattered remains ultimately spread out to great distances. The findings show that the stellar explosion took place in a hollowed-out cavity, allowing material expelled by the star to travel much faster and farther than it would have otherwise.[7]
Differing modern interpretations of the Chinese records of the guest star have led to quite different suggestions for the astronomical mechanism behind the event, from acore-collapse supernova[7] to a distant, slow-moving comet[8] – with correspondingly wide-ranging estimates of its apparent visual magnitude (−8 to +4). The recentChandra results suggest that it was most likely aType Ia supernova (a type with consistent absolute magnitude),[7][9] and therefore similar toTycho's Supernova (SN 1572), which had apparent magnitude −4 at a similar distance.
