 Size comparison of Draugr with Earth. (Based on selected hypotheticalmodeled compositions) | |
| Discovery | |
|---|---|
| Discovered by | |
| Discovery site | United States[1] |
| Discovery date | 22 April 1994 |
| Pulsar Timing | |
| Orbital characteristics | |
| 0.19 AU (28,000,000 km)[2] | |
| Eccentricity | 0.0[2] |
| 25.262 ± 0.003[2]d | |
| Inclination | 50[2][note 1] |
| 2,449,765.6 ± 0.2[2] | |
| Star | Lich |
| Physical characteristics | |
| 0.338R🜨 | |
| Mass | 0.020 ± 0.002[2][note 1]M🜨 |
| Temperature | 266 K (−7 °C; 19 °F)[3] |
PSR B1257+12 b, alternatively designatedPSR B1257+12 A, also namedDraugr, is anextrasolar planet approximately 2,300light-years (710 pc) away[4] in theconstellation ofVirgo. The planet is the innermost object orbiting thepulsarLich, making it apulsar planet in the dead stellar system. It is about twice as massive as theMoon, and is listed as theleast massive planet (with the mass accurately determined) known, including among the planets in theSolar System.[1]
The convention that arose for designating pulsars was that of using the letters PSR (Pulsating Source of Radio) followed by the pulsar'sright ascension and degrees ofdeclination. The modern convention prefixes the older numbers with a B meaning the coordinates are for the 1950.0epoch. All new pulsars have a J indicating 2000.0 coordinates and also have declination including minutes. Pulsars that were discovered before 1993 tend to retain their B names rather than use their J names, but all pulsars have a J name that provides more precise coordinates of its location in the sky.[5]
On its discovery, the planet was designated PSR 1257+12 A and later PSR B1257+12 b. It was discovered before the convention that extrasolar planets receive designations consisting of the star's name followed by lower-caseRoman letters starting from "b" was established.[6] However, it is listed under the latter convention on astronomical databases such asSIMBAD and theExtrasolar Planets Encyclopedia. Hence the designation PSR B1257+12 b.
In July 2014, theInternational Astronomical Union launchedNameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.[7] The process involved public nomination and voting for the new names.[8] In December 2015, the IAU announced the winning name was Draugr for this planet.[9][10] The winning name was submitted by the Planetarium Südtirol Alto Adige inKarneid,Italy.Draugr areundead creatures inNorse mythology.[11]
Media related toPSR B1257+12 A at Wikimedia Commons| Preceded by | Least massive known exoplanet 1994–2013 | Succeeded by |
