Sakurai's Object (V4334 Sgr)
Fr.: objet de Sakurai
A → post-asymptotic giant branch star that in 1995 underwent sudden re-brightening due to a → helium shell flash, or → very late thermal pulse (VLTP), before embarking on a → white dwarf cooling track. Such an outburst is very rare, and in this case it is the first seen in modern times. Stellar outbursts observed in 1670 (nova CK Vul) and 1918 (nova V605 Aql) may have been caused by the same phenomenon. Since 1995, Sakurai's Object has undergone observable changes on time-scales of weeks to months. Several phases of dust production followed the outburst, with a deep optical minimum beginning in early 1999, such that any changes in the central star have since been inferred from radio and infrared observations. Subsequent observations and modeling have revealed much about the dust shell formation and the outer regions of the ejecta. This object is also the central star of an extended very faint planetary nebula (→ CSPN), confirming that the latest large mass ejection during the planetary nebula phase occurred several thousands years ago (see, e.g. H. L. Worters et al. 2009, MNRAS 393, 108 and references therein).
Named after Yukio Sakurai, a Japanese amateur astronomer, who serendipitously discovered it on February 20, 1996, when searching for comets; → object.