The death of low and intermediate mass stars produces planetary nebulae, which is thought to be part of a slow process - slower than the supernovae that higher mass stars produce, but a recent study suggests that the lower mass explosions have just as much chutzpah as the big guys.
The study was conducted by researchers at the Instituto de Astrofísica de Andalucía (IAA-CSIC) in Granada, Spain who collaborated with the Center for Astrobiology (CAB, CSIC/INTA) in Madrid, Spain
"In a few thousand million years, the sun will exhaust its nuclear fuel, expand into a red giant and eject a major part of its mass," said IAA-CSIC researcher José Francisco Gómez, according to a press release from the IAA-CSIC. "The final result will be a white dwarf surrounded by a glowing planetary nebula. Even though every star with a mass below ten solar masses goes through this short but important final transition, many details of the process still evade us."
IRAS 15103-5754 is part of a grouping of 16 objects called "water fountains" (WFs), and the study of this group has provided some understanding of the terminal stages of stars. WFs result from stars phasing from red giants to planetary nebulae. The WFs shoot out material detected from the intense radiation caused by water vapor molecules - or water maser emission.
"Moreover, the velocity distribution of the maser emission shows a "Hubble-like" flow (higher velocities at larger distances from the central star), consistent with a short-lived, explosive mass-loss event," researchers wrote. "This velocity pattern is not seen in other WFs (which are presumably in earlier evolutionary stages). We therefore suggest that we are witnessing a fundamental change of mass-loss processes in WFs, with water masers being pumped by steady jets in post-AGB stars, but tracing explosive/ballistic events as the object enters the PN phase."
"Water molecules are generally destroyed soon after the planetary nebula is formed, and in the rare cases where a maser emission has been detected, the velocity has always been very low", said IAA-CSIC and University of Vigo affiliated Luis F. Miranda in the press release. "In IRAS 15103-5754 we are seeing for the first time a water maser emission at velocities of hundreds of kilometers per second. We are witnessing the transition of a star into a planetary nebula in real time".
"The high velocity can only be explained by the occurrence of an explosion," said Gómez, according to the press release. "Our results show that, contrary to the most widespread theories, when a star turns into a planetary nebula an enormous explosion is produced - short-lived but highly energetic - which will determine the evolution of the star in its last phases of life."
