Radio and infrared image of IRAS 15103-5754 showing the velocity of the material in the jet.
IRAS 15103-5754, a star observed as it was turning into a planetary nebula, yields new clues as to the death of stars akin to the sun
The birth of planetary nebulae, resulting from the death of low and
intermediate mass stars, is usually thought of as a slow process, in
contrast with the intense supernovae that massive stars produce. But a
recent study led by researchers at the Institute of Astrophysics of
Andalusia (IAA-CSIC) in collaboration with the Center for Astrobiology
(CAB, CSIC/INTA) has revealed the fact that explosive phenomena also
intervene in the formation of planetary nebulae.
"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. 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”, says José Francisco Gómez, IAA-CSIC researcher
in charge of the project.
The study of IRAS 15103-5754, part of a group of sixteen objects known
as ‘water fountains’, has yielded important clues concerning this final
stage. ‘Water fountains’ are mature stars in a state of transition from
red giants to planetary nebulae which display jets of ejected material
that can be detected from intense radiation produced by water vapor
molecules (water maser emission).
IRAS 15103-5754 stands out within the small group under study because
it has been observed that the velocity of the material inside the jet
increases in proportion to the distance from the central star. "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”, says Luis F. Miranda (IAA-CSIC,
University of Vigo). “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”. 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”, says
José Francisco Gómez (IAA-CSIC).
This study has established the importance of ‘water fountains’ in
understanding how the symmetry of stars is broken in the final stages of
their lives, and thus to shed light on the outstanding variety of
planetary nebulae that we encounter.
Reference:
José F. Gómez et al. "The first water fountain collimated outflow in a planetary nebula". The Astrophysical Journal. DOI: 10.1088/0004-637X/799/2/186
Contact:
Instituto de Astrofísica de Andalucía (IAA-CSIC)
Unidad de Divulgación y Comunicación: http://www-divulgacion.iaa.esSilbia López de Lacalle - sll@iaa.es - 958230532
