| May 12, 2015||Asymmetric explosion of SN1987A from 44Ti emission lines revealed with NuSTAR|
The NASA's high-energy X-ray observatory Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the supernova 1987A (SN1987A) allowed to resolve the 67.87 and 78.32 kiloelectron volt emission lines from decay of 44Ti produced in the supernova explosion. NuSTAR data showed that these two lines are narrow and redshifted with a Doppler velocity of ~700 kilometers per second, probing direct evidence of large-scale asymmetry in the explosion.
"Stars are spherical objects, but apparently the process by which they die causes their cores to be turbulent, boiling and sloshing around in the seconds before their demise," said Steve Boggs of the University of California, Berkeley, lead author of a new study on the findings, appearing in the May 8 issue of Science. "We are learning that this sloshing leads to asymmetrical explosions."
"Titanium is produced in the very heart of the explosion, so it traces the shape of the engine driving the disassembly of the star," said Fiona Harrison, the principal investigator of NuSTAR at the California Institute of Technology in Pasadena. "By looking at the shift of the energy of the X-rays coming from titanium, the NuSTAR data revealed that, surprisingly, most of the material is moving away from us."
Last year, NuSTAR created detailed 44Ti maps of another supernova remnant, called Cassiopeia A, also finding evidence of an asymmetrical explosion, though not to as great an extent as in 1987A. Together, these results suggest that lopsidedness is at the very root of core-collapse supernova.
NuSTAR brought a new tool to the study of supernovae. Thanks to the observatory's sharp high-energy X-ray vision, it has made the most precise measurements of 44Ti yet. This radioactive material is produced at the core of a supernova, so it provides astronomers with a direct probe into the mechanisms of a detonating star.
The Italian participation to NuSTAR includes the provision of the Malindi ground station (ASI), the ASI Science Data Center (ASDC), which contributes with the development of the NuSTARDAS software package and hosting an official mirror of the NuSTAR scientific public data archive, and a team of scientists of the Istituto Nazionale di Astrofisica (INAF) that actively collaborates on the primary scientific mission goals.
The NuSTAR team at ASDC is composed by M. Perri (INAF archive scientist), S. Puccetti (INAF archive scientist) and P. Giommi (ASDC Responsible).
For more details on NuSTAR, see:
Right: 59-80 keV NuSTAR spectrum of SN1987A with detected 44Ti emission lines. The observations indicate that supernovae belonging to a class called Type II or core-collapse blast apart in a lopsided fashion, with the core of the star hurtling in one direction, and the ejected material mostly expanding the other way (see model diagram at left).
[Credit: NASA/JPL-Caltech/UC Berkeley]