The NASA NuSTAR mission unveils processes in supernova explosions of stars

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In June 2012, the NASA NuSTAR (Nuclear Spectroscopic Telescope Array) mission deployed the first space telescope with an optic able to focus high energy X-rays (3-79 keV). Today, NuSTAR offers the mapping of the rest of the supernova Cassiopeia A. The interpretation of the results led to a publication in Nature, on February 20, 2014, to which the IRAP (CNRS / University of Toulouse III), with the support of the CNES, is associated.

The first map of radioactive material (blue) contained in the remnant of a supernova, drawn by the NuStar mission in the field of high energy X-rays. Image Credit: NASA / JPL-Caltech / CXC / SAO

The explosion of a star in a supernova still today remains a process partly unknown to the astronomers. In order to solve the mystery, the NuSTAR mission has just drawn the very first map of radioactive material in the remnants of the supernova Cassiopeia A (Cas A).

Cassiopeia A results from the supernova explosion of a massive star, some 11,000 years ago. From this massive star only remain an extremely dense stellar remnant (a neutron star) and the ejecta material. Only the stars with a mass greater than 8 solar masses explode at the end of their life. During the explosion, metals such as iron, titanium and calcium are thrown to space. Without supernovae, these chemical elements, essentials for our life, would not be available.

The observation and the understanding of supernova remnants is one of the main objectives of the mission. NuSTAR has just provided the first map of the distribution of Titanium: a material created at the heart of the explosion. The Titanium distribution tells us about the different stages of the explosion of the star. The NuSTAR results show that the star would have been shaken, re-energizing the shock wave associated with the explosion. This wave would have the effect of expelling the outer layers of the star, producing asymmetries in the distribution of titanium observed by NuSTAR.

These illustrations show the progression of a supernova blast. A massive star (left), which has created elements as heavy as iron in its interior, blows up in a tremendous explosion (middle), scattering its outer layers in a structure called a supernova remnant (right). Image Credit: NASA/CXC/SAO/JPL-Caltech

The X-ray radiography of the supernova remnants provides a direct diagnosis of the explosion mechanism and information complementary to the observations of heavy elements such as iron, which are heated.

These latter observations are carried out at X-ray lower energies, with the Chandra and XMM-Newton observatories. It remains to understand why the spatial distributions of the metals differ, although elements such as titanium and iron are produced simultaneously during the explosion. “Cassiopeia A has therefore not delivered its ultimate secrets, but NuSTAR has already opened a new window on the mechanism of explosion of massive stars,” says Matteo Bachetti, one of the IRAP researchers heavily involved in the NuSTAR mission and specialist of the X binaries and X ultra-light sources.

Source :

“Asymmetries in core-collapse supernovae from maps of 44Ti emission in Cassiopeia A” by B. W. Grefenstette, F. A. Harrison et al.

Links :

  • NASA Press Release :
  • La mission NuSTAR :

IRAP Contacts :

  • Matteo Bachetti,
  • Didier Barret,



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