New puzzle for astronomers who discover a new object within a dead star

UNSW Canberra researchers are closer to understanding how stars evolve and explode as supernovae, producing elements necessary for forming life on Earth.

Dr. Ashley Ruiter, Australian Research Council Future Fellow at the School of Physical, Environmental and Mathematical Sciences, UNSW Canberra.
Dr. Ashley Ruiter, Australian Research Council Future Fellow at the School of Physical, Environmental and Mathematical Sciences, UNSW Canberra.

Scientists have discovered the X-ray emitting neutron star in an approximately 2,000-year-old supernova remnant in the Small Magellanic Cloud, a satellite dwarf galaxy of our own Milky Way. The team came across the discovery as they were investigating several significant and unsolved problems in astrophysics: how do massive stars evolve to form a particular type of supernova, how do these supernovae explode, and what elements are produced in these explosions?

Dr. Ivo Rolf Seitenzahl, Australian Research Council Future Fellows at the School of Physical, Environmental and Mathematical Sciences, UNSW Canberra said, “A large portion of life on Earth is composed of the chemical elements produced in supernova explosions. We are still learning details about our origins – in particular, how dying massive stars explode and produce elements such as oxygen, neon, and sulfur.”

Encompassing the neutron star, the group distinguished a torus of moderately icy – roughly room temperature – gradually extending gas, comprising overwhelmingly of oxygen and neon. It is the first time that such a structure is recognized in the region of this sort of secluded neutron star. This is yet another showing of the energy of vital field spectroscopic perceptions to find new aspects of the Universe.

The study was carried out using The Multi-Unit Spectroscopic Explorer (MUSE) instrument at the 8.4m Very Large Telescope at Cerro Paranal in Chile. MUSE covers a 1arcmin x 1arcmin area with roughly 90,000 spatial pixels, each recording a spectrum independently. MUSE couples the discovery potential of an image with the measuring capabilities of a spectrograph, producing a 3-dimensional data “cube”, capturing both the spatial and wavelength information at high resolution.

Dr. Ashley Ruiter, Australian Research Council Future Fellows at the School of Physical, Environmental and Mathematical Sciences, UNSW Canberra said, “the fact that the supernova explosion left behind a neutron star, and not a black hole is an interesting discovery in itself. It is still unknown which stars leave behind one or the other.”

“A black hole is much harder to detect. Actually, without any detection, one could say maybe it actually left behind a black hole, or that the neutron star is just not detectable. But, this study provides a direct link between the detected remnant – a neutron star – and its predecessor, the progenitor star. Making such links helps us better understand the explosion mechanisms of supernovae.”

Dr. Seitenzahl added, “The identification of the neutron star is only the beginning. The origin of the associated torus, with oxygen, neon, and carbon emission, is still quite puzzling.”

“Though it surrounds the cooling neutron star, we have not yet conclusively found an explanation for the origin of the torus. We’re quite sure that it is almost certainly related to the supernova explosion and the formation of the neutron star, however, we are still unclear about when, how, and why the torus was formed.”

Dr. Ruiter explained, “The morphology of material in the neutron star’s vicinity hints that, maybe, this neutron star’s precursor was once very close to another star.”

“Single stars usually behave in ways that are easy to predict. However, there is evidence from other studies that indicate at least some massive stars that explode are living in pairs. When two stars are close to each other, one can dump matter on, or strip matter from, the other, making things more challenging to interpret.”

The paper ‘Identification of the Central Compact Object in the young supernova remnant 1E 0102.2-7219’ is published in Nature Astronomy.