Press Releases

DATE2021.06.09 #Press Releases

A rogue in the “Cosmic Standard Candle”?


-The relic of the densest white dwarf has been detected in the remnant of its supernova.-


Overview of the press release

The central density of a white dwarf, immediately before exploding as a so-called Type Ia supernova, has been measured for the first time. The international collaboration behind this new result was led by Yuken Ohshiro, a second year masters student at the University of Tokyo’s Graduate School of Science, working with Professor Hiroya Yamaguchi (ISAS). The measurement was made from observations of the remnant of the supernova explosion, 3C 397, using the astronomical satellite XMM-Newton that was launched by the European Space Agency (ESA) in 1999.
The key that led to this achievement is the first-ever detection of neutron-rich isotopes, including 50Ti (titanium 50) and 54Cr (chromium 54), in the supernova remnant or its debris. Isotopes are atoms of chemical elements with differing numbers of neutrons (charge-less subatomic particles) in their nucleus. These detected isotopes are produced more efficiently the higher the central density of the exploding white dwarf. Using this relationship, the team revealed that the central density of 3C 397’s progenitor was about three times higher than that of a typical Type Ia supernova progenitor. This discovery adds to the mounting evidence for diversity in Type Ia supernovae, which are used in cosmology as distance indicators through the Universe.
Better understanding of their diversity will improve the reliability of the distance indicators, enabling a more accurate determination of the history of Universe expansion. The result by the team also provides a clue to the origin of the neutron-rich isotopes that are observed in carbonaceous chondrite meteorites that are thought to be generated during the formation of the Solar System.
This research has been reported in the Astrophysical Journal of Letters, published on June 4, 2021.


Left: X-ray image of the supernova remnant 3C 397. Red indicates the spatial distribution of iron, green indicates the spatial distribution of silicon, while blue is the relative abundance of chromium compared to iron. A region rich in chromium (dark blue) can be seen in the southern part of the remnant.

Right: X-ray spectrum of material within the white circle shown in the left-hand figure. Titanium, chromium, manganese and nickel were detected in addition to iron, which is the main element formed during a Type Ia supernova (credit:ISAS/JAXA, Ohshiro et al.).


To read the full press release, please visit the website of the Institute of Space and Astronautical Science (ISAS), JAXA.



Publication details


Astrophysical Journal Letters

Discovery of a Highly Neutronized Ejecta Clump in the Type Ia Supernova Remnant 3C 397
Yuken Ohshiro et al.