New research may improve the accuracy of "cosmic yardsticks"

Image of supernova remnant G1.9+0.3 composed from data harvested by the Chandra X-ray Observatory(Credit: NASA/CXC/CfA/S. Chakraborti et al)

Astronomers have discovered evidence that could help solve a long standing dispute over the origin of Type Ia supernovae, by observing the youngest example of the titanic explosions located to date. The light from the rare breed of supernovae is used by scientists as a cosmic yard stick to chart the expansion of our universe.

It is believed that the imaginatively-named supernova event G1.9+0.3 occurred roughly 110 years ago. However, due to the presence of vast dust clouds of dust veiling the visible light from the cataclysmic explosion, the event was undetectable from Earth.

We have subsequently been successful in detecting the X-ray and radio signatures of its aftermath via advanced orbital and ground-based equipment, as these light spectra can travel through the choking clouds of dust and gas effectively unhindered.

G1.9+0.3 is not only significant because it is the youngest known supernova, it also belongs to a rare class of explosion known as Type Ia supernovae. This family of supernovae generate a known quantity of light when they explode, making the events an invaluable tool for astronomers.

Since we already know to a high degree of accuracy the amount of light thrown out by the supernovae, we are able to observe alterations in the properties of the light in order to chart vast cosmic distances.

So far, astronomers have failed to come together to form a single theory explaining the process by which the supernovae are created. Since we use the explosions as a kind of cosmic yardstick, any inconsistency in the explosion model could effectively undermine our understanding of the expansion of the universe.

Prior to the study there were two leading theories regarding Type Ia supernovae. The first theory holds that Type Ia supernovae originate in a binary system populated by a white dwarf and a companion star, which could either take the form of a red giant, or a star similar to our Sun.

Over time, the white dwarf siphons material from its partner until it reaches 1.4 solar masses. At this point, which is referred to as the Chandrasekhar limit, the star will be doomed to end its life in a spectacular Type Ia Supernova.

The second and more brutal model envisions the cataclysmic explosion occurring as two white dwarfs that form a binary system smash together. This is known as the double-degenerate model.

The recent study observed radio and X-ray emissions from the supernova remnant captured by the Chandra X-ray Observatory and the Earth bound Very Large Array located in San Agustin, New Mexico. The team discovered that as time went on the radio and X-ray light grew stronger – a phenomenon that could only occur if the explosion had resulted from a collision between two white dwarf stars.

Whilst the study provides strong evidence for the double-degenerate model, it does not rule out the possibility that Type Ia supernovae are being created via the vampyric feeding of a white dwarf from its companion star. Further observations of Type Ia supernovae in neighbouring galaxies in order to place the discovery in a wider context.

A paper covering the research is available online through The Astrophysical Journal.

Source: NASA

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