New research may improve the accuracy of "cosmic yardsticks"
Astronomers havediscovered evidence that could help solve a long standing disputeover 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 byscientists as a cosmic yard stick to chart the expansion of ouruniverse.
It is believed that theimaginatively-named supernova event G1.9+0.3 occurred roughly 110years ago. However, due to the presence of vast dust clouds of dustveiling the visible light from the cataclysmic explosion, the eventwas undetectable from Earth.
We have subsequently been successful in detecting the X-ray and radio signatures of its aftermath via advancedorbital and ground-based equipment, as these light spectra cantravel 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 alsobelongs to a rare class of explosion known as Type Ia supernovae.This family of supernovae generate a known quantity oflight when they explode, making the events an invaluable tool for astronomers.
Since we already knowto a high degree of accuracy the amount of light thrown out by thesupernovae, we are able to observe alterations in the properties ofthe light in order to chart vast cosmic distances.
So far, astronomershave failed to come together to form a single theory explaining theprocess by which the supernovae are created. Since we use the explosionsas a kind of cosmic yardstick, any inconsistency in the explosionmodel could effectively undermine our understanding of the expansionof the universe.
Prior to the studythere were two leading theories regarding Type Ia supernovae. Thefirst theory holds that Type Ia supernovae originate in a binarysystem populated by a white dwarf and a companion star, which could either take the form of a red giant, or a starsimilar to our Sun.
Over time, the white dwarf siphons material from its partner until it reaches 1.4solar masses. At this point, which is referred to as theChandrasekhar limit, the star will be doomed to end its life in a spectacular Type IaSupernova.
The second and more brutalmodel envisions the cataclysmic explosion occurring as two white dwarfs thatform a binary system smash together. This is known as the double-degenerate model.
The recent studyobserved radio and X-ray emissions from the supernova remnantcaptured by the Chandra X-ray Observatory and the Earth bound VeryLarge Array located in San Agustin, New Mexico. The team discoveredthat as time went on the radio and X-ray light grew stronger – a phenomenonthat could only occur if the explosion had resulted from a collisionbetween two white dwarf stars.
Whilst the studyprovides strong evidence for the double-degenerate model, it does notrule out the possibility that Type Ia supernovae are being created via the vampyric feeding ofa white dwarf from its companion star. Further observations of Type Iasupernovae in neighbouring galaxies in order to place the discoveryin a wider context.
A paper covering theresearch is available online through The Astrophysical Journal.