Astronomers discover supernova subset which could allow for more acurate galactic measurements

Collage of galaxies in which Type la supernovae have taken place (Image: SDSS)

NASA astronomers may have found a way to take more precise measurements of the distances between galaxies. Currently, astronomers use a certain type of supernova, known as a Type la supernova, to gauge the distances between galaxies and from this, the rate at which the universe is expanding. The reason that this particular breed of supernova is singled out for this purpose, is that when they explode, they give out a very similar amount of light.

Type la supernovae occur in binary systems, when an incredibly dense white dwarf star feeds off the stellar material of its partner until it reaches critical mass. This point is known as the Chandrasekhar limit, which occurs when the white dwarf achieves a mass the equivalent to 1.4 times that of our Sun, after which a thermonuclear explosion is imminent.

Due to the consistency in the amount of light thrown off in these explosions, they have been granted the moniker "standard candles." Measuring the dimming of the light from such a supernova by applying the inverse square law allows astronomers to accurately ascertain the distance of the event, and also the galaxy in which it took place.

However, whilst Type la supernovae are invaluable in their capacity as a cosmic yard stick, there are sometimes inconsistencies in the amount of light thrown off in the explosions. These variations, believed to be caused by some kind of environmental factor, often throw off galactic measurements.

These can in turn, make observations into the effects and therefore nature of other cosmic elements, such as dark energy, less precise. Dark energy is currently believed to be the driving force behind the continuing expansion of the universe. It also poses a significant challenge for scientists, as there is no way to observe it directly.

Instead, one must observe the effects it has on visible matter in order to discern its properties, and any discrepancies in the measurements could lead to incorrect assumptions as to the nature of dark energy.

After analyzing data collected by NASA's Galaxy Evolution Explorer (GALEX) of the past 100 observed Type la supernovae, astronomers have determined that supernovae of this type occurring in an area affiliated with the presence of hot young stars are around twice as accurate as a measuring device than other instances of Type la supernovae, and is thought to be reliable up to a distance of around 6 billion light years.

By relying on this subset of more predictable supernovae in future observations, our measurements and therefore understanding of the observable universe could be greatly refined.

A paper covering the team's findings has been accepted for publication in the online journal Science.

Source: NASA

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