News in Science

Nova fireworks 1500 light years away

StarStuff image of the week It looks like classic New Year's Eve fireworks, but this spectacular display is the GK Persei nova, in the constellation Perseus.

A nova involves the explosion of material on the surface of a white dwarf star, but unlike the more powerful supernovae (in which the star is destroyed) the explosion can repeat over and over again.

Located some 1500 light years from Earth, GK Persei was first seen in 1901 and was the brightest nova in the sky until 1918 (when Nova Aquilae appeared.)

Since then, GK Persei has displayed regular outbursts of brightness every three years or so, usually lasting about two months per episode.

This new image of GK Persei combines data from multiple telescopes.

Hot gas expanding out from the nova were picked up in X-rays detected by NASA's Chandra telescope, which are displayed as blue.

Clumps of material being ejected in the nova explosion were revealed by optical data taken by NASA's Hubble Space Telescope and are shown in yellow.

Radio wavelengths collected by the National Science Foundation's Very Large Array radio telescope are shown in pink and indicate emissions from electrons that had been accelerated to high energies by the nova shock wave.

The nature of the point-like source on the lower left of the image is unknown.

Chandra first observed GK Persei in February 2000 and then again in November 2013, providing astronomers with enough time to notice important differences in the nova's X-ray emission and its properties.

Over the 13 years, debris from the remnant expanded at a speed of about 1,127,000 kilometres per hour, with the blast wave moving about 145 billion kilometres during that period.

One intriguing discovery is that the X-ray luminosity of the GK Persei remnant decreased by about 40 per cent over the 13 years between the Chandra observations, while the temperature of the gas has remained constant at about a million degrees Celsius.

As the shock wave expanded and heated an increasing amount of matter, the temperature behind the wave of energy should have decreased.

The observed fading and constant temperature suggests that there was very little gas in the space around the nova, giving scientists clues about the stellar neighbourhood in which GK Persei resides.

Hosted by Stuart Gary, StarStuff takes us on a weekly journey across the universe. StarStuff reports on the latest news and discoveries in science, with a special focus on astronomy, space sciences and cosmology.



