Dying stars tend to go out with a bang, producing spectacular flashes of light visible in our night skies. Here, NASA photographed a distant white dwarf star erupting in what is known as a “classical nova”. White dwarfs represent the very last stage in a dying star’s lifecycle and they are the core remnants of a star that has run out of fuel. According to NASA, white dwarfs are generally born from low to medium mass stars like our Sun.
And sometimes, white dwarfs will spontaneously erupt into so-called classical nova like the one in NASA’s photo.
NASA said: “This object became a sensation in the astronomical community when a team of researchers pointed at it with our Chandra X-ray Observatory telescope in 1901, noting that it suddenly appeared as one of the brightest stars in the sky for a few days, before gradually fading away in brightness.
“Today, astronomers cite it as an example of a ‘classical nova’, an outburst produced by a thermonuclear explosion on the surface of a white dwarf star, the dense remnant of a Sun-like star.”
The object in question is GK Persei or Nova Persei 1901 – a bright nova that occurred in 1901.
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The cosmic blast was first discovered in February 1091 by a Scottish clergyman named Thomas David Anderson.
The blast was found in the Constellation Perseus and until 1918, was the brightest nova to light up the skies over Earth.
But what caused the white dwarf star to so spectacularly combust in the first place?
The team behind NASA’s Chandra telescope explained: “A nova can occur if the strong gravity of a white dwarf pulls material from its orbiting companion star.
“If enough material, mostly in the form of hydrogen gas, accumulates on the surface of the white dwarf, nuclear fusion reactions can occur and intensify, culminating into a cosmic-sized hydrogen bomb blast.
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“The outer layers of the white dwarf are blown away, producing a nova outburst that can be observed for a period of months to years as the material expands into space.”
In some ways, scientists consider classical novae to be the smaller cousins of supernova explosions.
Supernovas are the considerably bigger eruptions of entire stars, which are momentarily so bright they can outshine their host galaxy.
In both cases, however, both novae produced powerful shockwaves that ripple out through space at hypersonic speeds.
The blast wave from the nova was estimated to be travelling at about 700,000mph.
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NASA’s Chandra telescope first observed GK Persei in 2000, followed by more observations in 2013.
The 13 years in-between observations gave NASA enough time to observe how the nova has changed.
The Chandra team said: “One intriguing discovery illustrates how the study of nova remnants can provide important clues about the environment of the explosion.
“The X-ray luminosity of the GK Persei remnant decreased by about 40 percent over the 13 years between the Chandra observations, whereas the temperature of the gas in the remnant has essentially remained constant, at about one million degrees Celsius.”