NASA provides 3D recreation of supernova remnant Crab Nebula
Supernovas come in various shapes and sizes but are widely regarded as the Universe’s biggest fireworks. Astronomers originally classified these as either Type I or Type II supernovas although today we know there are many more types with their own quirks. One such classification is a Type Ia supernova, which involves a white dwarf – the hot core of a star that has shed its outer layers – being ripped apart by a runaway thermonuclear reaction caused by the star merging with or siphoning too much material from a nearby companion.
Until recently, the remnant of a Type Ia blast was thought to have been found near the heart of the Milky Way – a supermassive black hole dubbed Sagittarius A* (read: A-star).
Astronomers have dubbed this object Sagittarius A East (Sgr East A).
But data from NASA’s Chandra space telescope has challenged this classification, instead suggesting astronomers have stumbled upon something much rarer.
Instead of being torn apart by a fast thermonuclear reaction, this white dwarf was destroyed by some unknown process.
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Astronomers from the US, China and the Netherlands believe they have found evidence of a Type Iax supernova.
These types do not always lead to the star’s death and according to a 2014 study by the Space Telescope Science Institute (STScI), they may even leave a “zombie star” behind.
One theory suggests Type Iax supernovas are caused by thermonuclear reactions that travel much more slowly.
The resulting explosions are consequently much weaker and can leave part of the star behind.
In other galaxies, these supernovas are about one third as frequent as Type Ia supernovas.
But what is truly incredible about the new discovery, is we have never seen evidence of such a supernova in our home galaxy.
Ping Zhou of Nanjing University said: “While we’ve found Type Iax supernovae in other galaxies, we haven’t identified evidence for one in the Milky Way until now.
“This discovery is important for getting a handle of the myriad ways white dwarfs explode.”
The explosive deaths of white dwarfs are an important source of heavy elements throughout the cosmos.
When they erupt, they shed iron, nickel and chromium out into space, effectively seeding space with the elements from which planets and life is born.
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Supernova: Simulation shows elements in exploding star
Like a colossal, nuclear furnace, stars are the only place where these elements can form.
Study co-author Shing-Chi Leung of Caltech in Pasadena, said: “This result shows us the diversity of types and causes of white dwarf explosions, and the different ways that they make these essential elements.
“If we’re right about the identity of this supernova’s remains, it would be the nearest known example to Earth.”
When astrophysicist Carl Sagan said “we’re made of star stuff” he was being literal.
In his groundbreaking 1980 series Cosmos, he said: “The formation of the solar system may have been triggered by a nearby supernova explosion.
“After the Sun turned on, it’s ultraviolet light poured into our atmosphere, it warmth generated lighting, and these energy sources sparked the origin of life.”
Because of how close Sgr A East sits to Sagittarius A*, it likely crosses paths with a disk of stellar material orbiting the black hole.
The team using Chandra’s data was able to spot the object over a 35-day period by detecting unusual X-ray signatures from this region of the Milky Way.
The results are supported by computer simulations predicting a white dwarf ripped apart by a slow-moving thermonuclear reaction.
Zhiyuan Li of Nanjing University said: “This supernova remnant is in the background of many Chandra images of our galaxy’s supermassive black hole taken over the last 20 years.
“We finally may have worked out what this object is and how it came to be.”
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