Dr. Henri Boffin, an astronomer working for the European Southern Observatory, along with colleagues, utilized the Very Large Telescope in Chile’s Atacama Desert to observe Henize 2-428, a colossal gas cloud located 4,000 light-years away from Earth. This nebula formed after a red giant star died, expelling its matter into space and transforming into a white dwarf. Their initial goal was to understand the cause behind the peculiar shape of this nebula.
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Approximately 4,000 light-years away from Earth, Henize 4-284 is a peculiarly shaped nebula. Photo: SPL.
When they looked at the central region of the nebula, they discovered two celestial bodies orbiting each other at an extremely close distance, as reported by Nature.
The two objects within the nebula are white dwarf stars. In fact, they are the heaviest known pair of white dwarfs ever discovered by humans.
To eventually explode into a supernova, white dwarf stars need to increase their mass by accumulating more matter. They can achieve this by drawing material from another star or by merging with it.
When analyzing the parameters from image data, the research team realized that they were observing an incredibly unique pair of celestial bodies. Each white dwarf star had a mass equivalent to that of the Sun, and they orbited each other in just 4.2 hours. According to Einstein’s theory of relativity, the distance between them would gradually decrease over time. As they approached each other, they would lose energy. Eventually, they would collide and merge into a single star with a mass of approximately 1.8 times that of the Sun.
Any white dwarf star with a mass greater than 1.4 times that of the Sun would not be able to cool down, as the carbon in their core would be compressed to the point where nuclear reactions would reignite. Due to the presence of nuclear reactions, at some point, the white dwarf star would explode and become a supernova. This explosion could occur in about 700 million years, and the research team determined it would belong to the Ia group, meaning it would have enough destructive power to annihilate the star into dust.
“The formation of a Type Ia supernova through the merger of two white dwarf stars is a phenomenon that has only existed in theory. The pair of white dwarf stars in the Henize 2-428 nebula is experimental evidence of this phenomenon,” explained Dr. David Jones, a researcher from the European Southern Observatory.
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Two white dwarf stars in the midst of the Henize 2-428 nebula are so close to each other that they only take 4.2 hours to complete one revolution. Photo: ESO.
Although the explosion would occur 4,000 light-years away from Earth, its brightness would still be significant enough for people on Earth to observe.
However, Philipp Podsiadlowski, an astrophysicist from the University of Oxford in the UK, does not rule out another possibility: after the merger, the two white dwarf stars would collapse into an imploding supernova.
“If the supernova collapses inward, then after a brief explosion, an incredibly dense neutron star will be born,” he explained.