White dwarf stars have been doing some weird stuff lately. There was one that was thrown through the Milky Way half-burned, and now it was discovered that a white dwarf that turned into a supernova emitted a monstrous and mysterious UV flash.
This is not your typical supernova. Whatever it is, since it doesn’t have a name yet, the phenomenon of a white dwarf exploding in ultraviolet light is so rare that this is the second time it has been observed. No one knows exactly how or why it still happens. Finding out what triggers that flash could help reveal even more dark secrets, from how the universe creates heavy metals to the cosmic acceleration believed to be caused by dark energy. Northwestern University astrophysicist Adam Miller and his team of researchers could find out.
“These are some of the most common explosions in the universe,” Miller, who recently published a study in The astrophysical journal, he said in a press release. “But what is special is this UV flash. Astronomers have searched for this for years and never found it. “
There is definitely something abnormal about this cosmic burst (now known as SN2019yvq). Type Ia (one-A) supernovae are the typical way that white dwarf binary systems go into agony, though they don’t always end what they started. Many are also superlight and the brightest supernovae known. White dwarfs made of carbon and oxygen continue to accumulate stars until they reach a limit where they end up exploding: the Chandrasekhar limit of 1.4 solar masses. It is believed to be the maximum mass a white dwarf can reach without collapsing into a neutron star or black hole.
Human eyes first saw the strange supernova the day after it exploded. Using the Zwicky Transitional Facility in California, the researchers were able to tell what happened right next to the Draco constellation, and astrophysicists then took a closer look at the X-ray and UV wavelengths at NASA’s Swift Neil Gehrels Observatory. SN2019yvq was initially classified as type Ia. It almost went through one, but the intense UV emission could not be ignored. This was not a flash that disappeared in the blink of an eye. It lasted for several days, meaning that something unfathomably hot must have been inside or at least close to the dying star. Except that white dwarfs cool as they decrease.
Such intense UV light needs something at least three to four times hotter than the sun to generate it. It is invisible to us because UV wavelengths are too short for our eyes to process, and X-rays have even shorter wavelengths. Previously, another team of researchers had found ways to determine the characteristics of superluminous supernovae using this type of light. The computer simulations that showed the event at UV wavelengths is how the explosion mechanism behind it was determined, and that method could be used to identify explosion mechanisms in other supernovae. This goes far beyond that.
“Most supernovae are not that hot, so you don’t get very intense UV radiation. Something unusual happened with this supernova to create a very hot phenomenon, “said Miller.
Miller has four hypotheses about how this could have happened. The dying white dwarf could have accumulated gas and dust in the manner of the supernova, exploding when it exceeded the limit, and the exploded star that collided with the other star in its binary system caused the UV flash. Perhaps there was super hot radioactive material in its core that heated its outer shell beyond the point of no return. There is a possibility that helium dramatically raised the star’s temperature so high that the double explosion that followed also released the UV flare. Finally, it is possible that the vast amount of UV radiation illuminated the cosmos when the two white dwarfs in the star system merged and the debris from the explosion collided.
According to Miller, what actually caused these real-life movie special effects could be revealed in about a year. Ejecta will travel farther and farther from the source until the core of the explosion is exposed. Activate the suspense.
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