In December 2019 researchers at the Palomar Observatory near San Diego, found a supernova explosion using the Zwicky Transient Facility (funded by the National Science Foundation, NSF). Within hours, the astrophysicists with the help of NASA’s Neil Gehrels Swift Observatory observed the event in ultraviolet and x-ray wavelengths and classified it as type 1a supernova. Supernovae are a common phenomenon, but this particular explosion had something that seemed to be peculiar. It was a type 1a supernova, which occurs when a white dwarf explodes. The event named as SN2019yvq occurred in a relatively nearby galaxy NGC 4441 located 140 million light-years from Earth, very close to the tail of the dragon-shaped Draco constellation. What made it so special is that in the days after the explosion it displayed an ultraviolet flash of lights, which is observed very rarely.
The research was led by Adam Miller, an astrophysicist at Northwestern University. A paper was published in the astrophysical journal on July 23, 2020. It is the second time UV flash is observed with a supernova explosion. The event can tell us many things about long-standing mysteries, including what causes white dwarfs to explode, how dark energy accelerates the cosmos and how the universe creates heavy metals, such as iron.
“These are some of the most common explosions in the universe, but the specialty of this explosion is the UV flash. Astronomers have been researching this for years and have never found it. To our knowledge, this is actually only the second time a UV flash has been seen with a type Ia supernova,” said Adam Miller who led the study. “The UV flash is telling us something very specific about how this white dwarf exploded. As time passes, the exploded material moves farther away from the source. As that material thins, we can see deeper and deeper. After a year, the material will be so thin that we will see all the way into the center of the explosion,” Miller said.
White dwarfs are stars in the final phase of stellar life, having exhausted all their nuclear sources of energy, as well as their capacity to release gravitational energy by contraction. They have an average density in the range of 10^5 – 10^6 grams per cubic centimetre. They become cooler and cooler as they age by radiating their thermal energy. The ultraviolet flash of light can be observed only in association with something that is very hot, even hotter than the sun. “Most supernovae are not that hot, so you don’t get the very intense UV radiation. Something unusual happened with this supernova to create a very hot phenomenon,” the researcher says. And that is the reason that makes this particular explosion something special. Researchers believe that understanding of this event can help in solving the mysteries related to the explosion of white dwarfs. Currently, there are multiple hypotheses on how white dwarfs will explode with a UV flash of light. Researchers believe that within a year, with further studies, they can conclude which, among the hypothesis is true.
Further insights from the study:
Once we know about how type 1a supernova occurs that can help in answering many questions about planet formations and dark energy. The core of the Earth and other rocky planets are made up of iron and most of the iron in the universe is created by type 1a supernova. Hence a better understanding of the phenomenon can tell us many things about our own planet.
White dwarfs have a crucial role in the understanding of dark energy. Physicists predict that all the white dwarfs will have the same brightness when they explode. This factor is used to calculate exactly how far the explosion lie from earth. “Most galaxies are actually moving away from us. If there are type Ia supernovae exploding in very far away galaxies, their distances and velocities can be inferred from how bright those supernovae apear to us on Earth,” explained Caltech graduate student Yuhan Yao, a co-author on this paper. “Astronomers have thus found that the Universe is expanding in an ever faster rate, and the most popular explanation is that two thirds of the Universe is made up of the mysterious dark energy.”
Miller says, “At the moment, when measuring distances, we treat all of these explosions as the same, yet we have good reason to believe that there are multiple explosion mechanisms. If we can determine the exact explosion mechanism, we think we can better separate the supernovae and make more precise distance measurements.”
We can all hope that with the better understanding of the explosion of white dwarfs, we can finally shed some light into the mysteries that we are constantly trying to unveil.
References: caltech.edu news.northwestern.edu
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