Eight years later, a distant explosion in space is still revealing secrets about the lives of stars

Supernova investigations: Eight years later, a distant explosion in space still reveals secrets about the lives of stars

The supernova known as 2014C happened eight years ago — but scientists are still watching and learning from its fallout. The visible explosion appears faintly circled in red. Credit: Sloan Digital Sky Survey

An international group of astronomers has uncovered new evidence about a mysterious starburst that was discovered eight years ago, but continues to evolve even as scientists watch.

The findings help astronomers understand the process of how massive stars – giants much larger than our sun – live and die.

The study was published in Astrophysical Journal by a group led by the University of Texas at Austin and including scientists from the University of Chicago.

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In 2014, astronomers saw a sudden bright spot in the sky – a sure sign of a star exploding in space.

When exploding star First discovered, astronomers around the world begin to follow it with telescopes as the light it emits rapidly changes over time. By watching how it evolves using telescopes that can see visible light As well as x-rays, radio waves, and infrared lightscientists can infer the physical properties of the system.

By doing this multiple times, scientists have categorized these supernovae into categories. 2014C, as this particular event was named, looked like a so-called Type Ib supernova. It’s what happens when the largest known stars in the universe die.

In fact, scientists believe 2014C may have originally not been one star but two stars orbiting each other, one larger than the other. The more massive star developed more rapidly, expanded, sucking the outer hydrogen layer out of it. When he finally ran out of fuel, his core collapsed, causing a massive explosion.

However, observations in the first 500 days after the explosion showed that it was emitting more X-rays over time, which is unusual and is only seen in a small number of supernovae. “It suggests that the shock wave was interacting with dense matter,” said Vikram Dwarkadas, a research professor of astronomy and astrophysics at the University of Chicago.

The group set out to collect all the data for 2014C, including new data they had obtained as well as from studies over the past eight years, and adapt it into a coherent picture of what happened to the star.

X-ray emissions, infrared light and radio waves all showed the characteristic pattern of increase and decrease. Meanwhile, the optical light—measured by the Hobby Eberle Telescope at the University of Austin—appears to remain constant. The radio signals He showed that the shock wave was expanding at a very high speed, while the optical light indicated a much slower speed.

The researchers suggested that the strange behavior had something to do with the dense cloud of hydrogen around the two stars that was left early in their lives.

When the star exploded, it produced a shock wave that traveled at nearly 67 million miles per hour in all directions. When the shock wave reached this cloud, its behavior would be affected by how the cloud formed.

In the simplest model, this cloud is assumed to be spherical and symmetrical. However, if the cloud had formed a “circular cake” around the two stars – that is, thicker around the middle – the thicker part of the ring would slow down the shockwave’s velocity, shown in the optical figure. light As a slower-moving substance. Meanwhile, in thinner areas, the shock wave will rush forward, as seen in radio waves. “Think of the water hitting a rock in the middle of the river,” Doarkadas said.

The scientists said questions remain, but this disparity could explain the different speeds of Earthquake They are indicated by different wavelengths.

The scientists said the study provided valuable clues about the evolution of these stars, the mass lost from these systems, and a greater sense of the life and death of these relatively mysterious stars.

In a broad sense, the question of how huge stars Loss of its mass is the big scientific question we’ve been tracking, said J. Craig Wheeler, a professor and team member at the University of California, Austin. “How much mass? Where is it? When was it ejected? By what physical process? Those were the overall questions we were looking for.”

“And it turns out that 2014C was a really important single event that demonstrates the process.”

The study was led by Benjamin Thomas of the University of Texas at Austin. The other University of Chicago researcher on the paper is Yerong Xu, SM’20, now at the University of Palermo in Italy. For a complete list of collaborators and telescopes, see the paper.

Supernova reveals its secrets to a team of astronomers

more information:
Benjamin B. Thomas et al., Seven Years of SN 2014C: Multi-wavelength synthesis of an unusual supernova. arXiv: 2203.12747v1 [astro-ph.HE]And arxiv.org/abs/2203.12747

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