Eight years later, an explosion in space is still revealing secrets about the life of stars

(ORDO NEWS) — An international team of astronomers has uncovered new information about a mysterious stellar explosion that was detected eight years ago but continues even as scientists watch it.

The results are helping astronomers better understand the life and death of massive giant stars far larger than our Sun.

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

Life 2014C

In 2014, astronomers saw a sudden bright spot in the sky – a sure sign that a star had exploded in space.

When an exploding star is discovered, astronomers around the world begin to monitor it with telescopes as the light it emits changes rapidly over time. By observing its evolution with telescopes that can see visible light as well as x-rays, radio waves, and infrared radiation, scientists can infer the physical characteristics of the system.

After doing this many times, the scientists grouped these exploding stars into categories. 2014C, as this particular event has been called, looks like a Type Ib supernova. They occur when the largest known stars in the universe die.

In fact, scientists believe that 2014C was probably originally not one, but two stars orbiting each other, one of which was larger than the other. The more massive star evolved faster and expanded. When she ran out of fuel, her core collapsed, causing a giant explosion.

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

The team set out to collect all the data on 2014C, including new data they have obtained, as well as data obtained in the course of research over the past eight years, and combine them into a coherent picture of what happened to the star.

X-rays, infrared light and radio waves showed a characteristic pattern: they either increased or decreased. At the same time, the optical light measured by the Hobby-Eberle telescope at UT Austin seemed unchanged. The radio signal 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 this strange behavior is due to a dense cloud of hydrogen around the two stars, left over from earlier periods of their lives.

When the star exploded, it produced a shock wave that traveled at about 100 million kilometers per hour in all directions. When the shock wave reached this cloud, its behavior depended on the shape of the cloud.

The simplest model assumes that this cloud is spherical and symmetrical. However, if the cloud formed a “doughnut” around two stars, that is, it would be thicker in the center, then the thick part of the ring would slow down the shock wave, appearing in optical light as slowly moving material.

At the same time, in thinner regions, the shock wave will rush forward, which will be visible in radio waves. “Imagine water hitting a rock in the middle of a river,” Dvarkadas said.

Questions remain, the scientists say, but this unevenness could explain the different shock wave speeds indicated by the different wavelengths.

The study provided valuable clues about the evolution of these stars and the mass lost from these systems, and more broadly about the life and death of these relatively enigmatic stars, the scientists said.

“Broadly speaking, how massive stars lose their mass is a big scientific question that we’ve been pursuing,” said UT Austin professor and team member Jay Craig Wheeler. “How much mass? Where is it? When was it ejected? By what physical process? Those were the mini questions we asked.”

“And 2014C turned out to be a really important one-off event that illustrates this process.”

The study was led by Benjamin Thomas of the University of Texas at Austin. Another University of Chicago researcher at work was Yerong Xu, who is now at the University of Palermo in Italy.


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