The star that survived a supernova

The star who survived a supernova

Galaxy NGC 1309. Credit: NASA, ESA, Hubble Heritage Team (STSCI/AURA), and A.Ress (JHU/STSCI)

A supernova is a catastrophic explosion of a star. Thermonuclear supernovae, in particular, refer to the complete destruction of a white dwarf star, leaving nothing behind. At least that’s what the models and observations suggest.

So when a team of astronomers went to look at a strange thermonuclear site Supernova SN 2012Z with the Hubble Space Telescope, were shocked to discover that the star had survived the explosion. Not only did it survive, but the star was even brighter after the supernova than it had been before.

First author Curtis McCauley, a postdoctoral researcher at the University of California, Santa Barbara and Las Cumbres observatory, published these findings in an article in Astrophysical Journal He presented it at a press conference at the 240th meeting of the American Astronomical Society. The tantalizing results give us new information about the origins of some of the most common, but mysterious, explosions in the universe.

These thermonuclear supernovae, also called Type Ia supernovae, are some of the most important tools in astronomers’ toolkits for measuring cosmic distances. Beginning in 1998, observations of these explosions revealed that the universe was expanding at an ever-accelerating rate. This is believed to be due to dark energyHis discovery won the Nobel Prize in Physics in 2011.

Despite their vital importance to astronomy, the origins of thermonuclear supernovae are poorly understood. Astronomers agree that it is the destruction of white dwarf stars – stars roughly the mass of the Sun the size of the Earth. What causes stars to explode is unknown. One theory is that the white dwarf steals matter from A buddy star. When a white dwarf becomes too heavy, thermonuclear reactions in the core ignite and lead to a rapid explosion that destroys the star.

SN 2012Z was a peculiar type of thermonuclear explosion, sometimes called a Type Iax supernova. They are weaker and weaker cousins ​​to the more traditional type I. Because the eruptions are less powerful and slower, some scientists have hypothesized that they were failed Type Ia supernovae. New observations confirm this hypothesis.

The star that survived a supernova

Left: Color image of the Galaxy NGC 1309 before the 2012Z Supernova. right: clockwise from top right: position of the supernova explosion; SN~2012Z during 2013 visit; The difference between the pre-blast photos and the 2016 observations; SN~2012Z site in recent notes in 2016. Credit: McCully et al

In 2012, supernova 2012Z was discovered in the neighboring spiral galaxy NGC 1309, which has been studied in depth and captured in numerous Hubble images over the years leading up to 2012Z. The Hubble images were taken in 2013 in a concerted effort to determine which star in the old images corresponded to the one that exploded. The analysis of this data in 2014 was successful – scientists were able to determine the star in the exact location of the 2012Z supernova. This was the first time that the progenitor star of a white dwarf supernova had been identified.

“We were expecting to see one of two things when we got the latest Hubble data,” McCauley said. “Either the star has completely disappeared, or it may still be there, which means that the star we saw in the pre-burst images was not the one that exploded. No one expected to see a brighter star. That was a real mystery.”

McCauley and the team believe that the half-exploded star has become much brighter because it has swelled to a much larger state. The supernova wasn’t strong enough to blow all the material out, so some of it fell back into what’s called a binding remnant. Over time, they expect the star will slowly return to its initial state, only smaller and larger. Paradoxically, for white dwarf stars, the lower their mass, the greater their diameter.

“This surviving star looks a bit like the return of Obi-Wan Kenobi as a force ghost in Star Wars,” said co-author Andy Howell, associate professor at the University of California, Santa Barbara and chief scientist at the Las Cumbres Observatory. “Nature tried to hit this star, but it came back stronger than we could have imagined. It’s still the same star, but it’s back in a different shape. It’s past death.”

For decades, scientists have believed that Type Ia supernovae explode when a white dwarf star reaches a certain limit in size, called the Chandrasekhar limit, about 1.4 times the mass of the Sun. This model has become somewhat unfavorable in the past few years, as many supernovae have been found to be less massive than this, and new theoretical ideas have suggested that there are other things causing them to explode. Astronomers weren’t sure if the stars had ever approached the Chandrasekhar limit before the explosion. The study authors now believe that this maximal growth is exactly what happened to SN 2012Z.

“The implications for Type Ia supernovae are profound,” McCauley says. “We found it supernovae At least it can grow to the maximum and explode. But the bangs are weak, at least for a while. Now we need to understand what makes a supernova fail and become a type Iax, and what makes one successful as a type Ia.”

Image: Hubble captures the torn remains of a cosmic explosion

more information:
Curtis McCully et al, still brighter than before the explosion, SN 2012Z not gone: comparing Hubble Space Telescope observations to separate decades, Astrophysical Journal (2022). DOI: 10.3847 / 1538-4357 / ac3bbd

the quote: The Star Who Survived a Supernova (2022, June 23) Retrieved June 23, 2022 from

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