The supernova is the cataclysmic explosion of a star. A thermonuclear explosion of a white dwarf supernova is thought to be the ultimate event in the life of its predecessor star.
These thermonuclear supernovae, known as type Ia supernovae, are one of the most important instruments in astronomers’ tools for measuring cosmic distances. For a normal type Ia supernova (SN Ia), which is the species used as a standardized candle for cosmology, the explosion is thought to completely untie the star.
A team of astronomers is investigating the location of the special thermonuclear supernova SN 2012Z with the Hubble Space Telescope. In a shocking revelation, they discovered that the star survived the explosion.
Not only did it survive, but the star was even brighter after the supernova than before.
First author Curtis McCully, a postdoctoral fellow at the University of California, Santa Barbara and the Las Cambres Observatory, presented the findings at a press conference at the 240th meeting of the American Astronomical Society and published them in an article in The Astrophysical Journal.
The confusing results provide new information about the origins of some of the most common but mysterious explosions in the universe. He also clarifies that there is a greater variety of white dwarf supernovae than just typical SN Ia.
The origin of thermonuclear supernovae is poorly understood, despite their vital importance to astronomy. Astronomers agree that they are destroying white dwarf stars (stars approximately the mass of the sun collected in the size of Earth).
What causes the destruction of a white dwarf?
The reason is unknown. One theory suggests that the white dwarf steals matter from another star. When the white dwarf becomes too heavy, thermonuclear reactions ignite in the nucleus, leading to a rapid explosion that destroys the star.
What could be the reason for the survival and brightness of the star?
“Iax supernovae (SNe Iax) are the most populous class of special supernovae. Based on the SN 2002cx prototype, these are backlight, low-velocity explosions compared to normal SNe Ia. In particular, there is growing evidence that SNe Iax may not completely destroy the star, but may instead leave behind a bound residue, as opposed to the complete destruction expected in SNe Ia. indicated in the study.
McCully and the team believe that the half-exploded star became brighter because it swelled to a much larger state. The supernova was not strong enough to blow all the material, so part of it fell back into what is called a bound residue. Over time, they expect the star to slowly return to its original state, only less massive and larger. Paradoxically, for white dwarfs, the smaller their mass, the larger their diameter.
“This surviving star is a bit like Obi-Wan Kenobi, who is returning as a ghost of power in Star Wars,” said co-author Andy Howell, an associate professor at the University of California, Santa Barbara and a senior scientist at the Las Cambres Observatory. “Nature tried to bring down this star, but it came back more powerful than we could have imagined. It is still the same star, but again in a different shape. It transcends death. “
Left: Color image of the galaxy NGC 1309 before Supernova 2012Z. Right: Clockwise from top right: the position of the supernova before the explosion; SN ~ 2012Z during the visit in 2013; the difference between the images before the explosion and the observations from 2016; the location of SN ~ 2012Z in the last observations in 2016. Photo: MCCULLY ET AL.
For decades, scientists have believed that type Ia supernovae explode when a white dwarf star reaches a certain size limit, called the Chandrasekhar limit, about 1.4 times the mass of the sun. This model has fallen somewhat out of favor in the last few years, as many supernovae are less massive than this one, and new theoretical ideas show that there are other things that make them explode. Astronomers were unsure if the stars had ever approached the Chandrasekhar boundary before exploding. Now the authors of the study believe that this growth to the limit is exactly what happened with SN 2012Z.
“The consequences for type Ia supernovae are profound,” McCully said. “We’ve found that supernovae can at least grow to the limit and explode. Still, the explosions are weak, at least in some cases. Now we need to understand what makes a supernova fail and become type Iax and what makes a successful type Iax.
Futuristic view:
“We encourage others to use our observations as limitations for their simulations to better understand the physical mechanisms that produce SNe Iax.” The study mentions.
Journal reference
- Curtis McCully, Surab W. J., Richard A. Scalzo, D. Andrew Howell, Ryan J. Foley, Yaotian Zen, Zheng-Wei Liu, Griffin Hosseinzade, Lars Bildsten, Adam G. Rhys, Robert P. Kirchner, GH Marion and Esau Camacho-Neves. Still brighter than before the explosion, SN 2012Z has not disappeared: Comparing observations of the Hubble Space Telescope to a decade. The Astrophysical Journal, Volume 925, Number 2. DOI: 10.3847 / 1538-4357 / ac3bbd
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