[ad_1]
It is an image of Apep captured at 8 microns in the thermal infrared with the VISIR camera on the VLT telescope of the European Southern Observatory, at Mount Paranal, at Chile. The system can be seen as a binary system, with a much weaker companion north of the core of the system. This companion is not thought to play a role in sculping the extended dust plume, about 12 seconds of bow. The origin of this structure comes from the central region, supposed to contain itself a binary (the whole being a triple star). Credit: Peter Tuthill / University of Sydney / ESO
The astronomers of the University of Sydney, in collaboration with international colleagues, have discovered a unique star system in our galaxy.
Scientists believe that one of the stars – about 8000 light years from Earth – is the first known candidate in the Milky Way to produce a dangerous gamma ray burst, among the most energetic events in the world. universe, when it explodes and dies.
The system, composed of two extremely bright stars, has been dubbed Apep by the god of chaos, the Egyptian serpentine. A star is on the verge of a massive explosion of supernova.
The results, published today in Nature Astronomy, are controversial since no gamma burst has been detected in our own galaxy, the Milky Way.
Yet, in the southern constellation of Norma, nestled just under the tail of Scorpio, astronomers have discovered this star system of unique beauty.
At its heart, wrapped in a plume of dust and elegantly carved gas, is a powerful binary couple.
The two hot and bright stars, known to astronomers as the Wolf-Rayets, gravitate around each one hundred years or so, according to research conducted at the Institute of Astronomy of Sydney.
This orbital dance is embossed on a fast wind dripping stars. Using astronomical spectroscopy, astronomers measured the speed of stellar winds at a speed of up to 12 million kilometers at the time, about 1% of the speed of light.
Dr. Joe Callingham, lead author of the study, said, "We discovered this star as a special case during a survey with a radio telescope from the University of Sydney.
"We knew immediately that we had found something exceptional: the brightness across the spectrum, from the radio to the infrared, was out of reach," said Dr. Callingham, currently at the University of Ottawa. Netherlands Institute of Radioastronomy.
"When we saw the magnificent plume of dust wrap around these glowing stars, we decided to call it" Apep "- the monstrous deity of the snake and the enemy mortal of the sun-god Ra of Egyptian mythology. "
This animated gif is intended to illustrate the geometry of the structure that we saw in the Apep system. From a single image, it is more difficult to understand the 3D structure. The central binary (only: not the largest companion of the North in the triple) is illustrated by the blue star in the center. The given geometry corresponds to what is typically thought of a Wolf-Rayet collector-spoke wheel system: that is, an optically thin dust plume spread over the surface of a wind-dictated cone. in collision. The entire flow structure is wrapped in a spiral by the orbital motion of the supposed central binary. In addition, dust formation has a specific start and termination, which truncates the spiral at the outer and inner boundaries (eg giving rise to the noticeable elliptical hole). Note that there is a toy animation illustrating an overview of the structure and not a model fitted to the data describing the process of dust flow. The looping animation continues for about a half-orbit (about 60 years) with a break roughly at the present time. Note that the motion we actually recorded with VISIR in the actual data only extends over 3 years. Credit: Peter Tuthill / University of Sydney / ESO
This carved plume is what makes the system so important, said Professor Peter Tuthill, head of research group at the University of Sydney.
"When we saw the spiral tail of dust, we immediately realized that we were dealing with a rare and special type of nebula called a reel," said Professor Tuthill.
"The curved tail is formed by centrally located binary stars in orbit, which inject dust into the expanding wind, creating a pattern similar to that of a rotating turf sprinkler." Stars at the heart of the system ".
However, the data on the plume presented an enigma: the stellar winds extended 10 times faster than the dust.
"It was just amazing," said Professor Tuthill. "It was like finding a feather caught in a hurricane that drifted to the rhythm of walking."
Benjamin Pope, co-author of the University of New York, said: "The key to understanding the strange behavior of the wind lies in the rotation of the central stars.
"What we found in the Apep system is a supernova precursor that seems to spin very fast, so fast that it could be close to breaking."
The stars of Wolf-Rayet, like those who lead the plume of Apep, are known to be very massive stars at the end of life; they could explode as a supernovae at any time.
"The fast rotation gives Apep a new class – normal supernovae are already extreme events, but adding rotation to the mix can really throw fuel on the fire."
The researchers believe that this could be the recipe for a perfect stellar storm to produce a burst of gamma burst, which are the most extreme events in the universe after the Big Bang itself. Fortunately, Apep does not seem to aim the Earth because a gamma strike near it could eliminate the ozone from the atmosphere and greatly increase our exposure to the Sun's ultraviolet rays.
"In the end, we can not be certain of Apep's future," said Professor Tuthill.
"The system can slow down enough to explode like a normal supernova rather than a gamma-ray explosion, but in the meantime, it offers astronomers a seat on the edge of a magnificent and dangerous physics that we do not have. Had never been seen in our galaxy yet. "
Explore further:
Kes 75: the youngest pulsar of the Milky Way unveils the secrets of the disappearance of the star
More information:
J.R. Callingham et al., Anisotropic winds in a Wolf-Rayet binary system identify a potential precursor of gamma-ray burst, Nature Astronomy (2018). DOI: 10.1038 / s41550-018-0617-7
Source link
