A duo of dancing stars

Small stars like our sun die with great beauty, surrounded by beautiful shells of multicolored gases that were once their outer layers – leaving only their relic cores as silent testimonies to the universe that they once existed. Our sun, like other small stars, initially becomes a bloated star red giant which will swell to the dire point that its flames will engulf the inner planets Mercury, Venus, and possibly Earth. It will then wither to a tiny, dense white dwarf–its former core. In March 2020, an international team led by astronomers from the University of Warwick (UK) reported that they had discovered a strange phenomenon involving a tightly dancing duo of these dead stars. The scientists discovered a massive white dwarf Star with a strange carbon-rich atmosphere that could really be two white dwarves who fused together as they performed their bizarres dance of death in the space between the stars – narrowly escaping explosive destruction.

The astronomers discovered something unusual ultramassive white dwarf is about 450 light-years from Earth with an atmospheric composition that had never been seen before. This important observation marked the first time that a fused dance duo dated white dwarves had been discovered by astronomers, who used its atmospheric composition as a clue to solving the mystery of its true identity.

The discovery, published in the March 2, 2020 issue of the journal natural astronomycould shed new light on the ongoing question of how massive white dwarf develop stars and the number of supernovae that live in our barred spiral galaxy of the Milky Way.

That ultramassive white dwarf, called WD J0551+4135was identified in a review of data derived from European Space Agency (ESA) Gaia Telescope. The astronomers tracked their discovery with spectroscopy obtained with the William Herschel Telescope. That’s what the scientists focused on white dwarves identified as particularly massive – an achievement made possible by the Gaia mission. By analyzing the light emitted by the strange star, the astronomers were able to determine the chemical composition of its atmosphere and found that it contained an unusually high level of carbon.

lead author dr Mark Hollands of the University of Warwick’s Department of Physics stated on March 2, 2020 University of Warwick press release that “this star was something we had never seen before. You might expect to see an outer layer of hydrogen, sometimes mixed with helium, or just a mixture of helium and carbon. You don’t expect to see this combination of hydrogen and carbon at the same time since there should be a thick layer of helium in between that forbids that.

Most white dwarves are relatively light, weighing about 0.6 times the mass of our Sun. However, WD J0551+4135 weighs an impressive 1.14 times the mass of the Sun, which is almost twice the average mass of others white dwarves. Though more massive than our sun, it’s squeezed into a tiny dense sphere just two-thirds the diameter of Earth.

In order to solve the intriguing mystery, the astronomers-detectives decided to uncover the true origins of the star. The age of WD J0551+4135 also gave them an important clue. Older stars orbit our Milky Way much faster than younger ones, and that’s strange white dwarf buzzed around our galaxy faster than 99% of the others nearby white dwarves at the same cooling age. That means this dead star is much older than it looks.

dr Hollands further stated on March 2, 2020 University of Warwick press release that “we have a composition that we cannot explain by normal stellar evolution, a mass twice the average for a white dwarf, and a kinematic age older than that derived from cooling. We’re pretty sure how a star makes you white dwarf and it shouldn’t. You can only explain it if it came about through a fusion of two white dwarves.”

The death of a small sun-like star

white dwarves are all that remains of stars like our own sun after they have burned all of their necessary supply of nuclear fusion fuel. At this fatal point, the dying little star has ejected its outer layers of gas into space. A little star big final contrasts with the noisy and explosive decline of more massive stars dying in violent and catastrophic supernova explosions. Small stars like our sun “pass gently into this good night” and perish with great beauty and relative peace. In fact, their lovely multicolored gaseous envelopes have inspired astronomers to dub them the “Butterflies of the Universe” in homage to their celestial beauty.

Lonely little stars like our sun gently perish. However, when there is another standout actor in the drama, dire complications develop. When a small star is in a binary star system with another star, a wild party inevitably ensues. When the first of the duo “dies”, it leaves behind its density white dwarf Core behind it, the star corpse will gravitationally suck material from its surviving companion star – and victim. As a vampire-like Dwarf continues to steal more and more material from its hapless companion, it will finally ingest enough material to attain enough mass to “go critical”. At this point is the white dwarf pays for his crime and explodes – just like the big ones. This explosion is denoted as a Type Ia supernovaand it differs from that Core collapse type II supernovae experienced from more massive stars.

The suggestion that WD J0551+4135 is really an object created as a result of the fusion of a duo white dwarves is based on a related but not identical theory of origin. In this case, when one of the two stars expanded into a swell at the end of its life red giantit engulfed its companion star and pulled its orbit closer and closer as the first star withered into its white dwarf Stage. An encore then occurred as the other star was bloated red giant. Over the course of billions of years, gravitational wave emission continued to shrink the orbit, to the point where the waltz star duo merged into a single object.

The dancers and their dance

Although white dwarf Mergers involving the unusual have been predicted WD J0551+4135 is stranger than expected. This is because most mergers in our Milky Way take place between stars of different masses, while this strange merger likely happened between a duo of similar-sized stars. There is also a limit to the size of the resulting single white dwarf be cam. This is because when the resulting stellar corpse weighs more than 1.4 times the mass of the Sun, it “goes critical” and blasts itself into pieces Type Ia supernova Explosion. However, it’s possible that such deadly stellar explosions could be triggered at slightly lower masses, and so this is odd white dwarf is particularly useful because it shows how massive a white dwarf got and still “live” to tell the story.

Because the merger restarts the star’s cooling process, astronomers have had a hard time calculating the star’s true age. The stellar corpse likely merged about 1.3 billion years ago — but the duo of original dead stars may have existed many billions of years before this event.

WD J0551+4135 is important because it is one of only a few merged white dwarves to be identified – and it is the only one that has so far been identified from its composition.

dr Hollands stated on March 2, 2020 University of Warwick press release that “There are not that many white dwarves so massive, although there’s more than you’d expect, suggesting some of them probably arose from mergers.”

“In the future we may be able to use a technique called Astroseismology to learn about white dwarf Core composition from its stellar pulsations, which would be an independent method confirming that this star formed from a merger. Perhaps the most exciting aspect of this star is that it almost failed to explode as a supranova – these gigantic explosions are really important for mapping the structure of the Universe because they can be detected at very great distances. However, a lot of uncertainty remains about what kind of star systems make it to the supernova phase,” he added.

“As strange as it may sound, measuring the properties of these ‘failed’ supernovas and future doubles tells us a lot about the pathways to thermonuclear self-annihilation,” commented Dr. Holland’s further.

This research is published in the March 2, 2020 issue of the journal natural astronomy under the title A Ultramassive white dwarf with a mixed hydrogen-carbon atmosphere as a probable fusion remnant.

Thanks to Judith E Braffman-Miller | #duo #dancing #stars