Astronomers have discovered a rare type of stellar system where all the conditions for the explosion of a kilonova (an explosion accompanied by the merger of two neutron stars). Scientists note that a kilonova explosion produces huge amounts of precious metals, including gold.
According to the Russian news agency RIA Novosti, the stellar system CPD-29 2176, consisting of two stars about 11,400 light-years away from Earth, was discovered by astronomers in 2016. It is currently being studied in detail using the 1.5-meter SMARTS telescope at the Inter-American Observatory in Cerro Tololo in Chile.
Thanks to the research, scientists have been able to understand the evolution of this system. In the first phase, two giant blue stars formed a stable pair, so to speak. Then the smaller star took much of its outer atmosphere from the other. The larger star then collapsed as a result of an explosion occurring within the star. If the mass of the star's core is three times the mass of the Sun, the explosion produces a black hole, but if less, as in this case, it produces a neutron star.
The event in CPD-29 system 2176 is a weakened version of a supernova explosion. According to Noel Richardson, a researcher at Embry-Riddle Aeronautical University (USA), the lead author of the study, it is a relatively "silent death" of a distant star, thanks to which a smaller star retained its place in the system.
Evolution of the stellar system CPD-29 2176
The resulting neutron star, in turn, begins to "eat" its neighbor. Astronomers are now monitoring this very phenomenon. Having lost a significant part of its atmosphere, the companion star will also "die", turning into a neutron star. True, this process will be observed by future astronomers in about a million years.
After some time, the two neutron stars will collide again. As a result, there will be an explosion of the kilonova, which will create powerful gravitational waves and leave behind a large volume of heavy elements.
According to the authors of the study, this system, consisting of a neutron star and a "partner" star, is an "exceptionally rare" combination. Scientists estimate that there are only about ten such objects in the entire Milky Way galaxy.
All elements of the periodic table of Mendeleev were produced by stars during their "life or death." The only exception is hydrogen, which was formed in the Big Bang. The process by which stars produce elements is called nucleosynthesis. This is what gave rise to the planets, as well as life on Earth.
Astrophysicists have found that Kilonova explosions produce more than half of all matter heavier than iron. The outburst, recorded in 2017, caused atoms of heavy elements such as platinum, gold and silver to be ejected into space. The total mass of the ejected elements is 16,000 times the mass of the Earth.
Scientists suggest that it is likely that the gold we use on Earth also came from the Kilonova explosion.