Scientists have recorded for the first time traces of the existence of radioactive molecules in space, observing one of the most unusual stars in the Milky Way, resulting from the collision of two other luminaries. Their findings were presented in the journal Nature Astronomy.
“In fact, we managed to 'open' the interior of a star that was torn apart three centuries ago, and find in it an active source of atoms of one of the rarest and shortest-lived isotopes of aluminum. The discovery of aluminum-26 in its remains will help us better understand how the chemical evolution of our Galaxy proceeds,”says Tomasz Kaminski of Harvard University (USA).
Ecumenical loss
After the Big Bang, there were only three elements in the universe - hydrogen, helium, and trace amounts of lithium. However, after 300 million years, when the first stars appeared, heavier elements began to appear, born in the course of thermonuclear reactions in the bowels of the stars.
Scientists today believe that all elements heavier than iron, including gold, uranium, and other heavy and rare earth metals, originated in large part from supernova explosions, since the temperature and pressure inside stars are too low for them to form quickly.
On the other hand, recent attempts to estimate the amount of gold and other heavy elements generated by supernovae suggest that the latter form these substances extremely slowly. This indicates that other, more exotic processes, such as collisions of neutron stars, may have been involved in their birth.
Kaminski and his colleagues discovered another source of astronomical "metals" directly related to the formation of the Earth and other planets, observing one of the most bizarre stars in the galaxy, the star CK in the constellation Chanterelle.
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It is the most ancient "new star" that was discovered and studied by professional astronomers at the end of the 17th century. By this word, scientists do not mean really new luminaries, but already existing stars, whose brightness rose sharply and then fell under the influence of some internal processes or interactions with other celestial bodies.
Unlike most other novae, CK Vulpeculae exploded in 1670 not as a result of interactions between white dwarfs and ordinary stars, but because of an even more catastrophic event - a head-on collision of two small stars.
This "cosmic accident" led to an explosion, almost equal in strength to a supernova explosion, and the birth of a new star, a small red or orange dwarf. This star was several thousand times fainter than the outburst itself, which lasted for about two years, which is why astronomers cannot find CK Vulpeculae until now.
Isotope factory
As Kaminski notes, his team was not interested in the star itself, but in the glowing nebula that emerged after the explosion. Inside it, as scientists have long suspected, there must be a huge number of rare isotopes of various elements that arose at the moment of collision of the luminaries, when the temperatures and pressures inside their matter reached record highs.
Of particular interest to scientists is aluminum-26, one of the rarest isotopes of this metal on Earth that does not exist in nature today. This type of metal, according to physicists, is formed only during supernova explosions and in the bowels of super-hot "shaggy" luminaries, the so-called Wolf-Rayet stars, and it very quickly turns into stable magnesium-26 for several million years after its birth.
The primary matter of the solar system, as shown by the proportion of magnesium isotopes in the matter of ancient meteorites, contained large amounts of aluminum-26. This has put before scientists one of the main mysteries in the history of the formation of the Earth and other planets - where did this isotope come from, whether supernovae were its only source and where the Sun could have been born.
Kaminsky and his colleagues managed to partially solve this mystery by observing the gas and dust "shroud" of CK Vulpeculae using the APEX microwave telescope, installed on the Chilean high plateau of Chahnantor. Like its "big sister", the ALMA Observatory, it can track the movement of even the coldest and smallest molecules in such dense accumulations of gas and dust.
As it turned out, inside the nebula surrounding CK Vulpeculae, there is a fairly large amount of this metal in the form of molecules containing one atom of aluminum-26 and fluorine. Their total mass, according to astrophysicists, was quite large - about 3.4 quintillion tons, which is equivalent to a quarter of Pluto's mass.
They, as Kaminsky notes, were the first radioactive molecules that scientists managed to find in outer space, and the first evidence that not all aluminum-26 is produced by supernovae and hot stars. Further observations of this unusual star, scientists hope, will help to understand what role such collisions of stars play in the chemical evolution of the Galaxy and in the formation of potentially habitable planets.