Astaunomers find the fastest star in the Milky Way: How fast does it travel?

With the help of the European Gaia satellite, astronomers have discovered four so-called "runaway" stars, two of which have record speeds, and one of them is currently the fastest moving star known to mankind: while J1235 travels at a speed of 1,694 km per second, J0927 travels at four times the galactic speed of 2,285 km per second.

Accoding to Sciencealert, such stars were first discovered in our galaxy about 20 years ago. According to scientists, such a speed will force these stars to leave the galaxy sooner or later. To date, astronomers have discovered several more such stars and continue to find new ones.

The prevailing theory today is that these stars form after the thermonuclear explosion of a white dwarf star (a class Ia supernova). Normal supernovae form after the collapse of more massive stars at the end of their evolution, while Type Ia supernovae appear after a white dwarf has accumulated a critical mass.

The white dwarf star steals that mass from its other binary partner. If it is light hydrogen, then a normal thermonuclear explosion occurs, but if the second star in the system is the same white dwarf, then it can produce mostly heavier helium, and then a double thermonuclear explosion occurs. First, a thermonuclear reaction takes place in the shell, and then a secondary explosion of the star's core occurs (this process is called Dynamically Driven Double-Degenerate Double-Detonation, or D6).

The "runaway" stars are believed to be the result of the double explosion of white dwarfs. The double thermonuclear explosion gives the pair's second star enough acceleration to eventually eject it from the galaxy. It was believed that there are about 1000 such stars in the Milky Way galaxy. Some of them may have wandered into other galaxies because their speed allows it. However, it is difficult to accurately determine the number of stars wandering in interstellar space.

The newly discovered stars, taking into account the previously discovered ones, made it possible to improve the model of the formation of such objects and further strengthen their connection with supernovae of type Ia, which in turn allowed to calculate the birth rate of such stars anew.

It was found that the rate of their appearance is well agreed with the rate of appearance of type Ia supernovae. Since supernovae of this type are clearly visible in telescopes and, moreover, they are "standard lighthouses" for determining distances in the galaxy, it is possible to calculate how many such stars there are in our galaxy, traveling at insane speeds.

Calculations show that there may be millions of such stars, just that a significant part of them are faint luminaries and have not yet been discovered. Against this background, there is a fear that one of these still undiscovered stars may suddenly appear in the path of the solar system, with very unpleasant consequences for the Earth and humanity.

The research is published in the Open Journal of Astrophysics and is available on the arXiv website.