The new discovery of six more runaway stars in the Milky Way has landed the fastest object of its kind ever discovered in the galaxy. In fact, the two stars are record holders with heliocentric radial velocities higher than any other runaway star. The star J1235 is moving at 1,694 kilometers (1,053 miles) per second; and at a staggering 2,285 kilometers (1,420 miles) per second, according to sciencealert.com, J0927

But four of the newly measured objects are so-called hyper-velocity stars that move at speeds greater than the Milky Way’s separation speed; and all four are likely the result of spectacular Type Ia supernovas—the “standard candles” by which we measure the universe, according to a team led by astrophysicist Karim El-Badri of the Harvard-Smithsonian Center for Astrophysics.

They say this allowed them to recalculate the birth rates of these stars and find that this is consistent with the estimated rate of Type Ia supernovae. Their findings are detailed in a submitted paper. Open Journal of Astrophysics and available on the arXiv preprint server.

“A substantial population of weaker, low-mass leaks may yet be waiting to be discovered,” the researchers write.

Whenever a star explodes, the power of the explosion can hurl whatever remains into space at high speeds. Hyperspeed stars are thought to be the product of a so-called dynamic double degenerate double explosion, a special type of supernova that gives the star a greater-than-normal thrust. This is a scenario that explains what happens during a Type Ia supernova.

In a binary system you have to start with a pair of white dwarfs. These are the remaining cores of low-mass stars, about eight times the mass of the Sun, that have exhausted their fusion material, ejected most of their mass, and collapsed into a dense core glowing with residual heat. Such objects are known as degenerate stars. A white dwarf has a mass limit, known as the Chandrasekhar limit, which is about 1.4 times the mass of the Sun. Above this limit, the star becomes unstable and explodes as a Type Ia supernova.

To reach this critical mass, a white dwarf would need to be in a sufficiently close binary system with another star, gravitationally pulling matter away from its companion, and have an increasing mass over time. What happens depends on the type of companion star. If a white dwarf ejects hydrogen, it results in a classical nova;

However, if the companion is a white dwarf with a significant helium surface layer, the cannibalistic star will absorb it instead. This creates a larger layer of helium on the donor star’s surface, which will quickly turn into carbon when it reaches high enough pressure and heat.