Bombs about to "explode" in the Milky Way
In the movie Speed, a bomb placed on a bus runs the risk of exploding if the speed of the bus is reduced too much. Interestingly, the plot of this action movie has a cosmic equivalent. As determined by a team of astronomers at the Harvard-Smithsonian Center for Astrophysics, some old stars of the Milky Way that are currently spinning at high speed are authentic "time bombs" that could explode as supernovas when they brake.
"We have not yet found any of these" time bombs "in the Milky Way, but our study suggests that until now we have been looking for the wrong signals," explains Rosanne Di Stefano, co-author of the research. Specifically, Di Stefano and his colleagues study a type of supernova called "Ia", which occurs when a compact white dwarf is destabilized. As they explain in the latest issue of The Astrophysical Journal Letters, when a white dwarf gains mass accelerates its turn and if it moves at sufficient speed can cross the barrier of 1.4 solar masses becomes a massive Chandrasekhar type star . However, if you stop stealing matter, the white dwarf gradually decreases its speed and, in the end, the spin is not enough to counteract gravity, leading to a type Ia supernova.
There are two possibilities that would lead to a white dwarf exploding as type Ia supernova. Either accumulate gas from a donor star, or collide with another white dwarf. Astronomers opt for the first scenario.
It is estimated that in the galaxy there are three type Ia supernovae every thousand years. If a supermassive white dwarf takes millions of years to slow down and explode, the calculations suggest that there should be dozens of systems ready to explode a few thousand light years from Earth. Now, the challenge for astronomers is to find them. To do this, as Di Stefano has pointed out, one must find small amounts of hydrogen and helium near the explosion of the supernova, measurements that until now were not made.