In other cases, another member of the system will form a second white dwarf. If gravitation instability these two objects bring together, their collision makes a single object with a much higher mass. This will also restart the merger, which leads to an explosion.
We have found evidence for both events that take place. However, there are some questions about whether they happen often enough to explain the frequency of type IA Supernovae that we see. Both mechanisms require stars of sufficient mass to have a job at a reasonably narrow distance to have a massive transfer or a collision. Astronomers have therefore considered other ways to blow up a white dwarf.
The most promising option seems to be a double detonation. This can also be the transfer of some helium-rich material from another companion, but it can also occur if the white dwarf ends with a non-not-stuff left on the surface. Regardless of how it ends there, the helium can begin to melt if it is enough, or simply if the movement causes a sufficiently high local density in one region. However, it happens as soon as the merger starts, the entire surface of the white dwarf will follow quickly, creating inflammatory number one.
That in turn will create compression in the carbon oxyte section of the white dwarf, which it pushes past the density needed to merge with it. Again, the initiation of merger heats and compresses nearby material, creating a chain reaction that causes widespread merger in the white dwarf, it blows into pieces as part of explosion two.
A shell game
The most important thing about this is that it makes the explosion of white dwarfs possible before reaching a mass that is sufficient enough to activate the merger of their carbon and oxygen. Instead, it may happen at any time that enough helium collects on their surface. An event with double detonation would also be very difficult to detect, because the explosions would take place quickly and the environment in the immediate vicinity of a type of ia supernova complex and difficult to resolve.
