The matter accreting onto the black hole is unlikely to fall directly in, but will have some angular momentum around the black hole, which will cause the matter to collect into an accretion disc. Quasars may also be ignited or re-ignited when normal galaxies merge and the black hole is infused with a fresh source of matter. In fact, it has been suggested that a quasar could form when the Andromeda Galaxy collides with the Milky Way galaxy in approximately 3–5 billion years.