Milky Way banishing stars?

Picture above is an artist's conception of a hypervelocity star.
Recently astronomers, using the MMT observatory in Arizona, discovered two stars leaving the Milky Way galaxy at speeds over 1 million mph, so fast they will never return to our galaxy! The first exiled star was discovered in 2005, two more were later found in Europe, and these two recently discovered stars brings the total amount of known exiled stars to five. These stars make up a new class of objects known as hypervelocity stars. Astronomers suspect there to be 1,000 of these stars exists in our galaxy, our galaxy containing roughly 100 billion stars.
Theoretically it is believed that these stars were thrown out of our galaxy's center millions of years ago. Each star belonging to a binary star system (two stars orbiting each other). When the binary pair come too close to the black hole in the center of our galaxy, the black hole's intense gravity pulls the stars apart, capturing one star while flinging the other out of the galaxy at great speeds. Detailed studies of our galaxy's center have found stars orbiting the black hole with very elongated, elliptical orbits, the same kind of orbits expected from the past companions of hypervelocity stars.
It is estimated that another star is thrown out of our galaxy every 100 thousand years on average. Though seeing one of these stars ejected is very unlikely, so trying to find these stars are very difficult. Astronomers must find common characteristics in the stars already discovered and search stars with these same characteristics.

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