Other similar observations have been made of pairs of dense objects called neutron stars. However, because these stars can be only up to three times as massive as the sun, they don't curve space-time much more than the warping scientists see in the solar neighborhood.
Thus, studying the space-time around the Milky Way's gigantic black hole should offer an unprecedented test.
"This is the same idea in an unexplored parameter space," said Andrea Ghez, a professor of astronomy at the University of California, Los Angeles, and one of the leaders of the research team that found S0-102. "We know relativity breaks down on a small scale. We want to get as close to the event horizon as possible."
The event horizon around a black hole is the point of no return — the closest anything can come without falling in.
The stars S0-102 and S0-2 appear to get fairly close. Their orbits are so near the central black hole that the effects of space-time curvature should be clearly visible. And the presence of these two short-period stars will allow observers to measure the local space-time curvature far more accurately than one star would.
The duo also helps astronomers take into account the fact that the gravitational mass of the central black hole isn't a perfect point; there are lots of other objects, such as remnants of dead stars, in the region that can cloud the observations.