Wrinkles in spacetime may reveal black holes

The motions of these stars are detectable by ground-based telescopes like Gemini, and with space-based telescopes such as the Hubble Space Telescope.

Gravitational wave detectors go about detecting black holes in a completely different way, said Doug Richstone, a Laser Interferometer Space Antenna (LISA) science team member and a researcher from University of Michigan.

A predicted ripple effect
Einstein's general theory of relativity predicts that concentrations of mass or energy warp the fabric of the universe. According to his theory, changes in the shape and concentration of mass or energy will cause distortions that move out like ripples on a pond.

When a black hole swallows a neutron star or another black hole, or when two black holes merge or just orbit each other very closely, they’ll emit these ripples in spacetime, Richstone told SPACE.com.

Scientists can detect gravity waves by how they move objects in space. For example, two probes sitting stationary in space, apart from each other, will jiggle slightly when a gravity wave rolls by. This is akin to buoys at sea displaced by waves. LISA — the first dedicated space-based gravitational wave observatory and a joint venture of NASA and the European Space Agency — will be able to measure such distortions of spacetime.

“Just like you’re floating on the ocean, as waves go by, you go up and down," Richstone said. “And so the trick is to measure the separation between test masses that have been isolated from all forces except gravitational forces.”

Hunt for gravitational waves
Similar to LISA, a ground-based observatory — with installations in Hanford, Wash., and Livingston, La., and called the Laser Interferometer Gravitational-wave Observatory (LIGO) — will be used for detecting cosmic gravitational waves.

LIGO works by shining a laser light to a detector. As ripples pass by, the light beam should be slightly perturbed. The different frequencies in the waves will allow astronomers to figure out the source of a disturbance. LIGO, a collaborative effort between Caltech and MIT, began its search for cosmic waves in 2002.

“It is possible that, depending on how long it will take for LISA to get to space, that LIGO will detect a gravitational wave source first. But I think it’s just a question of which one will do it first,” Richstone said.

LISA is scheduled to launch in 2015.

“No one has detected gravitational waves yet. If LISA flies and works properly, it will detect gravitational waves from astronomical sources," Richstone said. "If it doesn’t, then Einstein’s theory of general relativity is wrong.”

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