Dr. Freire and his colleagues put Einstein to the test in a cosmic laboratory 7,000 light years from earth, where two exotic stars are circling each other. One, known as a white dwarf, is the cooling remnant of a much lighter star. Its companion is a pulsar, which spins 25 times every second. Though the pulsar is just 12 miles across, it weighs twice as much as the sun.
"When you have such a big mass in such a small space you have extremely high gravity," said Charles Wang, a theoretical physicist at the University of Aberdeen, Scotland, who wasn't involved in the study.
The gravity on the pulsar's surface is 300 billion times as great as the gravity on Earth. The conditions there approach the relentless, overwhelming power of a black hole, which swallows even light.
"We're testing Einstein's theory in a region where it has never been tested before," said Dr. Freire.
The pulsar and white dwarf pair emit gravitational waves and the binary star system gradually loses energy. As a result, the stars will move closer to each other and orbit faster. Einstein's theory suggests the stars' orbital periods—the time they take to go around each other—ought to shrink by about eight-millionths of a second per year.
Dr. Freire's and his colleagues used several telescopes to take precise measurements of the two-star system. Their results perfectly matched the Einstein-based prediction.Einstein's theory was published in 1916. 97 years later, using technology he could not have envisioned, a theory that made a prediction about gravity with a precision in the millionths of a second is proven true... again.
"Elegant" is not good enough a word to describe science at this level.
And, just for fun, another photo of deep space from the Hubble telescope, this one a stellar-remnant nebula in the constellation Pyxis: