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Saturday, September 8, 2012

‘Cry' of a ragged Star messenger New Era for Testing Relativity


Last year, astronomers discovered an inactive black hole in a distant galaxy that explodes after grate and consuming a passing star. Identified Researchers now have a distinctive X-ray signal in the days Observed Following The explosion that comes from matter on the edge of falling into the black hole.

This tell-tale signal, called a quasi-periodic oscillation or QPO,
is a characteristic feature of the accretion disks surrounds That Often The Most compact objects in the universe - white dwarf stars, neutron stars and black holes. QPOs Have Been Seen in Many stellar-mass black holes, and there is tantalizing evidence for them in a few black holes middleweight that May have masses between 100 and 100.000 times the sun's.

Until the new finding, had been detected QPOs around only one supermassive black hole - the type Containing millions of solar masses and located at the centers of galaxies. That object is the Sifter-type galaxy REJ 1034 +396, at a distance of Which 576 million light-years relativamente lies nearby.

"This discovery extends our reach to the innermost edge of a black hole located billions of light-years away, which is really amazing. This gives us an opportunity to explore the nature of black holes and test Einstein's relativity at a Time When the universe was very different than it is today, "said Rubens Reis, an Einstein Postdoctoral Fellow at the University of Michigan in Ann Arbor. That Reis led the team uncovered the QPO signal using data from the orbiting Suzuki and XMM-Newton X-ray telescopes, to finding Described in a paper published today in Science Express.

The X-ray source Swift J1644 +57 Known as - after its astronomical coordinates in the constellation Draco - was discovered on March 28, 2011, by NASA's Swift satellite. It was originally assumed to be a more common type of outburst called a gamma-ray burst, but its gradual fade-out had been matched that nothing seen before. Astronomers soon converged on the notion That They Were seeing what was the aftermath of a truly extraordinary event - the awakening of a distant galaxy's dormant black hole as it shredded and gobbled up a passing star. The galaxy is so far away from the event that light had to travel 3.9 billion years before reaching Earth.

The star experienced intense tides as it reached its closest point to the black hole and was torn apart quickly. Some of its gas fell toward the black hole and formed a disk around it. The innermost part of this disk was heated to temperatures of rapidly millions of degrees, hot enough to emit X-rays. At the same time, through still not fully Understood Processes, oppositely directed jets perpendicular to the disk Formed near the black hole. These jets blasted outward at velocities matter Greater than 90 percent the speed of light along the black hole's spin axis. One of these jets happened to point straight just at Earth.

Nine days after the outburst, Reis, Strohmayer and Their colleagues Observed Swift J1644 +57 using Suzuki, an X-ray satellite operated by the Japan Aerospace Exploration Agency with NASA participation. About ten days later, then They Began to longer monitoring campaign using the European Space Agency's XMM-Newton observatory.

"Because matter in the jet was moving so fast and was angled nearly into our line of sight, the effects of relativity boosted its X-ray signal enough That We Could catch the QPO, Which Otherwise Would Be Difficult to detect at so great a distance, "said Tod Strohmayer, an astrophysicist and co-author of the study at NASA's Goddard Space Flight Center in Greenbelt, Md.

As hot gas in the innermost disk spirals toward a black hole, astronomers point it Reaches to refer to as the innermost stable orbit round (ISCO). Any closer to the black hole and plunges into the gas rapidly event horizon, the point of no return. The inward spiraling gas tends to pile up around the ISCO, where it becomes tremendously heated and radiates a flood of X-rays. The brightness of These X-rays varies in a pattern repeats that interval at a nearly regular basis, creating the QPO signal.

The data show That Swift J1644 +57' s QPO cycled every 3.5 minutes, Which places its source region Between 2.2 and 5.8 million miles (4 million km to 9.3) from the center of the black hole, the exact distance Depending on how fast the black hole is rotating. To put this in perspective, the maximum distance is only about 6 times the diameter of our sun. The distance from the QPO region to the event horizon depends on rotation speed Also, but for a black hole spinning at the maximum rate Allows theory, the horizon is just inside the ISCO.

"QPOs send us information from the very brim of the black hole, where the effects which is of relativity Become Most Extreme," Reis said. "The Ability to gain insight into These Processes Such a vast distance over is a truly beautiful and holds great promise result."

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