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NASA Scientists Identify Smallest Known Black Hole

With a new technique, two NASA scientists have determined the lightest known black hole. With a mass only about 3.8 times larger than our sun and a diameter of only 15 miles, the black hole is very close to the minimum size predicted that black holes come from dying stars.

"This black hole is truly at the borders. For many years, the astronomers wanted to know the smallest possible size of a black hole, and this little guy is a big step toward answering this question," says Nikolai Shaposhnikov lead author of NASA's Goddard Space Flight Center in Greenbelt, Md.

Goddard Shaposhnikov and Lev Titarchuk his colleagues presented their results at the American Astronomical Society's High Energy Astrophysics Division meeting in Los Angeles, Calif. Titarchuk also works at George Mason University in Fairfax, Va., and the U.S. Naval Research Laboratory in Washington, DC .

The tiny black hole is in a binary system, Milky Way known as XTE J1650-500, named after its celestial coordinates in the southern constellation Ara. NASA's Rossi X-ray Timing Explorer (RXTE) satellite detected the scheme in 2001. Astronomers realized J1650 soon after the discovery that it holds a normal star and a relatively small black hole. But the black hole of mass had never been measured at high precision.

The method used by Shaposhnikov and Titarchuk has been described in several papers in the Astrophysical Journal. It uses a relationship between black holes and the inner part of their surrounding disks, where gas spirals inward before making the fatal plunge. When the feeding frenzy reaches a moderate rate, hot gas piles up near the black hole and radiates a torrent of X-rays. The X-ray intensity varies in a pattern that repeats itself over a nearly regular interval. This signal is called a quasi-periodic oscillation, or QPO.

Astronomers have long suspected that a QPO's frequency depends on the black hole's mass. In 1998, Titarchuk realized that the congestion zone lies close in for small black holes, so the QPO clock ticks quickly. As black holes increase in mass, the congestion zone is pushed farther out, so the QPO clock ticks slower and slower. To measure the black hole masses, Shaposhnikov and Titarchuk use archival data from RXTE, which has made exquisitely precise measurements of QPO frequencies in at least 15 black holes.

Last year, Shaposhnikov and Titarchuk applied their QPO method to three black holes whose masses had been measured by other techniques. In their new paper, they extend their result to seven other black holes, three of which have well-determined masses. "In every case, our measurement agrees with the other methods," says Titarchuk. "We know our technique works because it has passed every test with flying colors."

If Shaposhnikov and Titarchuk application of their method on XTE J1650-500, they calculated a mass of 3.8 Suns, with a margin of uncertainty of only half a sun. This figure is well below the previous record holder black hole with a reliable mass measurement, Gro 1655-40, tips the scales at about 6.3 Suns.

Here are some unknown critical threshold, a dying star, a neutron star instead of a black hole. Astronomers think the boundary between black holes and neutron stars is somewhere from 1.7 to 2.7 solar masses. Knowledge of this dividing line is important for basic research in physics, because they say scientists about the behavior of matter if it is scrunched conditions for the extremely high density.

Despite the small size of the new record holder, future space transportation systems, travelers had better watch out. Smaller black holes as in J1650 exercise tidal forces stronger than the much larger black holes in the centers of galaxies, the young guys more dangerous to approach. "If you ventured too close to J1650-black hole, whose gravity would tidally stretch your body into a strand of spaghetti," says Shaposhnikov.

Shaposhnikov adds that RXTE is the only instrument that high-precision timing observations made for this line of research. "RXTE is absolutely crucial for this black hole mass measurements," he says.

The Earth's Magnetic Field

Why did the earth a magnetic field? The electrical conductivity of molten plasma of the Earth's Core should be able to damp the current magnetic field only in thousands of years. But our five billion years old earth clearly causes magnets, to (defined) to the north. The secret is not known yet, but thought recently, in connection with earth movements in the liquid outer core. In particular, as parts of the outer core cool and fall inwards, oceans of liquid iron-rich magma to the outside world, forced to filter a helical motion by the spin of the earth. This movement, many geologists now believe that regenerates Earth's magnetism. In the picture above, a computer simulation shows the resulting magnetic field lines out to two Earth radii, with blue lines directed inwards and yellow lines directed to the outside world.

Leonids vs. The Moon

Beautiful and bright, the 2002 Leonid meteors fought against blatant moonlight. This victory example from Tuesday morning skies above Laughlin, Nevada, USA, a fearless Leonid strokes between the familiar constellation of Orion (left) and a full moon overexposed. As expected, the Leonid shower packed a double punch on 19 November with the planet Earth fall by two thick clouds of meteroids, dusty debris left by the passage of the comet Tempel-Tuttle. Some European observers reported 10 or so meteors per minute in the first peak in the vicinity of 4:00 Universal Time, while North American skygazers witnessed slightly lower rates in the vicinity of the second peak at 10:30 UT. Overall, observed rates were much lower than last year Leonid meteor storm, but for many the sky was still filled with a rewarding spectacle of bright meteors. And this performance can be a fond farewell for the coming years. The annual Leonid meteor shower is not likely to approach these rates again until the end of this century.

The Sharpest View of the Sun

This stunning picture shows remarkable and mysterious details in the vicinity of the central dark region of a planet-sized sunspot in one of the sharpest views ever from the surface of the sun. Just released, the picture was taken with the Swedish solar telescope now in its first year of operation on the Canary island of La Palma. In addition to the functions described as hair and dark channels are visible in the bright cores threads that are in the sunspot, which hitherto unknown and unexplored solar phenomena. The filaments "new, dark seeds are visible at that thousands of kilometres long, but only about 100 km wide. The solution offers 100 km wide or less is a milestone in astronomy and solar technology has been achieved here using sophisticated adaptive optics, digital image processing stacks, and processing techniques to combat the effects of atmospheric blurring. At optical wavelengths, these images are even sharper than current space-based observatories can produce solar. Incorporated on July 15, 2002, the sunspot shown, is the largest the group of sunspots cataloged as solar active region AR 10030