Post by Chicago Astronomer - Astro Joe on Aug 12, 2006 8:21:49 GMT -6
No black holes after all?
One of the brightest and furthest known objects in the universe might not be a black hole as traditionally believed, but rather an exotic new type of object, a new study suggest
And the researchers say this raises doubts as to whether other so-called black holes are really that, either.
The astronomers are elbowing aside the time-honored concept of the black hole: a large object that compacts itself, under its own gravity, to an infinitely dense point with such gravitational strength that nothing nearby can escape its grip.
Instead, the researchers are picturing an object with a definite size, and a surprising property: it gradually crams itself into a smaller space forever, but never achieves a black hole’s infinitely small size.
Quasars, most astronomers agree, are the bright centers of galaxies billions of light-years away. A light-year is the distance light travels in a year.
Scientists traditionally picture a quasar’s core as a disc of gas spiraling into a “supermassive” black hole, which sucks it in. The bright light comes from the gas, which heats up as it races inward. Some of the gas also spews outward in two oppositely-directed jets.
Quasars appear only in the furthest reaches of the known cosmos. Astronomers reason that this is because they existed only long ago. The furthest areas are those where we see the universe as it was long ago, because it takes so long for light from those places to reach us.
Quasar-like structures also exist in the more recent, and thus nearby, universe. They persist as the “black holes” also believed to lie at the center of most galaxies. But these are dimmer than quasars. Scientists think this is because they’ve consumed much of the available gas.
Theorists have struggled to understand the workings of quasars’ jets and discs, called accretion discs. It has also been hard for observers to see the hearts of quasars, because the regions are so compact and distant.
In the new study, Rudy Schild of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. and colleagues studied a quasar known as Q0957+561, located about 9 billion light-years from Earth in the direction of the constellation Ursa Major.
This quasar holds a central compact object weighing the equivalent of 3 to 4 billion Suns. Most scientists would call it a black hole, but Schild said his findings suggest otherwise: surprisingly, it’s magnetic, unlike a black hole.
Source: www.world-science.net/othernews/060811_quasar.htm
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Interesting concept that now delves into unknown territory of inner space...
