Friday, June 10, 2005
Question of Quasars
Quasars are the true masters of the universe. For no object in the whole astral menagerie packs more power than they do.
They don't look like much in telescopes, but probe one closer and you'll see the most awesome object in the universe. Quasars, which were first discovered by radio astronomers in the 1950s and hence their name, Quasi-stellar Radio Sources, are an amalgam of everything the universe can offer. At the center, there's a gargantuan black hole, a billion times more massive then the sun. The black hole's maw sucks in gas and dust from a vast accretion disc and burps light, copious amount of radio waves, and jets of electromagnetic radiation. This celestial orgy is surrounded by a vast galaxy orbiting the black hole at a safe distance.
Quasars are quite old. They were around when the universe was just 850 million years old. It takes light 13 billion years to cover the distance between most quasars and us. Hence they appear in telescopes like faint dots, although they are ten trillion times more luminous than the Sun,.
Since these behemoths are so old, scientists have long wondered what happened to them and where are they today. Finally, they have some answers.
Scientists from the Virgo Consortium, a group of computational astrophysicists from European, American, Canadian and Japanese universities, have come up with the Milenium Run, a powerful computer simulation of the evolution of the universe, including the formation of galaxies and quasars. They say in a new paper published in the journal Nature that "by tracking the merging history trees of the host halos, we find that all our quasars candidates end up today as the central galaxies in rich clusters."
The Virgo Consortium says that its model also allows to "establish evolutionary links observed at different epochs” of the universe.
That's great news for proponents of the cold dark matter model (CMD), the leading theory of the evolution of the universe, observes Nickolay Gnedin, astrophysicist from the University of Colorado at Boulder. He reported in Nature that some scientists "naturally question" whether 850 million years after the Big Bang was long enough time for such gargantuan objects to form. They questioned the validity of the CMD, which describes how small, slowly moving particles of dark matter combine in larger structures in the universe, saying that the theory works too slowly and doesn't give quasars enough time to assemble.
The consortium's results put such fears to rest: "We demonstrate that galaxies with supermassive central black holes can plausibly form early enough in the standard cold dark matter cosmology to host the first known quasars, and that these end up at the centers of rich galaxy clusters today.
They don't look like much in telescopes, but probe one closer and you'll see the most awesome object in the universe. Quasars, which were first discovered by radio astronomers in the 1950s and hence their name, Quasi-stellar Radio Sources, are an amalgam of everything the universe can offer. At the center, there's a gargantuan black hole, a billion times more massive then the sun. The black hole's maw sucks in gas and dust from a vast accretion disc and burps light, copious amount of radio waves, and jets of electromagnetic radiation. This celestial orgy is surrounded by a vast galaxy orbiting the black hole at a safe distance.
Quasars are quite old. They were around when the universe was just 850 million years old. It takes light 13 billion years to cover the distance between most quasars and us. Hence they appear in telescopes like faint dots, although they are ten trillion times more luminous than the Sun,.
Since these behemoths are so old, scientists have long wondered what happened to them and where are they today. Finally, they have some answers.
Scientists from the Virgo Consortium, a group of computational astrophysicists from European, American, Canadian and Japanese universities, have come up with the Milenium Run, a powerful computer simulation of the evolution of the universe, including the formation of galaxies and quasars. They say in a new paper published in the journal Nature that "by tracking the merging history trees of the host halos, we find that all our quasars candidates end up today as the central galaxies in rich clusters."
The Virgo Consortium says that its model also allows to "establish evolutionary links observed at different epochs” of the universe.
That's great news for proponents of the cold dark matter model (CMD), the leading theory of the evolution of the universe, observes Nickolay Gnedin, astrophysicist from the University of Colorado at Boulder. He reported in Nature that some scientists "naturally question" whether 850 million years after the Big Bang was long enough time for such gargantuan objects to form. They questioned the validity of the CMD, which describes how small, slowly moving particles of dark matter combine in larger structures in the universe, saying that the theory works too slowly and doesn't give quasars enough time to assemble.
The consortium's results put such fears to rest: "We demonstrate that galaxies with supermassive central black holes can plausibly form early enough in the standard cold dark matter cosmology to host the first known quasars, and that these end up at the centers of rich galaxy clusters today.
