The First Star: By Ker Than

THE FIRST STAR: BY KER THAN

There are currently more stars in the cosmos than any one person could ever count. Our galaxy alone contains about 400 billion. But it wasn't always this way.

For many millions of years after our universe first formed no stars existed, and then there was one. That primordial star was likely a massive blazing behemoth that burned brighter and faster than any star around today.                                                                                       A new computer model now suggests that it also formed much earlier than previously thought. Other studies have estimated that the first star sparked into existence some 155 million years after our universe exploded into life in the Big Bang 13.7 billion years ago.

The new simulation indicates that this event occurred much earlier, when the universe was only 30 million years old. It also suggests that it took about another 370 million years for the first galaxy as massive as our own Milky Way to form. The model is detailed in an upcoming issue of the Monthly Notices for the Royal Astronomical Society.                                                                                                                       When exactly?

Using detailed computer simulations, astronomers reconstructed the conditions under which the first star was born and even the precise sequence of steps that occurred soon after to allow other stars, black holes and eventually galaxies, to form.                                   Astronomers suspect, for example, that the first star formed in a dense cloud of dark matter and gas. They also think that many present-day galaxies are the products of mergers between much smaller galaxies during the early days of our universe.

Estimating when the first star formed, however, has been difficult. That's because even the most powerful supercomputers can only simulate small portions of the universe at a time.

“To estimate when the first stars formed, we must remember that the first 100,000 solar mass clumps collapsed in regions that happened to have particularly high densities early on,” said study leader Rennan Barkana, an astrophysicist at the University of Tel Aviv in Israel.    “There were initially only a few such regions in the entire universe, so a simulation that is limited to a small volume is unlikely to find such [regions] until much later,” he said.

The model created by Barkana and his colleagues gets around this problem by approximating how many dark matter clumps large enough to host the first star were present at different times of the universe.                                                                                                      “We integrated this over time to find the total expected number of observable stars,” Barkana said. The researchers then crosschecked their predictions with simulations.                     Primal stars

 Even by stellar standards, the primordial star was a monster. It likely had a mass of about 100 times that of our Sun and it would have spewed out vast amounts of energetic radiation, especially in the ultraviolet range. Had human eyes been around to see it, it would have appeared blue-violet in color.

The first star shone brighter than most stars in existence today and it zipped through its stellar life in only 2 million to 3 million years, compared to the several-billion-year lifetimes that some of today's stars have. Our Sun is middle-aged now and has been around for 4.6 billion years.

Scientists think that when it spent its fuel, the first star exploded in a titanic stellar cataclysm called a supernova, flinging heavy elements forged during the star's lifetime into space (before collapsing to form a black hole), setting the stage for the next generation of stars.                                                                                                                                      “After a short time, stars began appearing in greater abundance throughout the universe,”                                                                                                  The second generation stars likely formed within about a million years after the first, Barkana said. Within five million years, there were about 100 stars; within ten million years, 10,000 celestial orbs of fire were lighting up the heavens. Unlike that first star, which was made up mostly of hydrogen and helium, the stars that came after contained heavier elements, such as carbon and iron.

                                               Still detectable                                                                                                                 Light once emitted by the first star might still be detectable, Barkana said!!!!  In space, the older an object is, the farther away it is. It would require a telescope about 100 million times more sensitive than the Hubble Space Telescope to observe light from the first star, but it's not impossible.

“If the first star was indeed massive and produced in its death a huge supernova explosion or gamma ray burst, then we might have a chance to see the explosion with the instruments planned for the coming decade,” Barkana said. 

BLACK HOLES ARE THE DRIVING FORCE OF CREATION!!!!

Black holes suffer a bad rap. Indicted by the press as gravity monsters, labelled highly secretive by astronomers, and long considered in theoretical circles as mere endpoints of cosmic evolution, these unseen objects are depicted as mysterious drains of destruction and death.                                                                                                                   So it may seem odd to reconsider them as indispensable forces of creation.

“The emerging picture of co-evolving black holes and galaxies has turned our view of black holes on its head,” says Meg Urry, an astronomer and professor of physics at Yale University. “Previously, black holes were seen as the endpoints of evolution, the final resting state of most or all of the matter in the universe. Now we believe black holes also play a critical role in the birth of galaxies.”

• Central bulges of stars in many galaxies, such as our Milky Way, are directly related to the masses of the black holes buried inside, as detailed in June of 2000. A galaxy's dimensions seem tied to its black hole's dietary habits.
• Most black hole mass seems to come from direct consumption (called accretion) of gas, indicating that a black hole needs a surrounding galaxy to grow. The dark horse
  a halo of mysterious dark matter is thought to infuse the space surrounding each of the bulge-packing galaxies. The invisible gravity generator would play a crucial role in galaxy and black hole construction.

The also-rans
If co-evolution reigns, as most researchers believe, then two older (but not-dead-yet) theories are wrong: that a galaxy forms first and directs the development of a black hole; or that a black hole is generated first, providing the seed around which a galaxy can coalesce. It is also possible that different types of galaxies form by different means, and that co-evolution will only be found to describe one path to galactic adulthood.

Earlier this month, Windhorst and a colleague, Haojing Yan, released a Hubble Space Telescope image showing the most distant “normal” galaxies ever observed.

Though stretched and distorted by the technique used to spot them (an intervening galaxy cluster was used as a “gravitational lens”), the newfound galaxies, Windhorst's team assures us, resemble our own Milky Way. They are seen as they existed more than 13 billion years ago, within 1 billion years of the Big Bang.

Practically side-by-side in time, discovered in separate observations made as part of the Sloan Digital Sky Survey, are compact but bright objects known as quasars. These galaxies-to-be shine brilliantly because, researchers believe, each has a gargantuan black hole at its core, whose mass is equal to a billion suns or more, all packed into a region perhaps smaller than our solar system.

The resulting gravity pulls in nearby gas. The material is accelerated to nearly the speed of light, superheated, and swallowed. The process is not entirely efficient, and there is a byproduct: An enormous amount of energy – radio waves, X-rays and regular light – hyper-illuminates the whole scene.

Quasars also seem to be surrounded by halos of dark matter, a cryptic and unseen component of all galaxies. Co-existing around and amongst all this, researchers are coming to realize, is a collapsing region of stars and gas as big or larger than our galaxy.                                                                                                                                            It was no coincidence that the announcements of the two findings – distant quasars and normal galaxies –were made together at a meeting of the American Astronomical Society (AAS) Jan. 9. Co-evolution was on the minds of the discoverers.

Among co-evolution's significant impacts is its ability to render mostly moot a longstanding chicken-and-egg question in astronomy: Which came first, the galaxy or the black hole? “How about both?” Windhorst asks. “You could actually have the galaxy form simultaneously around a growing black hole.”

Urry, who was not involved in either finding but was asked to analyze them, explained it this way: “We believe that galaxies and quasars are very intimately connected, that in fact quasars are a phase of galaxy evolution. In our current picture, as every galaxy forms and collapses, it has a brief quasar phase.”  So when a quasar goes dormant, what's left are the things we associate with a normal galaxy – stars and gas swirling around a central and hidden pit of matter.

Evolving idea

Demonstrations of co-evolution began to emerge in the mid-1990s when researchers found hints that the existence of a significant black hole at the center of a galaxy was related to the galaxy's shape, says Martin Haehnelt of the University of Cambridge. Only galaxies with a spherical bulge-like component appear to accommodate supermassive black holes.  Our Milky Way, if it could be viewed edge on, would display a good example of one of these galactic bulges: Imagine the profile of a stereotypical flying saucer, though with a wider and flatter disk. The Milky Way is smaller than many galaxies, however, and it has a correspondingly less massive black hole – roughly 2.6 million suns worth. It almost surely once had a quasar phase, astronomers say.                                                                                At any rate, in the mid-1990s no one knew for sure how prevalent black holes were. Theory and some observational data pointed to the likelihood that they were ubiquitous.

Evidence continues to mount. In 2001, two separate teams showed that many smaller galaxies that don't have bulges also do not seem to contain significant black holes.

Over the past six months or so, other important studies have emerged, providing independent confirmation to some of the initial work. Haehnelt: “It becomes more and more clear that supermassive black holes can significantly change the structure and evolution of galaxies.”

There are many variations on the basic theory of co-evolution. Each version attempts to explain a vexing fact: In the blink of a cosmic eye – just a half a billion years – invisible spheres of matter were born, and several gained the mass of a billion or more suns and were driving the shape and texture of swirling agglomerations of newborn stars.                                   Co-evolution is not a done deal. Perhaps, some have suggested, a huge black hole simply collapses out of a pre-galactic cloud and serves as a ready-made engine to drive further galaxy development. Even staunch supporters of co-evolution say there are still viable theories, not yet refutable, putting the immense black hole in place first, and others that have the galaxy solely responsible for driving the formation of a black hole.

“Indeed,” Sir Martin says, “there is a lot of debate about whether black holes can form in very small galaxies, and whether there is a link between the 'small' holes that form as the endpoint of the evolution of massive stars and the holes of above a million solar masses that exist in the centers of galaxies.”