The traditional picture of galaxy growth is not pretty. In fact, it’s a kind of cosmic cannibalism: two galaxies are caught in ominous tango, eventually melding together in a fiery collision, thus spurring on an intense but short-lived bout of star formation. Now, new research suggests that most galaxies in the early Universe increased their stellar populations in a considerably less violent way, simply by burning through their own gas over long periods of time.
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Full story at Universe Today.
Showing posts with label stellar evolution. Show all posts
Showing posts with label stellar evolution. Show all posts
Friday, July 1, 2011
Wednesday, March 9, 2011
Cosmology 101: The Present
Welcome back! Last time, we discussed the first few controversial and eventful moments following the birth of our cosmos. Looking around us today, we know that in the span of just a few billion years, the universe was transformed from that blistering amalgam of tiny elementary particles into a vast and organized expanse just teeming with large-scale structure. How does something like that happen?
Read more...
Full story at Universe Today
Read more...
Full story at Universe Today
Saturday, January 15, 2011
The greatest story ever told.
13.7 billion years ago, an event occurred. Space itself swelled terrifically into being. Suddenly, there appeared a burgeoning cosmos where before there had been nothing. The explosion left behind a molten sea of charged particles that would eventually give life to everything in the universe. The churning plasma expanded along with space for 300,000 years until its constituent protons and electrons had finally cooled enough to combine. Consequently, the entire universe was soon clouded by neutral hydrogen gas. Such gas absorbs radiation exceptionally well, and so space was plunged into darkness for another billion or so years.
At this point, it was gravity that dispelled the haze. Clumps of gas soon condensed under its influence, slowly becoming dense furnaces for nuclear fusion. The high energy UV radiation emitted by these young stars leaked out across the universe, heating the surrounding gas to temperatures they had not faced since the big bang. Electrons that had been trapped within the nuclei of light atoms were suddenly released, reionizing hydrogen and rendering space transparent once more. As the universe expanded, overdense regions of structure contracted under gravity. Over the course of a few billion years, a familiar cosmos took shape. Stars came together into galaxies, galaxies came together into clusters, wacky objects like quasars came and went, supernovae went off, our Solar System formed, and the universe painstakingly plodded into its current configuration.
You may have noticed that some details are a little murky. As of yet, astronomers have no idea how the first stars formed out of the ambient fog. One pair of scientists is now hoping to change that. Alan Rogers of MIT and Judd Bowman of Arizona State University have developed a method using the 21cm spectral line of hydrogen. This line appears in the spectra of hydrogen atoms that have undergone an excitation. According to Rogers and Bowman, the specific way in which the radio spectrum of hydrogen evolves with time tells us that reionization itself lasted about 5 million years. Thus, the first stars and galaxies were most likely born during this time. Understanding the stellar mechanics that occurred during reionization is one of the most active quests in cosmology today. The team hopes to learn more with future observation and fine-tuning of their instrument, the EDGES antenna at the MIT Haystack Observatory.
At this point, it was gravity that dispelled the haze. Clumps of gas soon condensed under its influence, slowly becoming dense furnaces for nuclear fusion. The high energy UV radiation emitted by these young stars leaked out across the universe, heating the surrounding gas to temperatures they had not faced since the big bang. Electrons that had been trapped within the nuclei of light atoms were suddenly released, reionizing hydrogen and rendering space transparent once more. As the universe expanded, overdense regions of structure contracted under gravity. Over the course of a few billion years, a familiar cosmos took shape. Stars came together into galaxies, galaxies came together into clusters, wacky objects like quasars came and went, supernovae went off, our Solar System formed, and the universe painstakingly plodded into its current configuration.
You may have noticed that some details are a little murky. As of yet, astronomers have no idea how the first stars formed out of the ambient fog. One pair of scientists is now hoping to change that. Alan Rogers of MIT and Judd Bowman of Arizona State University have developed a method using the 21cm spectral line of hydrogen. This line appears in the spectra of hydrogen atoms that have undergone an excitation. According to Rogers and Bowman, the specific way in which the radio spectrum of hydrogen evolves with time tells us that reionization itself lasted about 5 million years. Thus, the first stars and galaxies were most likely born during this time. Understanding the stellar mechanics that occurred during reionization is one of the most active quests in cosmology today. The team hopes to learn more with future observation and fine-tuning of their instrument, the EDGES antenna at the MIT Haystack Observatory.
Sunday, June 20, 2010
A star is born: Infant star causes a stir in the astonomical community.
Call it slapping hydrogen gas on its proverbial butt. A team of American and German astronomers has announced its observation of the youngest known stellar object ever, according to a paper published in the most recent issue of The Astrophysical Journal. The fledgling star bears the poetic name L1448-IRS2E and was observed developing in the Perseus star-forming region, 800 million light years away. Stellar objects of this age are notoriously difficult to observe because they are not yet true stars and do not give off much light. The team of astronomers discovered L1448-IRS2E by detecting radiation emitted by dust surrounding the object.
A group of young stars in the Perseus constellation. Image courtesy of NASA.
Stars form out of molecular clouds when an overdense area of hydrogen begins to collapse under the influence of gravity. As the clump of gas becomes more massive, it begins to draw in gas and dust from the surrounding area. This "prestellar" phase lasts until the object forms a core that is dense and hot enough to fuse hydrogen into helium. It can then be called a protostar. Due to high-velocity streams of gas being ejected from its center, L1448-IRS2E is believed to have passed the prestellar phase; however, it is not emitting enough light to truly be called a protostar.
The object was originally discovered using Nasa's Spitzer Space Telescope and the Submillimeter Array in Hawaii. The team plans to continue observing with the newly launched Herschel telescope and hopes that its research will shed some light on the mechanics of early stellar evolution.
A group of young stars in the Perseus constellation. Image courtesy of NASA.
Stars form out of molecular clouds when an overdense area of hydrogen begins to collapse under the influence of gravity. As the clump of gas becomes more massive, it begins to draw in gas and dust from the surrounding area. This "prestellar" phase lasts until the object forms a core that is dense and hot enough to fuse hydrogen into helium. It can then be called a protostar. Due to high-velocity streams of gas being ejected from its center, L1448-IRS2E is believed to have passed the prestellar phase; however, it is not emitting enough light to truly be called a protostar.
The object was originally discovered using Nasa's Spitzer Space Telescope and the Submillimeter Array in Hawaii. The team plans to continue observing with the newly launched Herschel telescope and hopes that its research will shed some light on the mechanics of early stellar evolution.
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