Thursday, February 18, 2010

Jurassic Space: Ancient Galaxies Come Together after Billions of Years.

Hickson Compact Group 31 is one of 100 compact galaxy groups catalogued by Canadian astronomer Paul Hickson. Credit: NASA, ESA, S. Gallagher (University of Western Ontario), and J. English (University of Manitoba). Photo No. STScI-PRC10-08a

Imagine finding a living dinosaur in your backyard. Astronomers have found the astronomical equivalent of prehistoric life in our intergalactic back yard: a group of small, ancient galaxies that has waited 10 billion years to come together. These "late bloomers" are on their way to building a large elliptical galaxy. Such encounters between dwarf galaxies are normally seen billions of light-years away and therefore occurred billions of years ago. But these galaxies, members of Hickson Compact Group 31, are relatively nearby, only 166 million light-years away.New images of these galaxies by NASA's Hubble Space Telescope offer a window into what commonly happened in the universe's formative years when large galaxies were created from smaller building blocks. The Hubble observations have added important clues to the story of this interacting foursome, allowing astronomers to determine when the encounter began and to predict a future merger.Astronomers know the system has been around for a while because the oldest stars in a few of its ancient globular clusters are about 10 billion years old. The encounter, though, has been going on for about a few hundred million years, the blink of an eye in cosmic history. Everywhere the astronomers looked in this compact group they found batches of infant star clusters and regions brimming with star birth. Hubble reveals that the brightest clusters, hefty groups each holding at least 100,000 stars, are less than 10 million years old.The entire system is rich in hydrogen gas, the stuff of which stars are made. Astronomers used Hubble's Advanced Camera for Surveys to resolve the youngest and brightest of those clusters, which allowed them to calculate the clusters' ages, trace the star-formation history, and determine that the galaxies are undergoing the final stages of galaxy assembly.The composite image of Hickson Compact Group 31 shows the four galaxies mixing it up. The bright, distorted object at middle, left, is actually two colliding dwarf galaxies. The bluish star clusters have formed in the streamers of debris pulled from the galaxies and at the site of their head-on collision. The cigar-shaped object above the galaxy duo is another member of the group. A bridge of star clusters connects the trio. A longer rope of bright star clusters points to the fourth member of the group, at lower right. The bright object in the center is a foreground star. The image was composed from observations made by the Hubble Space Telescope's Advanced Camera for Surveys, NASA's Spitzer Space Telescope, and the Galaxy Evolution Explorer (GALEX). The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute conducts Hubble science operations. The institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc. in Washington, D.C.

Friday, February 5, 2010

More carbon dioxide in atmosphere, more forest cover will be there to absorb it.

Increasing carbon dioxide benefits trees.
Dr. Nitish Priyadarshi

Almost 100% of the observed temperature increase over the last 50 years has been due to the increase in the atmosphere of carbon dioxide and other greenhouse gas concentrations like water vapour, methane and ozone.. The largest contributing source of carbon dioxide gas is the burning of fossil fuels. Research says more carbon dioxide more heating of the earth. This is one aspect of the carbon dioxide. Other aspect is its relation with the trees. If we believe on the researches by the scientists, increasing carbon dioxide benefits trees.

Scientists from the University of Wisconsin-Madison and the University of Minnesota at Morris have found that increased levels of atmospheric carbon dioxide have led to the rapid growth of certain tree species. The quaking aspen, a popular North America deciduous tree, has seen a 50 percent acceleration in growth over the past 50 years due to increased CO2 levels.

Trees are necessary climate regulators since they process carbon dioxide and give off oxygen. Humans process oxygen and give off carbon dioxide, working harmoniously with natural plant life to maintain proper atmospheric composition. Since natural forests represent about 30 percent of the earth’s surface, they are highly effective at segregating greenhouse gases.

For many a tree, the first response to the increase of carbon dioxide levels in the air is an increase in photosynthesis. More carbon dioxide, CO2, in the air means more sugar can be made by photosynthesis. Making more sugar pushes the tree into a growth spurt. Trunks and branches grow taller, longer, and thicker; new branches and leaves form; and roots send out more long, thin root strands covered with root hairs.

As more fossil fuels are burned than ever before, more CO2 is dumped into the air than ever before. The trees will respond with more photosynthesis and fresh growth more quickly than ever before.

Africa's tropical forests have stored huge amounts of carbon over the last four decades and become a critical sponge for greenhouse gases.

Long-term measurements taken across the continent's tropical belt showed that African forests absorb as much carbon dioxide as those in the Amazon.Tropical forests only account for seven-to-ten percent of the Earth's land area. But they hold up to half of the carbon locked inside the planet's terrestrial vegetation, giving them an outsized role in regulating greenhouse gases in the atmosphere. Forests are carbon stores, and they are carbon dioxide sinks when they are increasing in density or area.Previous studies in South America have shown that Amazonian old-growth forests have absorbed, on average, an extra 620 kilogramme (1,364 pounds) of carbon per hectare (2.47 acres) per year. About 70-80 billion tonnes of carbon dioxide are fixed annually by terrestrial and aquatic photoautotrophs.
African tropical forests are providing important ecosystem services by storing carbon and being a carbon sink, thereby reducing the rate of increase in atmospheric CO2, the main driver of global warming.

If increasing carbon dioxide benefits trees. And trees absorb carbon, then why we are so worried about increasing carbon dioxide?

Worry is that with increasing carbon dioxide, forest cover is depleting many folds either due to forest fire or due to civilized human beings. The accelerating destruction of the rainforests that form a precious cooling band around the Earth's equator, is now being recognized as one of the main causes of climate change.

So if we have to fight global warming and increasing carbon dioxide level we have to give space for more forest cover. We will have to protect growing trees which are the major consumers of carbon dioxide. Slogan like “MORE TREES, MORE OXYGEN AND LESS CARBON DIOXIDE” is more relevant in present scenario.