Let’s Explore Gamma-ray Bursts

Astronomers remain fascinated by gamma-ray bursts. These bursts of energy appear to be among the most powerful explosions in the universe today. They occur about once a day and are divided into two categories. The first category is called long gamma-ray bursts and last from two seconds to about thirty seconds. They have a clearly defined burst of energy followed by an afterglow which can be clearly seen. The second type is short gamma-ray bursts. These bursts last under two seconds and most last a few milliseconds.

When gamma-ray bursts were first detected in 1969, scientists believed the intense flashes of energy may have originated from distant alien civilizations. We now know that gamma-ray bursts result from the cores of massive stars collapsing at the end of their lives. These stars are known as supernovas and, if the star has enough mass, they turn into black holes. As the gas descends into the center of the black hole, some of it escapes as gamma-rays and is shot out from the dying star’s poles at nearly the speed of light.

Although gamma-ray bursts only last from a few seconds to a few minutes and are not visible to human eyes, they emit the same amount of energy the Milky Way produces in 100 years and are brighter than all other sources of gamma-rays, including neighboring stars and our Sun. Scientist have observed gamma-ray bursts from 13.14 billion light-years away, making them the most powerful forms of energy in the universe, secondary only to the big bang.

Gamma-ray bursts produce large amounts of gas that evelopes the entire surrounding area. Because new stars form from the gas clouds left behind by larger stars that have undergone the supernova process, gamma ray bursts are often found in these “stellar nurseries.” Scientists now use gamma-ray bursts to locate areas of new star formation and study the life cycle of stars.

Astronomers also believe that long gamma-ray bursts are caused by the collapse of a Wolf-Rayet star. When the star collapses, a black hole is formed within the star. Then, as the star further collapses, matter escapes from the star. It is this matter that astronomers are seeing.

These long gamma-ray bursts come from all directions within the universe. Astronomers believe that most of them originate at the very edge of where the most powerful telescopes can see and beyond. NASA and other space agencies have satellites that are studying the bursts. When they detect one, they send a signal to several points on Earth. Telescopes can then be pointed in the right direction.

Image Credit: 1) Artist’s conception of a gamma-ray burst by NASA/SkyWorks Digital

Reference:

Woosley, S., & Bloom, J. (2006). The Supernova–Gamma-Ray Burst Connection Annual Review of Astronomy and Astrophysics, 44 (1), 507-556 DOI: 10.1146/annurev.astro.43.072103.150558

Extreme Gamma-ray Burst – NASA Science. (2009, February 20). NASA Science. Retrieved February 24, 2012, from http://science.nasa.gov/science-news/science-at-nasa/2009/20feb_extremegrb/

Gamma-Ray Burst Physics. (n.d.). Astronomy and Astrophysics. Retrieved February 24, 2012, from http://www2.astro.psu.edu/users/nnp/grbphys.html

NASA – National Aeronautics and Space Administration. (2009, November 02). NASA. Retrieved February 24, 2012, from http://www.nasa.gov/mission_pages/GLAST/news/star_factories.html

NASA – National Aeronautics and Space Administration. (2011, May 27). NASA. Retrieved February 24, 2012, from http://www.nasa.gov/mission_pages/swift/bursts/swift-20110527.html

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Tellurium Detected for the First Time in Ancient Stars

Nearly 13.7 billions years ago our universe consisted of three basic elements which included hydrogen, helium, and a little bit of lithium. However, 300 million years ago when the stars first began to emerge, new elements were formed. Now there are around 100 different elements in our universe, including the rare element Tellurium.

Tellurium has been rarely found on Earth, which is why hardly anyone has ever heard of it. It is a superconductive element that was found in ancient stars near the outskirts of the Milky Way galaxy. Common elements such as Iron and Nickle can be created by any ordinary supernova, but Tellurium is in a group of heavy elements that can only be created through specialized supernovas.

During rapid nuclear fusion, heavy elements are formed creating elements such as Tellurium. It is called the r-process, which occurs when atomic nuclei become bombarded by neutrons during a supernova explosion. The result is the creation of heavier elements that are not as common as some of the lighter elements that are much more abundant. This Tellurium discovery was an interesting find for astronomers, and is yet another step towards unraveling the mystery of these special supernovas.

Image Credit: periodictable.com

Reference:

Ian U. Roederer, James E. Lawler, John J. Cowan, Timothy C. Beers, Anna Frebel, Inese I. Ivans, Hendrik Schatz, Jennifer S. Sobeck, & Christopher Sneden (2012). Detection of the Second r-process Peak Element Tellurium in Metal-Poor Stars The Astrophysical Journal Letters, 747 (1) DOI: arXiv:1202.2378

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Milky Way’s Black Hole Devouring Asteroids?

At the center of the Milky Way galaxy (encompasses our solar system) there is a black hole that features a mass of more than three million times that of the sun at its center. This black hole, known as Sagittarius A (SGR A for short), has been detected through various sources of radiation that stem from the direction of the center of the galaxy. However, SGR A has now been found to be grazing and vaporizing asteroids that pass near it according to recent data released from NASA’s Chandra X-ray Observatory. This discovery comes with the finding that there is a cloud of trillions of asteroids and comets hovering around the black hole. Such a finding redefines the current environmental criteria for an asteroid or comet to form in space.

SGR A has likely been consuming tremendous numbers of asteroids as of late as the black hole has been emanating x-ray radiation in larger quantities than usual. Black holes hold true to the notion that ‘what goes in must come out,’ so they often spit out high amounts of radiation as they consume stellar objects. The asteroids and comets from the nearby cloud that pass within approximately 100 million miles of SGR A are likely hopelessly shredded. The space rocks are destroyed due to the high tidal forces associated with the black hole’s mass which creates enormous friction. The asteroids and comets are ripped apart in a similar fashion by which Saturn forms its rings with the exception that these rocks burn up like a meteor. This discovery is just one more clue to the overall mystery of the Milky Way galaxy.

Image credit: universetoday.com

Let’s Explore Photosynthesis on Exoplanets

Imagine an astronaut stepping out of a spacecraft onto the surface of an extrasolar planet that is capable of sustaining life. Now imagine the astronaut is greeted by the sight of red colored trees and grass. Such a scenario could be more reality than science fiction because of the variances in photosynthesis theorized to exist in other parts of the Milky Way Galaxy.

Photosynthesis occurs in plants when they use sunlight to create foods from carbon dioxide and water. This process of converting energy from sunlight into chemical energy produces oxygen and causes chlorophyll to form. It is chlorophyll that is responsible for imbuing plants with a healthy green color. The reason this happens is because chlorophyll absorbs more blue and red light waves and fewer green light waves from sunlight. Reflecting the green light waves is what causes the plants to appear green to the human eye.

When the Sun in our solar system radiates light, it reaches the Earth in a particular distribution of colors. As this sunlight passes through the Earth’s atmosphere, the various gases that comprise the atmosphere filter out certain colors before they strike the surface of the Earth. Much of the color that is not absorbed in the atmosphere is red, blue or green. Plants tend to absorb a greater amount of red and blue rays and reflect back green.

Some scientists think that plant life growing under the rays of an extraterrestrial sun could reflect colors other than green after the photosynthesis process is completed. The color that is most commonly visible on alien plants correlates with how colors are distributed in the light radiated by the parent star that strikes the surface of the extraterrestrial world.

The spectral type of a main sequence star can have a direct impact on the coloring of plants. For that reason, coloring can vary from star to star if the spectral type for each star also shows some variance. In a scientific paper published in the March, 2007 issue of Astrobiology magazine, a team of scientists examined how light emitted by another sun would appear from the vantage point of a planet orbiting that host star. Nancy Kiang, author of the paper, said the scientific team determined that the atmosphere of any extrasolar Earth-like planet would feature a chemical composition that is compatible with the chemical composition of its host star. How light from that star is seen on the planet’s surface would be affected by how it is filtered through the atmosphere as it reaches the surface.

Kiang, who works with the Goddard Institute for Space Sciences at NASA, and her team conducted an extensive study where they modeled how sunlight would reach the surface of Earth-sized planets that are hospitable to life from stars of varying spectral types. Kiang’s team speculated that each planet could experience different dominant colors that emerge in plants through photosynthesis based on how hot or cool the sun is that is anchoring that solar system.

Plant life existing on other worlds is not guaranteed to mimic the appearance of plants we are accustomed to seeing on Earth. Planets revolving around a blue star could feature plant life that has a dominant color of yellow or orange and this could lend to forests that boast autumn type colors throughout the growing season on those planets. If a habitable world is located in a binary star system or multi-star system, it could cause some exotic variations in how the plant life grows and appears to the human eye after going through photosynthesis. These planets could have plants that are almost black in color.

In the case of habitable planets around red dwarf stars, all plant life would likely exist underwater. The proximity of the habitable zone around the star would make it difficult for plants to fend off ultraviolet radiation because they could not generate enough energy from infrared light through photosynthesis to create sufficient oxygen to block ultraviolet radiation penetrating the atmosphere.

The idea that differences exist in the photosynthesis process from one planet to the next changes how astrobiologists search for evidence of life on other worlds outside our own solar system. It reinforces the idea that plant and animal life alike have evolved and adapted to fit the unique conditions of this Earth as well as reinforcing the notion that life on other habitable planets would evolve to survive and thrive in a similar manner on other planets. What do you think? Is photosynthesis the same on all planets or do you think it will be vastly different?

References: 
Kiang, N., Siefert, J., Govindjee, ., & Blankenship, R. (2007). Spectral Signatures of Photosynthesis. I. Review of Earth Organisms Astrobiology, 7 (1), 222-251 DOI: 10.1089/ast.2006.0105

Kiang, N., Segura, A., Tinetti, G., Govindjee, ., Blankenship, R., Cohen, M., Siefert, J., Crisp, D., & Meadows, V. (2007). Spectral Signatures of Photosynthesis. II. Coevolution with Other Stars And The Atmosphere on Extrasolar Worlds Astrobiology, 7 (1), 252-274 DOI: 10.1089/ast.2006.0108

Artist’s Impression of an Exoplanet with Moons, Orbiting the Star HD70642 (Photo Credit: David A. Hardy, Astroart.org © PPARC)

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