Thursday, February 28, 2013

Stars Dying Endlessly - Part One: The Fate of our Sun.


This is the way the world ends. Not with a bang, but as a cinder. In the three seconds it would take you to read that parody of T.S. Eliot, our Sun will transmute some 2.1 billion tons of hydrogen into helium. In the process, 14.7 million tons of matter simply vanish, directly becoming the energy that, among other things, makes life possible on planet Earth. In the 20th century alone, the Sun's core lost 15.5 quadrillion - 15,500,000,000,000,000 - tons of matter.

The Sun has been consuming itself in this fashion for the past five billion years, burning hydrogen to produce the radiation pressure needed to counteract the relentless inward pull of its own gravity. Despite this enormous rate of fuel consumption, astronomers believe the Sun has enough hydrogen left in its core to remain a relatively stable main sequence star for another seven billion years.

But as the Sun's core loses mass, its temperature and density must increase to maintain hydrogen equilibrium. When the Sun was an infant it was slightly smaller, cooler, and dimmer than it is today. As its rate of nuclear fusion slowly increases in the eons ahead, it will continue to expand and more energy will radiate from it. In other words, our Sun will get brighter. That’s not an immediate problem for a star. But it's a death sentence for planet Earth.

Over the next several hundred million years, the Sun's increasing temperature will accelerate the evaporation of Earth's oceans, driving up the opacity of our atmosphere and eventually triggering a runaway greenhouse effect. Ultraviolet radiation will break down the water molecules in our atmosphere and the component hydrogen in H2O will escape into space. Earth will begin to resemble Venus.

Within a little more than one billion years, Earth's once teeming oceans will disappear as surface temperatures soar above the boiling point of water, turning a once-verdant world into a lifeless, burned-out cinder. Still, our slowly brightening Sun will remain on the main sequence for some six billion years beyond Earth's hellish demise, before finally exhausting the hydrogen in its core. At that point, the core's proton-proton chain of fusion reactions will stop, the radiation pressure that supports the star's overlying layers will suddenly drop, and the core will collapse due to the force of gravity. Hydrogen in a shell around the core will continue burning, but the core's collapse will heat this shell and cause it to expand. As the radius of the Sun grows, its surface temperature will consequently drop off. But the Sun's luminosity, the rate at which energy radiates from a star, will increase dramatically and the Sun will become a bloated red giant.

The effect as viewed from an orbiting planet - could any one survive to see it - would be awesome. Reddish and bloated, it will appear 50 degrees across in the Earth's sky, quadruple the angular size of Orion and (if we ignore the inevitable slowing of terrestrial rotation) will take over three hours to rise and set. The Sun's core - now only planet size - has a temperature of nearly 90 million degrees Fahrenheit. It resists further compression not by fusion but by a quantum mechanical effect known as degenerate gas pressure, in which electrons with identical properties cannot be crammed closer together. Eventually, gravitational contraction pushes temperatures high enough to trigger the fusion of helium nuclei into carbon.

Because the core is degenerate gas, this temperature increase does not immediately cause the core to expand. Instead, it causes the rate at which helium is converted into carbon to accelerate in a burst called a helium flash. Eventually, core temperatures reach more than 600 million degrees, the electrons become "non-degenerate" and the core expands and cools off a bit as helium transforms into carbon. Hydrogen burning continues in a shell around the helium-burning core.

But the helium burns relatively quickly. Once it's gone, fusion stops and the electrons in the Sun's carbon core becomes degenerate. Once again, the star expands, this time to truly gargantuan proportions. Just how big is open to question, but recent calculations indicate its outer layers may reach or even exceed Earth's present orbit. If it overtakes our now-molten planet, the Earth will actually orbit inside the Sun's low-density envelope. Friction with the gases will cause it to lose orbital energy and spiral inward, eventually to be utterly destroyed along with Venus and Mercury. Mars likely will be spared, and the heat may be enough to render conditions springlike on the outer planets.

During this second period of expansion, nuclear energy will be supplied by shells of hydrogen and helium, which will shut down and re-ignite in a self reinforcing feedback loop. As the end approaches explosive helium flashes will come closer and cloer together and the Sun's luminosity will rise and fall up to 50 percent over periods as short as a few decades. These explosions will spawn a super wind that will blow away the Sun's outermost layers, creating a spectacular planetary nebula.

In the Sun's interior, nuclear reactions will finally grind to a halt. The naked core that is left behind will have about six-tenths of the Sun's original mass jammed into a hot, ultra-dense sphere about the size of Earth. This is not massive enough to generate the gravitational energy needed to fuse carbon into heavier elements. And so, less than 100,000 years after our Sun's second period of expansion begins, its core will become a white dwarf, a stellar ember that slowly dims as its pent-up heat radiates away over billions of years.

Such is the fate of the vast majority of stars in the universe, those between 0.1 and 8 times as massive as our Sun. Smaller stars never reach the main sequence at all, becoming degenerate before fusion reactions can begin. These are brown dwarfs. Stars between 0.1 and about 0.4 solar masses fuse hydrogen into helium but never get hot enough to fuse helium into carbon; they end up as helium-rich white dwarfs. Stars like our Sun evolve into carbon-rich white dwarfs, while slightly heavier ones develop the heat to fuse carbon into oxygen; they become oxygen-rich white dwarfs.

The very rare stars with masses between 8 and 30 times that of our Sun face a different fate. Because they burn so hot and fast, they can fuse heavier and heavier elements as they struggle to maintain their hydrostatic equilibrium. They end up with compact cores of solid iron, surrounded by shells of lighter elements. Eventually these massive stars undergo a supernova explosion - stay tuned for part two!

Image Description: A white dwarf lurks within the shroud like remains of the planetary nebula NGC 2440. Planetary nebulae have nothing to do with planets but are the clouds that result from the death of a star the size of our Sun. This dwarf is so hot - perhaps 360,000 degrees Fahrenheit - that it illuminates its surrounding nebula.

Image Credit Image credit: NASA/R. Ciardullo (PSU)/H. Bond (STScI)

Sources:
http://www.nasa.gov/multimedia/imagegallery/image_feature_584.html
http://www.universetoday.com/18847/life-of-the-sun/
http://imagine.gsfc.nasa.gov/docs/science/know_l2/dwarfs.html
http://science.nationalgeographic.com/science/space/universe/white-dwarfs-article/



COULD WE/ SHOULD WE EXPLORE ALPHA CENTAURI


Whether a major asteroid impact or simply the Sun’s ever-warming radiation or demise, eventually Earth will become uninhabitable. The human species, if it is to survive, must learn to travel to other worlds. Such a voyage, over billions even trillions of miles and kilometers, seems impossible, an idea notable only in science fiction or of the unimaginable future. Or is it?

If the nearest star system to our Earth, Alpha Centauri, does harbor rocky planets similar to Earth as new evidence suggests, there may be a host of ways to get us there, at least in theory.

Sending a person from Earth to Alpha Centauri within an average human lifetime wouldn't be easy. Alpha Centauri is 4.37 light-years away, more than 25.6 trillion miles away. That’s more than 276,000 times the distance from the Earth to the Sun. Recognizing that interstellar travel would, at very best, take decades, some experts are now considering transporting the DNA and other resources necessary to recreate humans on an unmanned spacecraft.

Beginning with the development of a rocket engine that can reach high velocity, we are not short of initiative, but even with engines based on photon-powered sails or nuclear fusion, we are still a long way from reaching the speed of light. At a maximum speed of about 17,600 mph (about 28,300 kph), it would take a modern rocket ship about 165,000 years to reach Alpha Centauri. Other propulsion methods considered include antimatter engines, giant electromagnetic fields to suck in hydrogen to fuel a nuclear rocket and light sails that would run off not just light generated by the Sun but could also ride laser beams fired carefully at those ships to give an extra boost, especially when sails were too far away to catch much light from our sun.

With the discovery of numerous exoplanets our hopes need not depend solely upon Alpha Centari as the lone oasis in the quest for interstellar travel. But if the science to get us there advances the pursuit of prolonged human space travel at warp speeds, then on to Alpha Centari.


http://www.space.com/5094-alpha-centauri.html
http://www.dailygalaxy.com/my_weblog/2012/01/the-80000-year-voyage-to-alpha-centauri-carrying-the-dna-necessary-to-recreate-humans-.html

Image Credit: Artist rendition of part of the Centauri Star system



CHARLES MESSIER & HIS CATALOG OF DEEP SKY OBJECTS


Charles Messier was a French astronomer with a particular interest in comets. To organize his work and observations, he prepared the Messier Catalog (1784) which became synonymous in astronomy with deep sky objects (DSOs).

Born in Lorraine, France June 26, 1730, he began the study of astronomy early. In 1744, at the age of 14, he saw his first comet and later witnessed the 1748 annular solar eclipse.

He joined the Paris Observatory at 21 years old. As an assistant to Nicholas Delisle he became an accomplished astronomer. Although spotted in 1858 by Johann Georg Palitzsch, Messier was the first person in France to find Halley's Comet.

He became a dedicated comet hunter and was nick-named the “comet ferret” by King Louis XV. Discovered between 1760 and 1784, thirteen comets would bear his name and he would co-discover several more. Along with the comets he sought after, Messier also discovered forty nebulae.

The reason Messier compiled his catalog of DSOs was to save astronomers time while comet hunting. A long time is taken for an astronomer to recognize a potential comet suspect as it requires checking for a sustained change in observed position in the sky over a period of time. His telescope was a small refractor only a couple of inches in diameter, so even star clusters would appear fuzzy like a comet. He recorded the stationary objects - star clusters, nebulae and galaxies - so he could differentiate between previous observations of the object or a possible new comet. He made a careful sketching of each, naming them M-objects (for Messier) followed by a catalog number, beginning with M1 indicating the Crab Nebula. He recorded a total of 103 entries.

In April 1817, Charles Messier passed away at the age of 86, at his home in Paris. Seven objects known to have been recorded by Messier were added to the catalog in the twentieth century, with the final entry, M110, added in 1967. His catalog is still widely used by astronomers for identification of DSOs and contains some of the most beautiful objects in the sky.


Find a complete listing of the Messier Catalog here:http://astronomycentral.co.uk/m1-m10/

Information Source(s):
http://www.space.com/16686-charles-messier-biography.html
http://messier.seds.org/xtra/history/CMessier.html
Image Credit:



PLUTO’S ATMOSPHERE


A team of scientists from the University of Virginia have run a new simulation of Pluto’s upper atmosphere, showing that the atmosphere may extend as far as 10,390 kilometres (6,456 miles) into space. Stray molecules from the atmosphere may even be deposited on its largest moon, Charon. The team combined two previous models of Pluto’s atmosphere so they could get a better estimate of the molecules’ escape route into space. The calculated escape rate was slightly smaller; however this change caused a larger change in the structure of the atmosphere.

Pluto’s atmosphere, such that it is, is predominantly comprised of methane, nitrogen and carbon monoxide which likely come from ice on the surface of the dwarf planet. The atmosphere changes in size as Pluto moves closer and further from the Sun. When Pluto is closer to the Sun in its elliptical orbit, the Sun’s heat causes the ice to evaporate and gases subsequently escape into space. This continues until Pluto moves far enough away from the Sun for the heat to fade; the ice begins to build up. Pluto’s orbit around the Sun takes 248 Earth years; its last approach to the Sun was in 1989.

NASA will be sending the New Horizons probe to Pluto in 2015. Researchers are trying to pinpoint the escape route of the gases in Pluto’s atmosphere to determine where the spacecraft should be looking. It has been difficult for scientists to work out the size of Pluto’s atmosphere due to debate about the best way to measure it. Its atmosphere is heated by infrared and ultraviolet light from the Sun; ultraviolet light is absorbed into the atmosphere closer to the planet. Farther away from the planet however the atmosphere is so thin that the ultraviolet light affects the molecules. For these reasons, researchers use ultraviolet heating models for the upper atmosphere.

The molecules that escape from Pluto’s atmosphere move through the thermosphere, which is where a lot of the ultraviolet light is absorbed in the atmosphere. This heating drives the escape process for the molecules. The exosphere is the top of Pluto’s atmosphere; this is where the atmosphere is so thin that collisions between particles do not happen as frequently as other sections of the atmosphere. The boundary between the thermosphere and the exosphere is called the exobase. Scientists are not sure where this boundary is for Pluto, and the mathematical models for each part of the atmosphere are different; this makes calculating the size of Pluto’s atmosphere problematic.

This new model includes the solar maximum (when Pluto is warmest) and the solar medium. The researchers also assumed a diameter for Pluto of 2,300 kilometres (1,429 miles), though the accepted measurements range by 100 km (62 miles).

The image is an artist’s impression of how the surface of Pluto might look. The image shows patches of pure methane on the surface.


http://www.space.com/18628-pluto-atomosphere-larger.html
http://arxiv.org/pdf/1211.3994v1.pdf

Image credit: ESO/L. Calçada



Honouring a Hero


The US House of Representatives unanimously passed a bill late Monday to rename NASA’s Dryden Flight Research Center located at Edwards Air Force Base in Southern California to the Neil A Armstrong Flight Research Center. At the same time, the Western Aeronautical Test Range will be renamed to honor aeronautical engineer Hugh L Dryden.

"Dryden recommended to President John F. Kennedy that the goal of putting a man on the moon within 10 years was achievable and something the American people could rally behind," said Texas Congressman Lamar Smith, the chairman of the House Science, Space, and Technology Committee. "The rest is history. President Kennedy grabbed Hugh Dryden's idea and addressed a joint session of Congress the very next month. The Apollo program was the brainchild of Hugh Dryden."

Armstrong was, of course, the first person to ever step foot on the moon. Few people know, however, that from 1955-1962, he was employed as a test pilot at the center, which was then called the High-Speed Flight Station. It was here that he flew Dryden’s X-15 rocketplane. During this time, he also helped to develop the concept for the Lunar Landing Research Vessel, which eventually led to the development of the training vehicle that he, along with Buzz Aldrin and Michael Collins, used to practice for the Moon Landing.

"Dryden was not able to see his dream become reality, as he died in 1965," added Smith. "And unfortunately, Neil Armstrong passed away last August. It is important for us to honor both men's legacies by naming the Flight Research Center after Neil Armstrong and the surrounding Test Range after Hugh Dryden."

Neil Armstrong died of complications from a cardiovascular procedure on August 25, 2012. This is at least the third time since 2007 that such a bill has been passed in the House of Representatives, and the first since his passing. The next step is for it to go before the United States Senate, let’s hope it finally passes.

The image below is an aerial view of the Dryden Flight Research Center.


For further reading go to:

http://www.space.com/19967-neil-armstrong-nasa-center-name.html

http://www.nasa.gov/centers/dryden/home/index.html

Image Credit: NASA




A newly discovered comet will pay Mars a very close visit in October 2014, and the outside chance of an impact has not been ruled out at this point. Astronomers are still calculating the trajectory of the comet, named C/2013 A1 (Siding Spring) to determine just how close the icy visitor will come to the Red Planet. “Even if it doesn’t impact, it will look pretty good from Earth, and spectacular from Mars,” wrote Australian amateur astronomer Ian Musgrave.

The comet was discovered on 3 January 2013 by comet-hunter Robert McNaught at the Siding Spring Observatory in New South Wales Australia. After the initial discovery was made, astronomers at the Catalina Sky Survey in Arizona looked back through previous observations and found prior images of the comet dating back to 8 December 2012. Using these earlier findings and the newer data gathered since the early January discovery, scientists are able to plot the trajectory of the comet through its flyby of Mara on 19 October 2014.

Estimating the closest approach is a challenge, and each new piece of data will allow further refinement of the calculations. Just to show how variable this can be, yesterday’s best estimate was that the comet would pass approximately 109,200 km from Mars. Today, new astrometric data from the ISON-NM observatory indicates that the comet will pass less than 37,000 km from the planet’s surface! That should virtually guarantee that Mars will pass through the coma (the gaseous envelope surrounding the comet) as C/2013 A1 whizzes by the planet.

At the time of closest approach, the comet will be moving along at 56 km/s relative to Mars. Based on the current estimate of the absolute magnitude of the nucleus, the comet could have a diameter of of up to 50 kilometers. If those estimates hold true, and if the comet were to impact the surface, it could leave a crater 500 km in diameter and 2 km deep.

Observations will continue, and measurements will be refined further as more data comes in. One thing is for sure: there should be some great images to look forward to in October 2014.

Image caption: artists conception of a comet streaking through Martian skies.


Image credit: Chris Smith / NASA
Sources: http://www.universetoday.com/100298/is-a-comet-on-a-collision-course-with-mars/#more-100298
http://spaceobs.org/en/tag/c2013-a1-siding-spring/
http://www.iceinspace.com.au/forum/showthread.php?p=950710
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1%3Bcad%3D1#cad





Close Cometary Encounter For Mars


A newly discovered comet will pay Mars a very close visit in October 2014, and the outside chance of an impact has not been ruled out at this point. Astronomers are still calculating the trajectory of the comet, named C/2013 A1 (Siding Spring) to determine just how close the icy visitor will come to the Red Planet. “Even if it doesn’t impact, it will look pretty good from Earth, and spectacular from Mars,” wrote Australian amateur astronomer Ian Musgrave.

The comet was discovered on 3 January 2013 by comet-hunter Robert McNaught at the Siding Spring Observatory in New South Wales Australia. After the initial discovery was made, astronomers at the Catalina Sky Survey in Arizona looked back through previous observations and found prior images of the comet dating back to 8 December 2012. Using these earlier findings and the newer data gathered since the early January discovery, scientists are able to plot the trajectory of the comet through its flyby of Mara on 19 October 2014.

Estimating the closest approach is a challenge, and each new piece of data will allow further refinement of the calculations. Just to show how variable this can be, yesterday’s best estimate was that the comet would pass approximately 109,200 km from Mars. Today, new astrometric data from the ISON-NM observatory indicates that the comet will pass less than 37,000 km from the planet’s surface! That should virtually guarantee that Mars will pass through the coma (the gaseous envelope surrounding the comet) as C/2013 A1 whizzes by the planet.

At the time of closest approach, the comet will be moving along at 56 km/s relative to Mars. Based on the current estimate of the absolute magnitude of the nucleus, the comet could have a diameter of of up to 50 kilometers. If those estimates hold true, and if the comet were to impact the surface, it could leave a crater 500 km in diameter and 2 km deep.

Observations will continue, and measurements will be refined further as more data comes in. One thing is for sure: there should be some great images to look forward to in October 2014.

Image caption: artists conception of a comet streaking through Martian skies.


Image credit: Chris Smith / NASA
Sources: http://www.universetoday.com/100298/is-a-comet-on-a-collision-course-with-mars/#more-100298
http://spaceobs.org/en/tag/c2013-a1-siding-spring/
http://www.iceinspace.com.au/forum/showthread.php?p=950710
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2013A1%3Bcad%3D1#cad



White Dwarfs and life beside them


Scientists widen their perspective hunting planets that harbor life. According to a new theoretical study of Earth-like planets orbiting white dwarf stars, oxygen in such planets could be more easily detected than in planets orbiting a Sun-like star (where oxygen would indicate life). Best part: we might be able to detect such a planet within the next decade, thanks to NASA’s James Webb Telescope (JWST).

A white dwarf is what remains after a star like our Sun dies. It puffs of its outer layers leaving a hot core that can be about the size of the Earth. It is much smaller and fainter than the Sun, but it can give enough heat to a nearby world for billions of years. Before becoming a white dwarf though, a star swells into a red giant, destroying any nearby planets. Thus, any planet would either have to arrive in the habitable zone afterwards or form from the disks of dust that reportedly surround white dwarfs.

How does life relate? Well, certain biomarkers in a planet’s atmosphere (like oxygen, or methane) indicate the presence of life. Such biomarkers are elements that regenerate with the help of biological processes. For example, oxygen in our atmosphere is constantly replenished by plant and algae. Should all life suddenly vanish, oxygen would decline as it would oxidize rocks and dissolve in the oceans. So, large quantities of oxygen in a distant planet would likely mean life there.

Scientists use photometry to determine the consistency of a planet’s atmosphere. Light coming from the parent star of that planet passes though the atmosphere and is absorbed by certain elements that exist there. Thus, more light than normal will be blocked at particular wavelengths, and using that signature, scientists can determine the elements present.

As the new study shows, white dwarfs are a lot better to observe than Sun-like stars. Problems would arise observing planets around normal stars, as the extreme faintness of the biomarker signals would “hide” in the glare of the parent star. In white dwarfs though, the dim light will greatly enhance our ability to see the O2 biomarker in particular. JWST could perform those observations.

Problem is exoplanets have yet to be found around white dwarfs. However, several evidence suggest they exist, like dust disks around them. Still, scientists must first find one before observing it.

Looking forward to the JWST launch.


The paper: http://arxiv.org/abs/1301.4994
Sources: http://www.astrobio.net/exclusive/5352/detecting-life-on-planets-that-orbit-white-dwarf-starshttp://www.sciencedaily.com/releases/2013/02/130225131618.htm

Image: Artist’s impression of a planet orbiting a white dwarf. Hydrogen gas ejected from the star as it evolved from a red giant to a white dwarf, is seen as a blue ring (Credit: David A. Aguilar(CfA))



White Dwarfs and life beside them


Scientists widen their perspective hunting planets that harbor life. According to a new theoretical study of Earth-like planets orbiting white dwarf stars, oxygen in such planets could be more easily detected than in planets orbiting a Sun-like star (where oxygen would indicate life). Best part: we might be able to detect such a planet within the next decade, thanks to NASA’s James Webb Telescope (JWST).

A white dwarf is what remains after a star like our Sun dies. It puffs of its outer layers leaving a hot core that can be about the size of the Earth. It is much smaller and fainter than the Sun, but it can give enough heat to a nearby world for billions of years. Before becoming a white dwarf though, a star swells into a red giant, destroying any nearby planets. Thus, any planet would either have to arrive in the habitable zone afterwards or form from the disks of dust that reportedly surround white dwarfs.

How does life relate? Well, certain biomarkers in a planet’s atmosphere (like oxygen, or methane) indicate the presence of life. Such biomarkers are elements that regenerate with the help of biological processes. For example, oxygen in our atmosphere is constantly replenished by plant and algae. Should all life suddenly vanish, oxygen would decline as it would oxidize rocks and dissolve in the oceans. So, large quantities of oxygen in a distant planet would likely mean life there.

Scientists use photometry to determine the consistency of a planet’s atmosphere. Light coming from the parent star of that planet passes though the atmosphere and is absorbed by certain elements that exist there. Thus, more light than normal will be blocked at particular wavelengths, and using that signature, scientists can determine the elements present.

As the new study shows, white dwarfs are a lot better to observe than Sun-like stars. Problems would arise observing planets around normal stars, as the extreme faintness of the biomarker signals would “hide” in the glare of the parent star. In white dwarfs though, the dim light will greatly enhance our ability to see the O2 biomarker in particular. JWST could perform those observations.

Problem is exoplanets have yet to be found around white dwarfs. However, several evidence suggest they exist, like dust disks around them. Still, scientists must first find one before observing it.

Looking forward to the JWST launch.


The paper: http://arxiv.org/abs/1301.4994
Sources: http://www.astrobio.net/exclusive/5352/detecting-life-on-planets-that-orbit-white-dwarf-starshttp://www.sciencedaily.com/releases/2013/02/130225131618.htm

Image: Artist’s impression of a planet orbiting a white dwarf. Hydrogen gas ejected from the star as it evolved from a red giant to a white dwarf, is seen as a blue ring (Credit: David A. Aguilar(CfA))



Life on Europa?


Europa is the second of the four Galilean moons of Jupiter, when counted outwards from the planet. First observed by Galileo Galilei in 1610, all four moons can be easily seen with a small telescope or binoculars. Europa is the smallest of the four, but still only slightly smaller than Earth's Moon.

Europa is considered by many planetary scientists to be the most likely place in our Solar System to harbour life, besides Earth. It is very cold on the surface, between 50 K and 110 K (-220 C to -160 C), but it's abundant in water. Our understanding of Europa's inner structure is based mostly on photographs taken by spacecraft, in particular the Galileo probe during its many flybys of the moon.

Europa is covered with a crust of ice, estimated to be 10-30 km thick, but planetary models indicate that underneath it there should be liquid ocean, as deep as 100 km. As Europa's eccentric orbit moves it closer or farther from Jupiter, the planet's tidal forces change in strength causing the moon to elongate slightly and then relax to its rounder shape. This constant squeezing and pulling is thought to generate enough heat to keep the ocean from freezing completely.

Europa has an atmosphere that's made mostly of oxygen. It is quite thin, with the surface pressure a trillion times lower than Earth's. The oxygen is not thought to be of biological origin. It's likely a result of molecules of water being split into oxygen and hydrogen by solar ultra-violet radiation and charged particles from Jupiter's magnetosphere.

A mission to Europa to examine it up close and to look for signs of life is being proposed by NASA's Jet Propulsion Laboratory together with Johns Hopkins University, Maryland. The spacecraft named Clipper would be launched in 2021 and enter an orbit of Jupiter some 3 years later to focus on flybys of Europa. The mission hasn't yet been funded so its future is uncertain, but exploring the moon is high on the list of priorities for future planetary exploration. ESA is planning to launch its own spacecraft JUICE (Jupiter Icy Moon Explorer) around the same time (2022) that would target also Ganymede and Callisto.

The image taken by Galileo in 1998 shows the surface of Europa with its characteristic lines and freckles, thought to be a result of liquid water or warmer ice erupting through to the surface of the moon.


For more about Jupiter and its moons, check our recent postings:
http://www.facebook.com/photo.php?fbid=479261188805725&set=a.458569147541596.111543.334816523250193&type=1
http://www.facebook.com/photo.php?fbid=479261642139013&set=a.458569147541596.111543.334816523250193&type=1

More about Europa, the possibility of life there and plenty of images:
http://solarsystem.nasa.gov/europa/faq.cfm

Source:
http://phys.org/news/2013-02-jupiter-europa-moon-likeliest-life.html

Image credit: NASA/JPL/University of Arizona/University of Colorado



CIRCUMZENITHAL ARC OVER CABO POLONIO


This image was taken in Cabo Polonio, Uruguay in February 2012 by Vanesa Amarelle, around 3pm in very hot weather. Circumzenithal arcs form when downcoming sunrays enter the uppermost horizontal face of oriented plate crystals and then leave through a vertical side face. The result is the refraction of rays that produce very pure and well-separated prismatic colours; they look like upside-down rainbows.

Cabo Polonio is a caserío (hamlet), found on the tip of a moon-sliver shaped peninsula in the eastern coast of Uruguay in the Rocha Department.


See a previous post on circumzenithal arcs here:http://on.fb.me/ZAnhqM
More on Cabo Polonio here: http://www.cabopolonio.com/
Image: Vanesa Amarelle



THE ART OF GEOLOGY: Volcano View of Unzen, Japan


A volcano can be a beautiful thing to observe; most of us observe them in safety via photos and film, or with luck, get to watch the volcano at Kilauea. This illustration of the Unzen Volcano near ancient Shimabara is even more: it is a scientific illustration that has become a work of art. It is also one of the few images to commemorate Japan’s most terrifying volcanic event.

Unzen is a complex of stratovolcanoes on the island of Kyushu. It is active and has a long history of eruptions; the oldest eruptions date to 6 million years, and the youngest, well, are still in progress. The latest severe activity reported by the USGS consists of a series of pyroclastic flows (ash eruptions and lahars) that occurred between 1991 and 1995. The worst, however, was in 1792 when the 4000 year old Mayu-yama lava dome erupted with a series of dacitic lavas. Silica-rich dacites are among the most dangerous types of lavas: they are hard viscous lavas (the more silica in a lava, the greater its tendency to form strong silicate molecules bonding its internal structure and making flow difficult), and rather than flow as do the basalts of Hawaii, they tend to cause explosive eruptions. The eruption instigated a massive landslide that devastated Shimabara in its passing, continued into the sea, where it then generated a massive tsunami: 15,000 people were killed in the debris landslide and subsequent tsunami, making it Japan’s worst volcano- related catastrophe.

This image is a map of the Unzen Volcano documenting flows and destruction published as a book plate in 1822. Its author, Issaac Titsingh, was a member of the Royal Society, a surgeon, and a lawyer. While a member of the East Indian Company (between about 1765 and 1799), he worked in Japan and has become known as a “Japanologist.” His map is the closest thing to a scientific eye-witness account of the region following the 1792 eruption and catastrophic tsunami.

And his geologic map – it’s a piece of art!


Image from “"Illustrations of Japan consisting of private memoirs and anecdotes of the reigning dynasty of the Djogouns, or sovereigns of Japan..." by Isaac Titsingh, London: R. Ackermann, 1822”

http://maps.nationmaster.com/country/ja/1
http://www.volcanodiscovery.com/japan.html
http://vulcan.wr.usgs.gov/Volcanoes/Japan/description_unzen.html
http://books.google.gr/books/about/Secret_Memoirs_of_the_Shoguns.html?id=BLzQA7cpr7wC&redir_esc=y



Earth’s atmosphere


Earth’s atmosphere is an amazing thing, when you think about it. Without our atmosphere life would be unsustainable here on Earth; but what exactly is it? 

The atmosphere is simply a layered mixture of gases, mainly nitrogen (78%), Oxygen (21%) and a mixture of argon, water vapour, carbon dioxide, methane and trace gases. These combined create not only the air we breathe, but also help serve as a sun screen, a temperature regulator and of course protect us from asteroid impacts (most of the time!).

The innermost layer of our atmosphere, and probably the most familiar to us, is the troposphere. Here and up until around 15km from the surface is where the majority of our planets weather systems reside and is where nearly 80% of the Earth’s air is located. The name “troposphere” comes from a Greek word that refers to mixing and this is exactly what happens within the troposphere, as warm air rises to form clouds, rain falls, and winds stir the lands below.

Past the troposphere we discover the stratosphere; a less dense region of the atmosphere which extends out to around 50km. Here, the oxygen molecules are transformed into ozone which forms a protective layer against harmful ultraviolet light from the sun- the importance of this layer has been made evident in our lifetimes; without which, skin cancer rates would be undoubtedly higher. Seeing as ultraviolet energy is being absorbed in this region, the stratosphere has quite extravagant differentials in temperature. At the base of the stratosphere it is extremely cold, around -80 degrees Celsius, at its top, the temperature rises to nearly 0 degrees Celsius.

After the stratosphere comes the mesosphere and here is where a lot of action happens. Any meteors which enter our atmosphere tend to be destroyed in the mesosphere; they “burn up” and never reach the Earth’s surface. This layer, which extends to 85 kilometres from the surface, is one of the fundamental reasons why Earth isn’t covered in meteor craters- if the moon had a mesosphere it would be a much smoother surface.

Next comes the ionosphere- named for the ions created within this layer from energetic particles of sunlight and space. The ionosphere allows for the transmission of radio signals which are invaluable, particularly before the days of satellite communication. Here is also were the auroras are created and who doesn’t love them, eh? The International Space Station has also made its home in the ionosphere.

Lastly, we have the exosphere. This tenuous portion of the Earth's atmosphere extends outward until it interacts with the solar wind. Solar storms compress the exosphere. When the Sun is tranquil, the layer can extend further outward. The reach of this layer varies between 1,000 and 10,000 kilometres, where it merges with interplanetary space.


Together, all these layers make our atmosphere which, sadly, is continually menaced by human activity. Between rising carbon dioxide levels and air pollution, ozone destruction and acid rain, we have divorced our relationship with our environment. It is important not to forget the delicacy which is life here on Earth, we should aim to maintain a mutually beneficial relationship with what has supported our time here on this lovely blue planet. After all, if the relationship is irreconcilable, the environment will get the house... !


Some further information and reading for you:

http://www.ucar.edu/learn/1_1_1.htm

http://www.atmos.illinois.edu/earths_atmosphere/earth_atmosphere.html

Photo was taken from the ISS (credit: NASA/SPL)

Tropical Cyclone Rusty In Pilbara


Cyclone Rusty is a Category 3 cyclone and has made its way very slowly towards the Pilbara, in the North of Western Australia (http://on.fb.me/Y1FahY). It was upgraded to Category 4 at 8am GMT+8 but has been downgraded to Category 3. Australia’s Tropical Cyclone Category System extends from 1 to 5; a Category 3 severe tropical cyclone is equivalent to a Category 1 Hurricane on the US Saffir-Simpson category scale (http://bit.ly/15PDcFY).

At 5:00pm GMT+8 Rusty crossed the coast at 5pm at Pardoo, 110 kilometres east northeast of Port Hedland and will now move inland and gradually weaken. Wind gusts up to 165kmh are expected near the cyclone centre; winds exceeding 230kmh are likely to develop. Rusty is expected to weaken below cyclone intensity overnight Thursday and winds are expected to gradually ease in Port Hedland tonight.The wind gusts near the centre of the cyclone at 6:00pm GMT+8 were 205 kilometres per hour and weakening; the central pressure was 952 hectoPascals.

Highly dangerous winds and rain are expected to continue until Thursday. More than a dozen schools in the area have been closed, hundreds of homes are without power and people in low-lying areas of Port Hedland have been urged to relocate because of the possibility of a storm surge in the area.

People from Pardoo to Whim Creek including Port Hedland and South Hedland, are on "red alert"; they may need to stay sheltered for up to 36 hours. People in the adjacent inland areas including Marble Bar should go to shelter immediately. People in communities between Wallal and Pardoo, extending inland to Nullagine are on “yellow alert” and need to take action and get ready to shelter from a cyclone. Those in communities between Sandfire and Wallal and between Nullagine and Newman are on “blue alert” and need to prepare for cyclonic weather.

Perth Weather Live will issue their next advice by 9:00 pm GMT+8 Wednesday 27 February.

If you are in a cyclone-affected area, please ensure you have:
• A portable, battery-operated radio and spare batteries
• Torches (recommended in preference of candles)
• A supply of tinned or dehydrated food for four days
• At least three litres of water, per person, per day, for four days
• Emergency lighting
• Suitable clothing and footwear
• A first-aid kit and essential medicines

A map showing the track of the cyclone is available at:
http://www.bom.gov.au/cyclone

The image was taken on Barrow island, 50 kilometres northwest of the Western Australia coast; it shows the first signs of Cyclone Rusty.


http://www.bom.gov.au/products/IDW60281.shtml
http://www.karrathases.org.au/index.php/be-prepared/58-stay-indoors-during-a-red-alert
https://www.facebook.com/perthweatherlive?fref=ts
Image: @cristymacqueen

Wind Power Grows


According to a new report by the Global Wind Energy Council the amount of wind energy generating capacity grew by 19% in 2012. The total amount of capacity is now at 282,000 megawatts (MW). We’ve seen that wind generated electricity is now on par with other sources when it comes to price (http://on.fb.me/13lQ8np) and its showing.

China and the US are leading the way with more than 13,000 MW of new generation capacity last year. Brazil leads South America with 1,077 MW of new capacity bringing them to 2500 MW, while Germany and the UK lead in Europe with more than 3500 MW of new capacity in 2012.

The report linked below has nice graphs and charts showing breakouts by region, country, and offshore vs. onshore capacity.


Photo: Norwegian University of Science and Technology

References:

http://www.gwec.net/wp-content/uploads/2013/02/GWEC-PRstats-2012_english.pdf

http://www.winddaily.com/reports/Global_wind_energy_capacity_grows_19_percent_in_2012_999.html



Mount Nyiragongo


Nyiragongo is an active stratovolcano located on the border between the Democratic Republic of Congo and Rwanda. The volcano is associated with the Albertine rift- the rift splitting the Somalian plate away from the rest of the African plate. The geology of the area comprises of mountains made of uplifted pre-Cambrian basement, overlaid by more recent volcanic activity. 

The summit is 1.2km is diameter and contains the worlds most active lava lake. The lava lake is known for its extremely fluid lava, which has often been said to "run like water" when the lake drains. In 2002 the lava lake drained from fissures located on the western flanks of the volcano. This destroyed the central part of the closest town; Goma.

Links:

http://www.volcanodiscovery.com/nyiragongo.html

http://www.geo.arizona.edu/geo5xx/geos577/projects/kayzar/html/nyiragongo_volcano.html

Image: Carsten Peter



Siberian Cave


New evidence from Siberian caves suggests that a global temperature rise of 1.5 degrees Celsius could see a thaw in permafrost, potentially releasing further amounts of carbon into the atmosphere.

In what appears to be the vicious circle of climate change- the warming of land in Siberia has the potential to release over 1000 giga-tonnes of CO2 and CH4 (Methane) into the atmosphere. 

The data comes from an international team led by Oxford University Scientists looking at stalactites and stalagmites in caves located along Siberia’s permafrost frontier. By analysing the rock formations (using chemical analysis and radiometric dating techniques); which are the result of liquid rainwater and snow dripping into the cave, the researchers are able to analyse 500,000 years of changing permafrost conditions. The team are particularly interested in a warm period which occurred some 400,000 years ago that suggests a global temperature increase of just 1.5 degrees is enough to cause substantial thawing.

Aside from the environmental problems associated with the sudden release of carbon, there is also a significant risk with regard infrastructure. For instance, natural gas facilities in the region, as well as power lines, roads, railways and buildings are all built on permafrost and are vulnerable to thawing. Some 24% of the Northern hemisphere is covered by permafrost - but it looks that this figure may reduce significantly in the coming years. 


Image is an Icy grotto in Baikal, Olkhon Island, Siberia. (Credit: © katvic / Fotolia)

For more information, see here: http://www.ox.ac.uk/media/news_stories/2013/130222.html


Wednesday, February 27, 2013

What's on your Tounge ?


Vitamin B12 is crucial because of its highly important role in hematopoiesis: the production of blood cells. It is naturally abundant through the animals we eat, primarily clams, liver, and trout, though the animals themselves do not synthesize the vitamin. Bacteria that live symbiotically within the animals form B12 as a byproduct, which attaches to the protein. Bacteria and archaea are the only organisms capable of this synthesis.

For vegetarians, B12 fortified breakfast cereals give 100% of the recommended daily. Dietary supplements also provide an animal-free source, and while it acts fundamentally the same as natural sources, it is not readily absorbed. Research shows that only a very small fraction of the B12 provided in pill form actually gets used; the rest gets converted into incredibly bright yellow urine. For individuals who have difficulties absorbing through the digestive tract, injections are available.

Deficiencies in B12 result in symptoms of fatigue, headaches, depression, and weight loss, among others. This is easily seen on the tongue, which can turn pale, swell, and bleed.

For more information: http://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/

Photo credit: Doctorspiller

Tuesday, February 26, 2013

Contrails over Portugal and Spain


Contrails are condensation trails that form behind high-altitude aircraft. The composition of contrails is practically identical to naturally-forming cirrus clouds; naturally high levels of humidity cause the clouds to form, and contrails form when airplanes inject extra water vapour into the atmosphere through their exhaust. Air temperatures must be -39°C (-38°F) or below in order for contrails to develop.

Depending on the humidity of the air, contrails can last seconds or many hours. If the air is dry, the contrails linger in the air for seconds to a few minutes. When the air is humid, the contrails can spread outward until they are difficult to distinguish from naturally occurring cirrus clouds. Though most of the contrails in humid air last a few hours, satellites have observed clusters of contrails lasting up to 14 hours and traveling for thousands of kilometres before dissipating.

Contrails do have an impact on climate. The long-lived and spreading contrails (like the ones pictured) reflect sunlight and trap infrared radiation. Even one contrail in a clear sky reduced the amount of radiation that reaches the Earth’s surface and at the same time increases the amount of infrared radiation absorbed by the atmosphere. Until now, it has been difficult to ascertain what overall impact these two effects have on climate.

Scientists at NASA’s Langley Research Center have developed a computer algorithm that searches through data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and distinguishes between natural cirrus clouds and young- to medium-aged contrails. This allowed the scientists to estimate how much contrails contribute to overall cirrus and cloud coverage.

The group published their findings in a 2013 article in Geophysical Research Letters (http://bit.ly/ZuGmdO). The group estimated that contrails cover between 0.07% and 0.40% of the Northern Hemisphere sky in a given year. When scaled to the Southern Hemisphere, the global mean coverage would be 0.07%. Coverage is greatest during winter and least during the summer. The researchers also concluded that contrails produce a slight net warming effect on the Earth. The researchers still have the challenge of detecting the older, wider contrails, like the ones in the image shown, to better estimate their coverage and impact on climate.

This image was taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite on February 15, 2013; it shows many contrails over Portugal and Spain.


http://earthobservatory.nasa.gov/IOTD/view.php?id=80476&src=fb
Spangenberg, D. (2013, Feb. 11). Contrail radiative forcing over the Northern Hemisphere from 2006 Aqua MODIS data. Geophysical Research Letters. (http://bit.ly/ZuGmdO)
NASA image by Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response.





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