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Mount Vesuvius is a stratovolcano located on the western side of Italy, near Naples. It rises to an altitude of 1,281 meters above sea level; although the height of the volcano changes after each eruption. Vesuvius is best known for its devastating eruption in AD 79, which destroyed the towns of Pompeii and Herculaneum, burying the region under meters of ash, and killing an estimated 10,000 – 25,000 people.
It’s believed that the caldera of Mount Vesuvius started forming around 17,000 years ago and this was enlarged by further eruptions. It started forming because this is a point where the African Plate is being subducted beneath the Eurasian Plate. In the past, the larger cone on Vesuvius was Monte Somma, but it’s now lower than the main cone. The volcano Vesuvius continues to erupt regularly. The last eruption was in 1944, and then 1926, and in 1906. With this history, it’s just a matter of time before it has another eruption.
Although Italians remember the volcano’s history of eruptions, they continue to live on its slopes. There are productive vineyards part way down the mountain, growing in the rich volcanic soil. And an estimated 3 million people live in a region that could be affected if Vesuvius erupts again. Emergency planners in the region have developed a strategy to evacuate 600,000 people from the region if a severe eruption is expected.
We have written many articles about volcanoes for Universe Today. Here’s an article about stratovolcanoes, and here’s an article about Mount Etna; another dangerous volcano in Italy.
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Did you know that volcanoes can make glass? Well, it’s not exactly the kind of glass you’d want to put in your house. It’s called obsidian, and it’s a naturally occurring volcanic glass formed when felsic lava flows from a volcano and then cools without crystal growth.
In a regular eruption, lava pours out of a volcano out onto the surface travels a distance downhill, and then hardens. Although a lava flow might have a thin solid crust, it might take months or even years to fully cool. As it cools, crystals form in the rock. These crystals are larger in the core of the rock, which has taken longer to cool.
In order to get obsidian, the lava erupting from a volcano needs to cool so fast that crystals in the rock don’t have a chance to form. You’ll often get obsidian when lava from a volcano is pouring into a lake or ocean and cools quickly. And glass, unlike crystals, has no regular structure and can therefore fracture in long curved shapes. Obsidian consists mostly of silicon dioxide (70% or more) – that’s the same as window glass. The black color comes from minerals dispersed in the glass, like magnetite or hematite.
If you could hold a piece of obsidian in your hand, it’s usually black or dark grey and very shiny and glasslike. It’s often cracked and broken with sharp edges. You can see than ancient people had many uses for obsidian, since it can hold a very sharp edge. In fact, surgeons to this day have found that obsidian can hold a sharper edge than even the hardest surgical steel.
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Lakes are formed by many different geologic processes, but one of the most dramatic is a maar. A maar is a low-relief crater caused by a phreatomagmatic eruption. This is a situation where ground water comes in contact with lava or magma and the resulting steam causes an explosion. This digs out a hole in the ground, creating the maar crater. And then, it usually fills back in to create a lake. The word “maar” comes from the German word, which is derived from the Latin word “mare” (sea).
Maars can occur anywhere in the world where magma comes in contact with ground water, and can range in size from 10 meters to 8 km across. They’re surrounded by a low rim composed of loose fragments of volcanic rocks and rocks torn from the ground when the explosive eruption happened. They can be 10 to 200 meters deep.
The largest known maar is found on the Seward Peninsula in northwest Alaska, and range in size from 4-8 km across. These maars are so large because the magma encountered large regions of permafrost, creating huge explosions.
A maar is related to a tuff ring. In the case of a tuff ring, the crater edge is raised above ground level. An even more dramatic tuff cone can rise up 300 meters above the surroundings.
Meteor crater in Arizona was once thought to be a maar, but geologists now know that it was created by a meteor impact about 50,000 years ago.
We have written many articles about volcanoes for Universe Today. Here’s an article about the parts of a volcano, and here’s an article about dormant volcanoes.
It’s Wednesday (already?!) so that means its time for another “Where In The Universe” challenge to test your visual knowledge of the cosmos. This week’s image was submitted by UT reader Rob Bowman, and Rob is hoping to stump everyone this week. Try to guess/name where in the Universe this image is from, and give yourself extra points if you can name the spacecraft responsible for the image. Make your guess and post a comment, but please no links to the answer. Check back sometime on Thursday to find the answer and see how you did. Good luck!
UPDATE: The answer has now been posted below.
Rob certainly chose wisely with this image, as almost everything about the life cycle of stars is right here. This is a giant galactic nebula, NGC 3603, taken with the Wide Field Planetary Camera 2 on board Hubble that was just returned back to Earth from the servicing mission. There is a lot going on in this image, as it captures various stages of the star life cycle in one single view. To the upper left of center is the evolved blue supergiant called Sher 25. The star has a unique circumstellar ring of glowing gas that is a galactic twin to the famous ring around the supernova 1987A.
The grayish-bluish color of the ring and the bipolar outflows (blobs to the upper right and lower left of the star) indicates the presence of processed (chemically enriched) material. Near the center of the view is a so-called starburst cluster dominated by young, hot Wolf-Rayet stars and early O-type stars.
A torrent of ionizing radiation and fast stellar winds from these massive stars has blown a large cavity around the cluster. The most spectacular evidence for the interaction of ionizing radiation with cold molecular-hydrogen cloud material are the giant gaseous pillars to the right of the cluster. These pillars are sculptured by the same physical processes as the famous pillars Hubble photographed in the M16 Eagle Nebula.
Dark clouds at the upper right are so-called Bok globules, which are probably in an earlier stage of star formation. To the lower left of the cluster are two compact, tadpole-shaped emission nebulae. Similar structures were found by Hubble in Orion, and have been interpreted as gas and dust evaporation from possibly protoplanetary disks (proplyds). This true-color picture was taken on March 5, 1999.
Thanks to Rob Bowman for submitting this image – particularly timely because of the Hubble Servicing mission that was completed last week.
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A volcano hotspot is a region on the Earth’s surface that has experienced volcanism for a long time. A good example of this is the Hawaiian Islands. Each of the islands in the long chain were created by the same volcano hot spot. The volcano built up an island that extended above the surface of the ocean, and then plate tectonics carried the island away, creating an extinct volcano. But there’s always a new volcano being created by the same hot spot.
There are dozens of volcano hot spots around the world, with the Hawaiian Island chain just being the most well known. Others include the Azores hotspot, the Canary hotspot and the East Australia.
About 30 km below the surface of the Earth is the mantle, a region where temperatures can reach thousands of degrees Celsius. But that’s under the continents. Underneath the oceans, the mantle is only 10 km down or less. Molten rock can seep out of the mantle and form vast magma chambers beneath the Earth’s crust. This magma finds its way to the surface, creating volcanoes.
Geologists believe that volcano hotspots are created when a narrow stream of hot mantle convects up from the Earth’s core-mantle boundary. This stream is known as a mantle plume.
Another theory is that hotspots are created when asteroids impact the Earth. The shockwave of the impact causes seismic waves to ripple through the Earth and create a hotspot on the exact opposite point on the Earth from the impact. This is known as the antipodal pair impact theory.
One of the most dramatic volcano hotspots wasn’t here on Earth but on Mars; the hotspot that created the largest volcano in the Solar System – Olympus Mons. Scientists believe that plate tectonics ceased on Mars billions of years ago, but the same volcanic hotspot kept pushing up magma. This allowed Olympus Mons to continue growing for billions of years, and reach its current height of 27 km.
We have written many articles about volcanoes for Universe Today. Here’s an article about dormant volcanoes, and here’s an article about extinct volcanoes.
Astronomers have probed closer than ever to a supermassive black hole lying deep at the core of a distant active galaxy that was once thought to be shrouded in dust — which will greatly advance the look captured in this NASA file image from the mid-1990s. Using new data from ESA’s X-ray Multi-Mirror Mission (XMM)-Newton spaceborne observatory, researchers peered into the innermost depths of the object, which lies at the heart of the galaxy known as 1H0707-495.
“We can now start to map out the region immediately around the black hole,” says Andrew Fabian, at the University of Cambridge, who headed the observations and analysis.
Artist's conception of a black hole. Credit: ESA
The galaxy — known as 1H0707-495 — was observed during four 48-hr-long orbits of XMM-Newton around Earth, starting in January 2008.
X-rays are produced as matter swirls into a supermassive black hole, illuminating and reflecting from the matter before eventually accreting into it. Iron atoms in the flow can be observed in the reflected light, affected by the speed of the orbiting iron atoms, the energy required for the X-rays to escape the black hole’s gravitational field, and the spin of the black hole. All these features indicate that the astronomers are tracking matter to within twice the radius of the black hole itself.
XMM-Newton detected two bright features of iron emission in the reflected X-rays that had never been seen together in an active galaxy. These bright features are known as the iron L and K lines, and they can be so bright only if there is a high abundance of iron. Seeing both in this galaxy suggests that the core is much richer in iron than the rest of the galaxy.
Statistical analysis of the data revealed a time lag of 30 seconds between changes in the X-ray light observed directly, and those seen in its reflection from the disc. This delay in the echo enabled the size of the reflecting region to be measured, which leads to an estimate of the mass of the black hole at about 3 to 5 million solar masses.
The observations of the iron lines also show that the black hole is spinning very rapidly and eating matter so quickly that it verges on the theoretical limit of its eating ability, swallowing the equivalent of two Earths per hour.
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The Mars Science Laboratory rover, scheduled for launch in 2011, now has a new name, thanks to a sixth-grade student from Kansas. Twelve-year-old Clara Ma submitted the winning entry, “Curiosity” in the name-the-rover contest for schoolchildren, sponsored by NASA. “We have been eager to call the rover by name,” said Pete Theisinger, who manages the JPL team building and testing Curiosity. “Giving it a name worthy of this mission’s quest means a lot to the people working on it.”
For winning the naming contest, Clara gets to sign her name directly on the rover. But you can send your name to Mars with Curiosity, too.
A NASA panel selected the name following a nationwide student contest that attracted more than 9,000 proposals via the Internet and mail. The panel primarily took into account the quality of submitted essays. Name suggestions from the Mars Science Laboratory project leaders and a non-binding public poll also were considered.
“Students from every state suggested names for this rover. That’s testimony to the excitement Mars missions spark in our next generation of explorers,” said Mark Dahl, the mission’s program executive at NASA Headquarters in Washington. “Many of the nominating essays were excellent and several of the names would have fit well. I am especially pleased with the choice, which recognizes something universally human and essential to science.” Clara Ma
Ma decided to enter the rover-naming contest after she heard about it at her school.
“I was really interested in space, but I thought space was something I could only read about in books and look at during the night from so far away,” Ma said. “I thought that I would never be able to get close to it, so for me, naming the Mars rover would at least be one step closer.”
“Curiosity is an everlasting flame that burns in everyone’s mind. It makes me get out of bed in the morning and wonder what surprises life will throw at me that day,” Ma wrote in her winning essay. “Curiosity is such a powerful force. Without it, we wouldn’t be who we are today. Curiosity is the passion that drives us through our everyday lives. We have become explorers and scientists with our need to ask questions and to wonder.”
Astronaut John Grusnfeld on the recent Hubble servicing mission. Credit: NASA
Why do we explore? In the days of Magellan, Columbus and da Gama, undoubtedly the average person thought it was foolish to risk lives and spend large amounts of money to find out what was beyond the horizon. Those explorers didn’t find what they expected, but their explorations changed the world.
What drives us to explore and discover is what we don’t know, and the spirit of exploration inspires us to create and invent so that we can go explore and possibly change the world. We don’t know yet exactly what we’ll find if humans ever go to Mars, Europa or beyond, but if we stay in our caves we’ll never find out. Similarly, space probes and telescopes like Hubble, as well as ground-based telescopes have helped us explore remotely and have facilitated the discovery of so many things we didn’t know — and didn’t expect — about our universe.
However, exploration takes money.
The most often-used argument against space exploration is that we should use that money to alleviate problems here on Earth. But that argument fails to realize that NASA doesn’t just pack millions of dollar bills into a rocket and blast them into space. The money NASA uses creates jobs, providing an opportunity for some of the world’s brightest minds to use their talents to, yes, actually benefit humanity. NASA’s exploration spurs inventions that we use everyday, many which save lives and improve the quality of life. Plus, we’re expanding our horizons and feeding our curiosity, while learning so, so much and attempting to answer really big questions about ourselves and the cosmos.
NASA’s annual budget for fiscal year 2009 is $17.2 billion. The proposed budget for FY 2010 would raise it to about $18.7 billion. That sounds like a lot of money, and it is, but let’s put it in perspective. The US annual budget is almost $3 trillion and NASA’s cut of the US budget is less than 1%, which isn’t big enough to create even a single line on this pie chart. A few other things to put NASA’s budget in perspective:
Former NASA administrator Mike Griffin mentioned recently that US consumers spend more on pizza ($27 billion) than NASA’s budget. (Head nod to Ian O’Neill)
Miles O’Brien recently brought it to our attention that the amount of money Bernie Maddof scammed with his Ponzi scheme ($50 billion) is way bigger than NASA’s budget.
Americans spend a lot of money on some pretty ridiculous things. Returning to that oft-used phrase about spending the money used in space to solve the problems on Earth, consider this: *
Annually, Americans spend about $88.8 billion on tobacco products and another $97 billion on alcohol. $313 billion is spent each year in America for treatment of tobacco and alcohol related medical problems.
Likewise, people in the US spend about $64 billion on illegal drugs, and $114.2 billion for health-related care of drug use.
Americans also spend $586.5 billion a year on gambling. Italian’s also spend quite a bit – according to Stranieri, in 2011 gamblers in Italy spent more than 100 billion euros on gambling!
It’s possible we could give up some other things to help alleviate the problems in our country without having to give up the spirit of exploration.
*the numbers used here are from various years, depending on what was readily available, but range from the years 2000 and 2008.
Computer simulation showing the development and evolution of the disk of a galaxy such as the Milky Way. Credit: Rok Roškar
The Milky Way has been around a long, long time. The age of our galaxy is approximately 13.6 billion years, give or take 800 million years. But how did the galaxy get here? What did baby photos of the Milky Way look like?
First off, there weren’t always stars in the Universe, and the Milky Way hasn’t been around forever. After the big bang happened, and the Universe cooled for a bit, all there was was gas uniformly spread throughout. Small irregularities allowed the gas to coalesce into larger and larger enough clumps, heating up and eventually starting the nuclear fusion that powers stars. The stars started to gravitationally attract each other into larger groups. The oldest of these groups of stars are called globular clusters, and some of these clusters in the Milky Way galaxy date back to the very, very early Universe.
Not all of the stars in the Milky Way date back to the primordial Universe, though. The Milky Way produces more than 7 stars per year, but it acquired much of its mass in another fashion. The Milky Way is often referred to as a “cannibal” galaxy, because during formation it swallowed up smaller galaxies. Astronomers think that this is how many larger galaxies have come to be the size they are today.
In fact, the Milky Way is currently gobbling up another galaxy, (and a stellar cluster) at this very moment. Called the Canis Major Dwarf Galaxy, the remnant stars are 45,000 light years from the galactic center, and a mere 25,000 light years from our Sun.
Older stars in the Milky Way are to be found distributed spherically in the galactic halo, meaning that it’s likely the galaxy had a spherical shape to start out. Younger stars in the galaxy are located in the disk, evidence that as it started to get heavier, the mutual orbit of material started the galaxy spinning, which resulted in the spiral one sees in representations of the Milky Way.
To get you started on how the formation of our galaxy looked, here’s an animated simulation of what a galaxy much like the Milky Way looks like as it goes from the gas cloud at the beginning of the Universe to a beautiful barred spiral, a few billion years condensed into a couple of short minutes. And to get a handle on the formation of a spiral arms in a galaxy, check out this spiral galaxy simulator.
M82. The VLA image (top left) clearly shows the supernova (SN 2008iz). Credit: MPIfR
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Supernovae are extremely luminous explosions of stars and cause bursts of radiation that often outshine an entire galaxy. So, when a supernova exploded last year in a nearby galaxy, why didn’t we see it? Was this an undercover supernova; a top-secret, covert event? Well, kind of. The secret is in the dust.
M82 is an irregular galaxy in a nearby galaxy group located 12 million lightyears from Earth. Despite being smaller than the Milky Way, it harbors a vigorous central starburst in the inner few hundred lightyears. In this stellar factory more stars are presently born than in the entire Milky Way. M82 is often called an ‘exploding galaxy’, because it looks as if being torn apart in optical and infrared images as the result of numerous supernova explosions from massive stars. Many remnants from previous supernovae are seen on radio images of M82 and a new supernova explosion was long overdue. For a quarter of century astronomers kept an eye on M82, hoping to catch a supernova in the act, but with no luck. Astronomers were starting to wonder why the galaxy has been so silent in recent years.
However, a recent explosion actually did occur in M82, and it was the closest supernova in the last five years. But the explosion was shrouded by gas and dust, leaving it invisible to our human eyes, and visible only in radio wavelengths. Astronomers say without the obscuration, this explosion would have been visible even with medium-sized amateur telescopes.
On April 9, 2009, Dr. Andreas Brunthaler from the Max Planck Institute for Radio Astronomy noticed something unusual in the data of M82 taken just the previous day with the Very Large Array (VLA) of the National Radio Astronomy Observatory in New Mexico, USA. “I then looked back into older data we had from March and May last year, and there it was as well, outshining the entire galaxy!” he said. Observations taken before 2008 showed neither pronounced radio nor X-ray emission at the position of this supernova. The Very Large Array. Credit: MPIfR
On the other hand, observations of M82 taken last year with optical telescopes to search for new supernovae showed no signs of this explosion. Furthermore, the supernova is hidden on ultraviolet and X-ray images. The supernova exploded close to the center of the galaxy in a very dense interstellar environment.
Astronomers began to realize they had perhaps found the clue to the mystery about the long silence of M82. Actually, it hasn’t been silent and perhaps many supernova events have occurred, and are something like “underground explosions”, where the bright flash of light is covered under huge clouds of gas and dust and only radio waves can penetrate this dense material. “This cosmic catastrophe shows that using our radio telescopes we have a front-row seat to observe the otherwise hidden universe”, said Prof. Heino Falcke from Radboud University.
Radio emission can be detected only from core collapse supernovae, where the core of a massive star collapses and produces a black hole or a neutron star. It is produced when the shock wave of the explosion propagates into dense material surrounding the star, usually material that was shed from the massive progenitor star before it exploded.
By combining data from the ten telescopes of the Very Long Baseline Array (VLBA), the VLA, the Green Bank Telescope in the USA, and the Effelsberg 100m telescope in Germany, using the technique of Very Long Baseline Interferometry (VLBI), the team was able to produce images that show a ring-like structure expanding at more than 40 million km/h or 4% of the speed of light, typical for supernovae. “By extrapolating this expansion back in time, we can estimate the explosion date. Our current data indicate that the star exploded in late January or early February 2008,” said Brunthaler.
Only three months after the explosion, the ring was already 650 times larger than Earth’s orbit around the Sun. It takes the extremely sharp view of VLBI observations to resolve this structure which is as large as a 1 Euro coin seen from a distance of 13.000 km.
The asymmetric appearance of the supernova on the VLBI images indicates also that either the explosion was highly asymmetric or the surrounding material unevenly distributed. “Using the super sharp vision of VLBI we can follow the supernova expanding into the dense interstellar medium of M82 over the coming years and gain more insight on it and the explosion itself,” said Prof. Karl Menten, director at the MPIfR.
Discoveries like this supernova will be routine with the next generation of radio telescopes, such as the Low Frequency Array (LOFAR) which is currently under construction in Europe, the Allen Telescope Array (ATA) in the USA, or the planned Square Kilometer Array (SKA). These will have the capability to observe large parts of the sky continuously.
Lead image description: Zooming into the center of the galaxy M82, one of the nearest starburst galaxies at a distance of only 12 Million light years. The left image, taken with the Hubble Space Telescope (HST), shows the body of the galaxy in blue and hydrogen gas breaking out from the central starburst in red. The VLA image (top left) clearly shows the supernova (SN 2008iz), taken in May 2008. The high-resolution VLBI images (lower right) shows an expanding shell at the scale of a few light days and proves the transient source as the result of a supernova explosion in M82.
Graphics: Milde Science Communication, HST Image: /NASA, ESA, and The Hubble Heritage Team (STScI/AURA); Radio Images: A. Brunthaler, MPIfR. (Click image for higher resolution).
