There are three ways to describe a volcano’s activity; there can be active, dormant, or extinct volcanoes. Active volcanoes have erupted recently. A dormant volcano isn’t erupting right now, but vulcanologists expect it could erupt at any time. Extinct volcanoes haven’t erupted for tens of thousands of years, and aren’t expected to erupt again.
What causes volcanoes to go extinct? Simply put, they’re cut off from their supply of lava. This is where a chamber of magma underneath the surface of the Earth finds its way to the surface through weaknesses in the crust. A good example of this is the hotspot that created the chain of Hawaiian Islands. The tectonic plate carrying the islands is slowly moving, so that volcanoes are cut off from the hotspot underneath. Eventually they go extinct, while the hotspot creates a new volcano further to the East.
Some volcanoes look extinct, but it might just be a long time since they’ve erupted. For example, the Yellowstone Caldera in Yellowstone National Park hasn’t had a violent eruption in about 640,000 years, but scientists think it’s still active. There has been minor activity and lava flows as recently as 10,000 years ago. The region also has regular minor earthquakes and ground is lifting up in some areas, so scientists think that’s it’s still an active volcano.
Volcanoes thought to be extinct have erupted again. For example, Mount Vesuvius erupted famously in AD 79, destroying the towns of Herculaneum and Pompeii. And the Soufriere Hills volcano on the island of Montserrat resumed activity in 1995.
Other volcanoes are clearly extinct, with only the heavily eroded lava plug remaining.
We have written many articles about volcanoes for Universe Today. Here’s an article about shield volcanoes, which can sometimes be extinct. And here’s another about dormant volcanoes.
A new 60-minute documentary created especially for the International Year of Astronomy is now airing on PBS stations in the US. “400 Years of the Telescope: a journey of science, technology and thought” is a remarkable voyage through space and time, filled with stunning, high-definition footage showing not only images from space taken by observatories around the world, but also the remote and beautiful locations where our eyes on the Universe – our magnificent telescopes – sit. It also provides a tour through the evolution of telescopes since Galileo’s first astronomical observations, and how the telescope has changed our perceptions of the cosmos and ourselves. The documentary also includes interviews with scientists who helped develop the observatories, and those who have made incredible discoveries with them. Narration by astrophysicist Neil de Grasse Tyson and a beautiful original score of music complete this wonderful documentary that you won’t want to miss. Check here for airing times on your local station. This video is also available for purchase.
But the documentary doesn’t end with airing on television. This is a multi-faceted production including extensive web content and planetarium shows. Universe Today had the chance to talk with the writer/director/producer of the project, Kris Koenig of Interstellar Studios. To find out more about this entire project, enjoy our interview, below, and make sure you watch the trailer for the show, above.
Universe Today: This sounds like a wonderful project. Can you tell us more about everything that is involved with “400 Years of the Telescope?”
Kris Koenig: This is a multi-faceted production, beginning with a high-definition documentary for PBS. We’re also creating a full dome planetarium show (Two Small Pieces of Glass) that will also be stepped down to all the different formats for different planetarium domes. We’ve been filming with a 4K camera, which means the production will be able to transition to an IMAX. So there’s an IMAX program, a public television documentary, and a planetarium program. In addition to that, we are partnering with PBS affiliates around the country through a grant through the National Science Foundation that will allow us to coordinate with the Astronomical Society of the Pacific to do events throughout the year based on the initial and subsequent broadcasts of the show. We’ll be encouraging people to go to the science centers and planetariums to watch the planetarium show, and then when they step outside, there to meet them will be local astronomers with telescopes.
What we’re doing is exactly the goals of IYA, which is to educate, and encourage people to go out and have a telescopic experience. That’s what we hope to achieve with that production.
Also, we knew from the beginning that we wanted a lot of web content. We conducted over 70 hours of interviews, which of course, we couldn’t include them all in the documentary. So of those 70 hours of interviews will be available on the internet, and totally downloadable and searchable by key terms. The transcript can be downloaded; there will be footage people can watch. The footage can also be downloaded and students can create their own documentaries. So this whole project can spawn a bunch of documentaries that can be used for school projects or shown locally. So we’re trying to outreach to the arts as well as into science.
(Teachers and students –Check out this link for additional educational activities.)
UT: How long have you been working on this project?
Kris Koenig. Credit: 400 Years of the Telescope Koenig: In 2005, we had just finished production of a ten-hour telecourse for PBS, for which we received two Emmy’s (Astronomy Observations and Theories, distributed by Coast Learning). I was visiting with Debbie Goodwin from Keck Observatory and she asked me, “What are you doing for IYA?” I said, “IY what?” We had actually started work on another production, which we hope we can get back to. But by the end of that week we had formed our advisory board, and initially coordinated things with a PBS station. By March we had our first launch meeting where all the advisers came together and discussed what the program should be like, what should we focus on and what should we avoid. We drafted a treatment to PBS and got a letter of encouragement back and we started the production. We brought together our planetarium partners because Peter Michaud at the Gemini telescope called me after he heard about the project and proposed joining forces to develop the content for a planetarium show. We started shooting in August of 2007.
UT: Traveling around the world to capture this must have been incredible! What stands out in your mind in creating this documentary?
Koenig: I think the thing that capped the whole project happened very early on. We were in the Institute and Museum of the History of Science in Florence, and had just finished taping Galileo’s telescope. The people there, Georgio Strano and Paolo Galluzzi who came in as partners in the project agreed to pull out the telescope — which never happens; this telescope always stays in the case. They dusted it off and we shot it with every angle we could. As Georgio was going to put it back in the case, he turned to me and asked, “Would you like to look through it?” So we all got to look through it. That was a very emotional moment. I still tear up, just talking about it.
Then we shot our reenactments of Galileo in his home, and one of scenes you see is in his cellar where he recanted. Stefano Lecci, who is our actor, is the staff actor for the museum. Even though we held a city wide Galileo search, he walked in early in the morning and said, “Why are you doing a contest? I’m the guy.” And I thought, well, we’ll see. At the end of the day, I said, “You’re right. Why did we hold a contest?” He’s a great guy, and he knows the recantation by heart, and he did it in Italian. That was another very moving moment. He’s both the old and young Galileo. We had a great makeup artist. We shot old Galileo first, then middle aged Galileo, then the younger. Each time, the transition was remarkable.
We did a reenactment at Middleburg, with Copernicus, reenactments with Hans Lipperhey in Holland, and Christina Huygens. Old castles that date back the 1300’s are a very cool environment to shoot in! We had a lot of fun in Cambridge, shooting reenactments of Isaac Newton on campus, and we have him in the river, too. We have expert on Newton speaking and we pan the camera and there’s Newton rowing a punt.
Another memorable moment was being up at Mauna Kea shooting time lapse video. The laser at the Keck Telescope came on and we captured that, and we now have in our footage for our production. It was totally unplanned. It must have been 15 degrees below zero, but I just stood there. Normally I start the camera and leave, but I just stood there and watched it because it was just an amazing sight. There are always great things like that. You go out and you plan, and you know the shots you want of dome openings and telescopes turning and you want to shoot every telescope you can, but sometimes the unplanned things end up the best. The WM Keck Telescope. Credit: APOD
We ran 6 hours of tape through a camera a day. Just as astronomy is weather dependent, so too is shooting, and the light has to be there. We had some exceptional days for lighting, which created some very pretty shots.
Once, we were in a meeting with our senior reviewer at PBS, we were talking about timetables and technical issues, but they said, “We have to stop and tell you that the footage is exceptionally pretty.” I think that’s only because of the crew. Our Associate Producer Anita Ingrao and the Director of Photographer Scott Stender were phenomenal. I’ve been around observatories my whole life; I love them, and I can look at something and say, ‘that’s the shot,’ but putting someone else in there and having them see what I was seeing isn’t always the easiest thing to do. But they put faith in what I was seeing.
UT: How many people worked on the project?
Koenig: It depends on what day it is! We had a phenomenal crew. We have animators at the University of California at Chico, animators at Mirage 3 D, New Edge Studios in Atlanta, and more animators to create the planetarium shows. Anita and Scott and I mentioned did the production team in the field, Krista Shelby is an intern, and excellent audio operator. We have an excellent board of advisers that are all leaders and experts in their fields, as well as great individuals and supporters. Neil de Grasse Tyson is the narrator and we were very happy when joined the team. I think we’ve got everyone we could possibly have on the team. It’s a great project.
Everyone in the company is an astronomer or have a passion for astronomy. That’s one thing that makes us unique in this production. Everybody is into it, they understand the importance of it and have the spirit to go behind that. I think that’s what’s going to make our production stand out. We know that there are other folks doing productions for the International Year of Astronomy, but I think what will be the point of difference is that we look at the subject as astronomers and want to communicate it properly.
Click here for a list of credits for 400 Years of the Telescope.
Vulcanologists classify volcanoes into three groups: active, dormant and extinct. A dormant volcano is one that isn’t currently active or erupting, but geologists think that it’s still capable of erupting.
One of the best examples of a dormant volcano is Mauna Kea, one of the five volcanoes that make up the Big Island of Hawaii. The peak of Mauna Kea is 4,207 meters above sea level, but 10,203 meters above the base of the floor of the Pacific Ocean. Geologists classify Mauna Kea in the post-shield stage of volcanic evolution. It stopped being a shield volcano about 200,000 years ago. Mauna Kea’s last eruption is thought to be 2460 BC.
Volcanoes become dormant because the Earth’s plates are constantly shifting above volcanic hotspots. Each time the hotspot reaches the surface, it creates a new volcano. The tectonic plate continues to shift above the hotspot, and eventually the volcano is shut off from the magma chamber beneath. And so the magma finds a new source to the surface, creating a new active volcano. The older volcano stops erupting and becomes dormant. Here’s more information on the active volcanoes in the world.
Dormant volcanoes do still erupt from time to time, however, sometimes with devastating results for people who thought the volcano was completely extinct.
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Many volcanoes start out on land, rising above the surrounding landscape. But many more volcanoes get their start at the bottom of the ocean. These underwater volcanoes, or submarine volcanoes, can eventually grow into islands that rise above the surface of the ocean.
Geologists have identified more than 5,000 active underwater volcanoes, which account for more than 75% of the total lava that erupts every year. Most of these are located along the mid-ocean ridges, where the Earth’s tectonic plates are spreading apart. Most of these are very deep underwater, and difficult to study, but some are located in more shallow water.
An underwater volcano erupts differently than a surface volcano. This is because there is an unlimited amount of water to cool down the lava. A shell of rock hardens around the lava almost immediately, creating a type of formation called pillow lava. Deeper than about 2,000 meters, the pressure of the water is so high that it can’t boil, and so underwater volcanoes are difficult to find using hydrophones.
Underwater volcanoes build up over time, and can eventually reach the surface of the ocean. This is what happened to form the Hawaiian islands. The Earth’s crust has drifted above an active vent, creating each of the islands in turn. A new Hawaiian island, Lo’ihi, is forming under the ocean about 48 km off the southeast coast of Hawaii. It’s already taller than Mount St. Helens and will breech the surface in a few hundred thousand years.
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When you think of volcanoes, you immediately think of lava flows. These are the familiar rivers of lava pouring down the sides of the volcano, burning everything in their path, covering up building and generally ruining things. Well, you might be surprised to know that lava flows are the least hazardous way a volcano can kill you.
Molten rock is much thicker than a liquid like water. Even lava flows with the least viscosity (the least thick), will only flow at a maximum speed of a few kilometers per hour. You can easily out run a lava flow, and that’s why people are rarely killed by them. Building and trees, which are stuck to the ground, aren’t so lucky.
How far the lava flow goes depends on its viscosity. Lava flows made of basalt, like you might find in Hawaii, have very low viscosity, and so they can flow as much as 4 km away from the source and have a thickness of 10 meters. Thicker lava flows only get about 1 kilometer away from the source, but can be as thick as 100 meters.
People aren’t really at risk from lava flows, but they can do a tremendous amount of property damage. If the intense heat doesn’t set your house on fire, the slow moving wall of liquid rock will certainly knock it over and crush it to pieces. Entire towns built close to volcanoes have been overrun by lava flows, destroying houses and cars, encasing everything in meters of rock. Once an eruption is over, the lava flow can take days or even years to cool down.
Engineers have tried to battle nature, coming up with all kinds of ways to stop lava flows – few successful. In Italy, engineers have installed retaining walls to try and slow down lava flows coming down the side of Mount Etna, on the island of Sicily. These walls did slow down the lava flows enough that they didn’t reach inhabited land. In Hawaii, engineers bombed narrow lava tubes, forcing the lava to lose energy. And in Iceland, firefighters sprayed water on lava flows for nearly 5 months, cooling it so that it solidified early and didn’t block an important port.
We have written many articles about volcanoes for Universe Today. Here’s an article about the tallest volcano on Earth, and here’s an article about types of lava.
2005ke, a Type 1a supernova. Credit: NASA/Swift/S. Immler
Type 1a supernovae like 2005ke, above, are known to go off when one member of a star pair exceeds critical mass and kickstarts a runaway fusion reaction.
Researchers have long puzzled over why some of the explosions happen so fast. Now, a team of Chinese astronomers believes they’ve arrived at a probable cause for the earliest of the blasts.
A team of astronomers, led by Bo Wang from the Yunnan Observatory of the Chinese Academy of Sciences, have shown how the transfer of material from a ‘helium star’ to a compact white dwarf companion causes these cataclysmic events to take place. The new results appear in Monthly Notices of the Royal Astronomical Society.
Most type Ia supernovae are believed to occur when a white dwarf (the superdense remnant that is the end state of stars like the Sun) draws matter from a companion star orbiting close by. Previous theories for the origins of a Type Ia include an explosion of a white dwarf in orbit around another white dwarf, or an explosion of a white dwarf in orbit around a red giant star.
When the white dwarf mass exceeds the so-called Chandrasekhar limit of 1.4 times the mass of the Sun, it eventually collapses and within a few seconds undergoes a runaway nuclear fusion reaction, exploding and releasing a vast amount of energy as a type Ia supernova. Due to their high and remarkably consistent luminosities, astronomers use these events as ‘distance indicators’ to measure the distances to other galaxies and constrain our ideas about the Universe.
Scientists have confirmed more and more type Ia supernovae, and found that about half of them explode less than 100 million years after their host galaxy’s main star formation period. But previous models for these systems did not predict that they could be this young — so Wang and his team set out to solve the mystery.
Employing a stellar evolution computer code, they performed calculations for about 2600 binary systems consisting of a white dwarf and a helium star, a hot blue star which has a spectrum dominated by emission from helium. They found that if the gravitational field of the white dwarf pulls material from a helium star and increases its mass beyond the Chandrasekhar limit, it will explode as a type Ia supernova within 100 million years of its formation.
“Type Ia supernovae are a key tool to determine the scale of the Universe so we need to be sure of their properties,” said research team member Zhanwen Han, also from the Yunnan Observatory. “Our work shows that they can take place early on in the life of the galaxy they reside in.”
The team now plans to model the properties of the companion helium stars at the moment of the supernova explosions, which could be verified by future observations from the Large sky Area Multi-Object fiber Spectral Telescope (LAMOST).
LEAD IMAGE CAPTION: Supernova 2005ke shown in optical, ultraviolet and X-ray wavelengths. When it was captured, this was the first X-ray image of a Type 1a, and it provided observational evidence that Type Ia come from the explosion of a white dwarf orbiting a red giant star. Credit: NASA/Swift/S. Immler
Scientists have found a way to look past Earth’s atmosphere — and ancient cosmic dust — to glimpse galaxies that were formed in the first 5 billion years of the Universe.
A new study, released today in the journal Nature, reveals first-ever news from star-forming regions both near and far — including some from the edges of the Universe, which are racing away from us the fastest because of the Universe’s expansion.
The findings also clear up the sources of the Far Infrared Background, long shrouded in mystery.
The discoveries hail from the Balloon-borne Large Aperture Submillimetre Telescope (BLAST), which floated 120,000 feet (36,576 meters) above Antarctica in 2006.
The BLAST team chose to map a particular region of the sky called the Great Observatories Origins Deep Survey–South (GOODS-South), which was studied at other wavelengths by NASA’s three “great observatories” — the Hubble, Spitzer, and Chandra space telescopes. In one epic 11-day balloon flight, BLAST found more than 10 times the total number of submillimeter starburst galaxies detected in a decade of ground-based observations.
“We measured everything, from thousands of small clouds in our own galaxy undergoing star formation to galaxies in the Universe when it was only a quarter of its present age,” said lead author Mark Devlin, from the University of Pennsylvania.
In the 1980s and 1990s, certain galaxies called Ultraluminous InfraRed Galaxies were found to be birthing hundreds of times more stars than our own local galaxies. These “starburst” galaxies, 7-10 billion light years away, were thought to make up the Far Infrared Background discovered by the COBE satellite. Since the initial measurement of this background radiation, higher-resolution experiments have tried to detect the individual galaxies that comprise it.
The BLAST study combines telescope survey measurements at wavelengths below 1 millimeter with data at much shorter infrared wavelengths from the Spitzer Space Telescope. The results confirm that all the Far Infrared Background comes from individual distant galaxies, essentially solving a decade-old question of the radiation’s origin.
Star formation takes place in clouds composed of hydrogen gas and a small amount of dust. The dust absorbs the starlight from young, hot stars, heating the clouds to roughly 30 degrees above absolute zero (or 30 Kelvin). The light is re-emitted at much longer infrared and submillimeter wavelengths.
Thus, as much as 50 percent of the Universe’s light energy is infrared light from young, forming galaxies. In fact, there is as much energy in the Far Infrared Background as there is in the total optical light emitted by stars and galaxies in the Universe. Familiar optical images of the night sky are missing half of the picture describing the cosmic history of star formation, the authors say.
“BLAST has given us a new view of the Universe,” said Barth Netterfield of the University of Toronto, the Canadian principal investigator for BLAST, “enabling the BLAST team to make discoveries in topics ranging from the formation of stars to the evolution of distant Galaxies.”
In an accompanying News & Views piece, author Ian Smail, a computational cosmologist from Durham University in the UK, wrote that “the implication of these observations is that the active growth phase of most galaxies that are seen today is well behind them — they are declining into their equivalent of middle age.”
He also pointed out that studies of these extreme star-forming events in the early Universe will be aided by three major advances due over the next year or so: the submillimeter camera on the ESA/NASA Herschel Space Observatory; the development of large-format detectors working at submillimeter wavelengths, including one mounted on the James Clerk Maxwell Telescope; and the first phase of the Atacama Large Millimeter Array (ALMA).
“Such observations will allow astronomers to study the distribution of gas and star formation within these early galaxies,” Smail wrote, “which in turn will help to identify the physical process that triggers these ultraluminous bursts of star formation and their role in the formation of the galaxies we see in the Universe today.”
LEAD IMAGE CAPTION: The BLAST telescope just before launch in Antarctica. BLAST is in the foreground, next the 28 million cubic foot balloon, in the background is the volcano Mount Erebus. Credit: Mark Halpern
Source: Nature and a University of Pennsylvania press release (not yet online). Images, photographs, sky maps and the complete study are available at the BLAST Web site.
ESA’s space-borne X-ray observatory, XMM-Newton, has carried out an exclusive, 50-plus-hour observation of the starburst galaxy Messier 82, for the ‘100 Hours of Astronomy’ cornerstone project for the International Year of Astronomy 2009.
This first image shows bright knots in the plane of the galaxy, indicating a region of intense star formation, and emerging plumes of supergalactic winds glowing in X-rays.
XMM-Newton has been studying the sky in X-ray, optical and ultraviolet wavelengths simultaneously, since its launch in December 1999.
Messier 82 has several names including: M82, the Cigar Galaxy and NGC 3034. Located in the constellation Ursa Major at a distance of about 12 million light-years, it is the nearest and one of the most active starburst galaxies, meaning it shows an exceptionally high rate of star formation.
M82 is interacting gravitationally with its neighbour, the spiral galaxy Messier 81, which is probably the cause for the violent starburst activity in the region around its center.
This second image of Messier 82, compiled from observations in the optical and infrared, shows the very bright starry disc of the galaxy with striking dust lanes.
Source: ESA. More images, including a downloadable poster, are here. 100 Hours of Astronomy ended on Sunday, but the website still has loads of fun information. The International Year of Astronomy 2009 celebration is, of course, ongoing!
An Australian doctoral researcher using a backyard telescope has made a potentially big discovery: Earth’s oceans and continents shine differently on the dark side of the moon.
Now, Sally Langford, a doctoral candidate in physics at the University of Melbourne, is suggesting the “earthshine” of planets around other stars could provide long-distance windows into their surface features.
Langford's setup for moon observing. Credit: Stuart Wyithe, second author, also a physicist at the University of Melbourne.
Langford and her colleagues, from Melbourne as well as Princeton University, have shown for the first time that the difference in reflection of light from the Earth’s land masses and oceans can be seen on the dark side of the moon, a phenomenon known as earthshine. Their paper appears in this week’s edition of the international journal Astrobiology.
This is the first study in the world to use the reflection of the Earth to measure the effect of continents and oceans on the apparent brightness of a planet. Other studies have used a color spectrum and infrared sensors to identify vegetation, or for climate monitoring.
The researchers peered at the dark side of the crescent moon using a 20 cm (8 inch) telescope, on the bigger side of what most amateur astronomers use in their yards.
For three years, Langford took images of the Moon to measure the earth’s brightness as it rotated. Observations of the Moon were made from Mount Macedon in Victoria, for around three days each month when the Moon was rising or setting. The study was conducted so that in the evening, when the Moon was a waxing crescent, the reflected earthshine originated from Indian Ocean and Africa’s east coast. In the morning, when the Moon was a waning crescent, it originated only from the Pacific Ocean.
“When we observe earthshine from the Moon in the early evening we see the bright reflection from the Indian Ocean, then as the Earth rotates the continent of Africa blocks this reflection, and the Moon becomes darker,” Langford said.
Langford said the variation revealed the difference between the intense mirror-like reflections of the ocean compared to the dimmer land.
“In the future, astronomers hope to find planets like the Earth around other stars,” Langford said. “However these planets will be too small to allow an image to be made of their surface. We can use earthshine, together with our knowledge of the Earth’s surface, to help interpret the physical makeup of new planets.”
LEAD IMAGE CAPTION: Earthshine on a crescent moon. Credit: Edward W. Szczepanski, Houston Astronomical Society (click on the photo to visit Szczepanski’s page)
Source: University of Melbourne. The paper is available here.
The NASA/ESA Hubble Space Telescope captured this image of NGC 7049 in the constellation of Indus, in the southern sky. Credit: NASA, ESA and W. Harris (McMaster University, Ontario, Canada)
Credit: NASA, ESA and W. Harris (McMaster University, Ontario, Canada)
The Hubble Space Telescope has captured a new image of NGC 7049, a mysterious looking galaxy that blurs the boundary between spiral and elliptical galaxies.
This picture, taken with a small ground-based camera, shows on its central-left portion the constellation of Indus, in the southern sky. Credit: A. Fujii
NGC 7049 is found in the constellation of Indus, and is the brightest of a cluster of galaxies, a so-called Brightest Cluster Galaxy. They represent some of the oldest and most massive galaxies, and they allow astronomers to study the elusive globular clusters lurking within.
Globular clusters are very dense and compact groupings of a few hundreds of thousands of young stars bound together by gravity. The globular clusters in NGC 7049 are seen as the sprinkling of small faint points of light in the galaxy’s halo. The halo – the ghostly region of diffuse light surrounding the galaxy – comprises myriad individual stars and provides a luminous background to the remarkable swirling ring of dust lanes surrounding NGC 7049’s core. The dust lanes appear as a lacy ring.
The image was taken by the Advanced Camera for Surveys on Hubble, which is optimized to hunt for galaxies and galaxy clusters in the remote and ancient Universe, at a time when our cosmos was very young.
The constellation of Indus, or the Indian, is one of the least conspicuous in the southern sky. It was named in the 16th century by Dutch astronomer Petrus Plancius from observations made by Dutch navigator Pieter Dirkszoon Keyser and Dutch explorer Frederick de Houtman.
