Astronomy Archives

June 8, 2009December 24, 2015 by Fraser Cain

Volcano Lahar

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Volcanoes have many ways to kill you, from hot lava, rocks blasted through the air, to poisonous gasses. But one of the most dangerous parts of a volcano are mud flows that can stream down their sides, following the path of river valleys. Volcano lahars have been the cause of many deaths in the last few centuries. With more people living close to or even on the flanks of steep volcanoes, even more deaths are certain.

Lahars are volcanic mudflows, and they don’t have to come directly from volcanic activity. They occur when huge amounts of volcanic ash, mixed with water flows down the side of a mountain. They can flow at speeds more than 100 km/hour, following the path of a river valley, but with the weight of concrete. Lahars are liquid when they’re flowing, and then harden almost solid when they stop. One cause of a volcano lahar is an eruption, when volcanic ash mixes with a volcano glacier, creating this muddy mixture. It’s also possible for a lahar to form when a lake or dam breaks, mixing water with ash already on the side of a volcano.

And they’ve caused terrible damage. The eruption of Nevado del Ruiz in Columbia in 1985 sent lahars down the mountainside, burying the city of Armero under 5 meters of mud and debris. A lahar coming off Mount Rainier in Washington sent a wall of mud 140 meters deep, covering a total area of 330 square kilometers – 300,000 people now live in the area covered by that lahar. In the recent eruption of Mount Pinatubo in 1991, 700 people were killed by the lahars that came down the mountain after the intense rainfall that followed the eruption.

The term lahar comes from the Indonesian word for “wave”.

We have written many article about volcanoes in Universe Today. Here’s an article about pyroclastic flows, and here’s an article Plinian eruptions which can cause pyroclastic flows.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

June 8, 2009March 24, 2012 by Nancy Atkinson

Astronomers Find New Way to Measure Cosmic Distances

Cepheid stars in galaxies such as M81, shown here. The stars could offer a new way to measure distances to objects in the universe. Image courtesy of Ohio State University.” width=”580″ height=”535″ class=”size-medium wp-image-32187″ />

hio State University astronomers are using the Large Binocular Telescope to look for ultra long period cepheid stars in galaxies such as M81, shown here. The stars could offer a new way to measure distances to objects in the universe. Image courtesy of Ohio State University.

Using a rare type of giant Cepheid variable stars as cosmic milemarkers, astronomers have found a way to measure distances to objects three times farther away in space than previously possible. Classical Cepheids are stars that pulse in brightness and have long been used as reference points for measuring distances in the nearby Universe. But astronomers have found a way to use “ultra long period” (ULP) Cepheid variables as beacons to measure distances up to 300 million light years and beyond.
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June 5, 2009December 24, 2015 by Fraser Cain

Volcanoes in Mexico

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Mexico is known for its beaches and historical ruins, but did you know that Mexico has some of the most spectacular volcanoes in North America? It has the tallest volcano in North America (the third tallest mountain in North America), and islands formed from shield volcanoes.

Mexico Volcanoes

Barcena – a volcano on the island of San Benedicto that wiped out all life on the island in 1952.
Ceboruco – A volcano that had the largest eruption in Mexico in 930 AD.
Chichinautzin – A volcanic field just outside Mexico City.
Colima – An active volcano visible from Mexico City.
El Chichon – A previously unknown lava cone that erupted in 1982, killing 2000 people.
Jocotitlan Volcano – A distinct horseshoe-shaped volcano.
Nevado de Toluca – A dormant stratovolcano and Mexico’s 4th highest peak.
Paricutin – A volcano that appeared suddenly in a Mexican cornfield, rose to a height of more than 400 meters and then stopped growing.
Pico de Orizaba – A dormant volcano that hasn’t erupted since the 17th century, it’s the third tallest peak in North America.
Popocatepetl – An active volcano in Mexico, the 2nd tallest active volcano in North America.
San Martin – A shield volcano near the Gulf Coast of Mexico.
Socorro – a shield volcano that makes up the largest of the Revillagigedo Islands.
Tacana – A tall stratovolcano that straddles the border between Mexico and Guatemala

We have written many articles about volcanoes for Universe Today. Here’s an article about Costa Rica volcanoes, and here’s a full list of famous volcanoes around the world.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

June 5, 2009December 24, 2015 by Fraser Cain

Jocotitlan Volcano

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Jocotitlan is an stratovolcano located about 60 kilometers northwest of Mexico City. It rises to an elevation of 3,900 meters above sea level, but it’s isolated from any other mountains or peaks in the surrounding plains, rising up 1,300 meters above the Toluca basin.

One of its most prominent features is a horseshoe-shaped escarpment visible from the northeast; it formed when the northeast edge of the caldera collapsed. Whenever this event happened, it created an enormous landslide that buried 80 square kilometers of land to the northeast of the volcano.

Jocotitlan formed in the Pleistocene era (11,000 to 1.8 million years ago) primarily out of andesitic-to-dacitic lava flows. After that there was an obsidian dacitic eruptino and then the creation of a lava dome complex. The volcano produced regular lava flows, pumice-fall eruptions and pyroclastic surges. The last known eruption at Jocotitlan happened about 700 years ago, and produced block-and-ash flows and pyroclastic surges.

We have written many article about volcanoes for Universe Today. Here’s an article about other volcanoes in Mexico, and here’s an article about many famous volcanoes.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

June 5, 2009December 24, 2015 by Fraser Cain

Barcena Volcano

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Barcena is a volcano located on the island of San Benedicto, the third largest island of the Revillagigedo Islands. The whole island is only about 4.8 km by 2.4 km and Barcena takes up a good chunk of the southern end. Barcena rises to an elevation of 332 meters, forming a volcanic crater.

There has only been on eruption from Barcena in recorded history, but it was a big one. On August 1, 1952, Barcena had a severe Vulcanian eruption measuring 3 on the Volcanic Explosivity Index. It released huge pyroclastic flows that rolled over the entire island, covering it in ash and pumice to a depth of 3 meters. Within less than 2 weeks, it had created a new volcanic cone more than 300 meters high. A second series of eruptions started up later in the year, releasing magma that broke out of the cone and flowed into the ocean. By late 1953, the volcano went dormant again.

The eruption wiped out all the plants and wildlife on the island, making the San Benedicto Rock Wren extinct. Within a few years the plants and wildlife made a return, although the island still looks barren.

We have written many article about volcanoes for Universe Today. Here’s an article about Tacana, a tall stratovolcano that straddles the border between Mexico and Guatemala. And here’s an article about Paricutin, a volcano that suddenly appeared in a farmer’s cornfield.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

June 5, 2009December 24, 2015 by Fraser Cain

Colima Volcano

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Colima is the name of a state in Mexico, as well as a city. But we’re going to be talking about another feature in Mexico, Colima’s Volcano. Colima is the most active volcano in Mexico, having erupted more than 40 separate times since records were first kept in 1576. The volcano stands at an elevation of 4,330 meters.

Geologists believe that Colima has been active for about 5 million years. Back in the Pleistocene era (between 11,000 and 1.8 million years ago), a huge earthquake triggered a landslide on the volcano, releasing 25 cubic kilometers of debris that traveled 120 km, reaching the Pacific Ocean. Major collapse events like this are believed to happen every few thousand years.

In the Colima volcano complex there are actually two different volcanoes. The older, dormant volcano is known as Nevado de Colima, and it stands at an elevation of 4330 meters. The younger, active volcano is known as the Volcan de Colima – Colima Volcano.

Colima has the potential to be a devastating volcano. There are about 300,000 people living within 40 km of the volcano. It has been chosen by scientists as a “Decade volcano”, and has been singled out for careful study to predict if and when a major eruptive event is happening. There have been several evacuations of the region over the last decade, since a large eruption or lava flow could affect an 11-kilometer radius around the volcano. In a 1999 eruption, Colima blasted out material that reached a distance of 5 km. Fortunately, lava flows from the volcano have never reached inhabited areas.

We have written many articles about volcanoes for Universe Today. Here’s an article about Popocatepeti, another volcano in Mexico. And here’s an article about Paricutin, a volcano that appeared in a cornfield in Mexico.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

June 5, 2009December 24, 2015 by Fraser Cain

Popocatepetl Volcano

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Popocatepetl is a famous volcano. It is one of the most active volcanoes in Mexico, and the second tallest mountain in the country with an elevation of 5,426 meters (it’s the third tallest active volcano in the Northern Hemisphere). It’s located about 70 km southeast from Mexico City, so it can be seen on clear days from the city – especially when it’s erupting clouds of ash many km into the air. It has had more than 20 major eruptions since the arrival of the Spanish in 1519.

The name Popocatepetl comes from the Aztec word for smoking mountain. More than 30 million people live within view of the mountain, including Mexico City and the Pueblo, and hundreds of thousands would be at risk during a major eruption. Pyroclastic flows could endanger villages and towns built up on the volcano’s flanks, and although it has been relatively safe in the last century, it has had several plinian eruptions over the last 10,000 years.

The peak of Popocatepetl is clad is glaciers, and has a steep-walled 450-meter-deep crater at the top. From most vantages, the peak of the mountain looks very symmetrical; although, it does have a side peak called Ventorillo to the northwest. Geologists have determined that three previous major cones were destroyed during the Pleistocene era (between 11,000 and 1.8 million years ago).

Most of the eruptions on Popocatepetl have been mild-to-moderate Vulcanian steam and ash emissions, with some larger explosive eruptions in 1519 and 1663. In 1920, there were some explosive eruptions and a small lava plug at the crater at the top of the volcano. There have been some additional ash cloud events in the 1920s through the 1940s, but the volcano has been largely quiet since then.

We have written many articles about volcanoes for Universe Today. Here’s an article about Paricutin, a famous volcano in Mexico that appeared in a farmer’s cornfield. And here’s a list of famous volcanoes around the world.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

June 5, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast: June 5-7, 2009

Greetings, fellow SkyWatchers! Are you ready for another great weekend of observing? If you’re thinking that it’s going to be boring because there’s Moon, then think again. If you were paying attention, you’d have noticed that Venus and Mars rose together this morning only about five degrees apart. Need more reasons to get out? Try 13 of them as you challenge yourself to see how many craterlets you can resolve in the mighty Clavius. Stars more to your liking? Then have a look at the Theta Virginis system or beautiful red Omega. Celebrate the Strawberry Moon, locate R Hydrae or just be on hand for an occultation event… It’s all part of the weekend scene! Grab your telescopes or binoculars and I’ll see you in the backyard.

Friday, June 5, 2009 – If you were up early this morning, did you see Venus and Mars no more than 30 minutes before dawn? The pair was very low – only about 20 degrees above the horizon -and about 5 degrees apart.

Now, let’s take a look at John Couch Adams, a discoverer of Neptune who was born on this date in 1819. Said he:

‘‘. . .the beginning of this week of investigating, as soon as possible after taking my degree, the irregularities in the motion of Uranus. . .in order to find out whether they may be attributed to the action of an undiscovered planet beyond it.’’

But that’s not all Adams contributed! He was the first to associate the Leonid meteor shower with the orbital path of a comet, and he also observed the Moon.

As we begin observing Selene this evening, let’s have a look at awesome crater Clavius. As a huge mountain-walled plain, Clavius will appear near the terminator tonight in the lunar Southern Hemisphere, rivaled only in sheer size by similarly structured Deslandres and Baily. Rising 1,646 meters above the surface, the interior wall slopes gently downward for a distance of almost 24 kilometers and spans 225 kilometers. Its crater-strewn walls are over 56 kilometers thick! Clavius is punctuated by many pockmarks and craters; the largest on the southeast wall is named Rutherford. Its twin, Porter, lies to the northeast. Long noted as a test of optics, Clavius crater can offer up to 13 such small craters on a steady night at high power. How many can you see?

If you want to continue tests of resolution, why not visit nearby Theta Virginis (RA 13 09 56 Dec -05 32 20)? It might be close to the Moon, but it’s 415 light-years away from Earth! The primary star is a white A-type subgiant, but it’s also a spectroscopic binary comprising two companions that orbit each other about every 14 years. In turn, this pair is orbited by a 9th magnitude F-type star that is a close 7.1’’ away from the primary. Look for the fourth member of the Theta Virginis system, well away at 70’’ but shining at a feeble magnitude 10.4.

Saturday, June 6, 2009 – Today is all about lunar history! We begin with the 1932 birth on this date of David Scott, the seventh person to walk on the Moon and the first to ride the Lunar Rover on the surface during the Apollo 15 mission. Sharing his birth date, but almost 500 years earlier, was the astronomer Regiomontanus (1436). Regiomontanus made observations of a comet, which were accurate enough to associate it with Comet Halley 210 years later, and his interest in the motion of the Moon led him to make the important observation that lunar distances could be used to determine longitude at sea! Let’s head to the Moon. . .

Although at first glance tonight crater Copernicus will try to steal the scene, head further south to capture another Lunar Club Challenge – Bullialdus. Even binoculars can make out this crater with ease near the center of Mare Nubium. If you’re scoping, power up – this one is fun! Very similar to Copernicus, note Bullialdus’ thick, terraced walls and central peak. If you examine the area around it carefully, you can note it is a much newer crater than shallow Lubiniezsky to its north and almost non-existent Kies to the south. On Bullialdus’ southern flank, it’s easy to make out itsA and B craters, as well as the interesting little Koenig to the southwest. Although it will be a bit overlit, if you head to the southeast shore of Mare Humorum, you can spot crater Regiomontanus as well. It’s just south of Purbach.

Now let’s starhop four finger-widths northwest of Beta Virginis for another unusual star – Omega (RA 11 38 27 Dec +08 08 03). Classed as an M-type red giant, this 480 light-year-distant beauty is also an irregular variable that fluxes by about half a magnitude. Although you won’t notice much change in this 5th magnitude star, it has a very pretty red coloration and is worth the time to view.

Sunday, June 7, 2009 – Today we celebrate the birth of Bernard Burke, co-discoverer of radio waves emitted from Jupiter. Listening to Jupiter’s radio signals is a wonderful hobby that can be practiced by anyone with enough room to set up a dipole antenna. If you’d like more information—or want to hear a recording of Jupiter yourself—visit Radio JOVE on the web! Tonight is Full Strawberry Moon, a name used by every Algonquin tribe in North America because the short season for harvesting the tasty red fruit comes each year during the month of June!

Tonight let’s have a look at a tasty red star – R Hydrae (RA 13 29 42 Dec -23 16 52) located a fist-width south of Spica. R Hydrae was the third long-term variable star discovered and was credited to Maraldi in 1704. Although Hevelius observed it 42 years earlier, it wasn’t recognized as variable because its changes happen over more than a year. At maximum, R reaches near 4th magnitude, but drops well below naked-eye perception to magnitude 10. During Maraldi’s and Hevelius’s time, this incredible star took over 500 days to cycle, but it has speeded up to around 390 days in the present century.

Why such a wide range? Scientists aren’t really sure. R Hydrae is a pulsing M-type giant whose evolution may be progressing more rapidly than expected due to changes in structure. What we do know is that it’s around 325 light-years away and approaching us at 10 kilometers per second! To the telescope, R will have a pronounced red coloration, which deepens near minimum. Nearby is 12th magnitude visual companion star Ho 381, which was first measured for angle position and distance in 1891. Since then, no changes in separation have been noted, leading us to believe the pair may be a true binary.

Now watch as the Moon devours a red star! Brilliant Antares will be less than a half degree away from the limb for most observers and will be occulted for some lucky others! Be sure to check the IOTA website for exact times and locations and enjoy!

Until next week? Ask for the Moon, but keep on reach for the stars!

This week’s awesome images are (in order of appearance): Clavius (credit—Wes Higgins), Theta Virginis (credit—Palomar Observatory, courtesy of Caltech), Bullialdus (credit—Wes Higgins), Omega Virginis (credit—Palomar Observatory, courtesy of Caltech), Nearside of the Moon as imaged by Apollo 11 (credit—NASA) and R Hydrae (credit—Palomar Observatory, courtesy of Caltech). We thank you so much!

June 4, 2009December 24, 2015 by Fraser Cain

Soufriere Hills

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The Soufriere Hills volcano is an active complex stratovolcano on the Caribbean island of Montserrat. It was dormant for many years, but returned to activity in 1995 with a series of eruptions that forced the evacuation of 2/3rds of the entire island. The volcano has been continuously erupting, and has now destroyed about half the surface of the island, including the airport.

Soufriere Hills is a typical subduction volcano, created by the subduction of the Atlantic Plate underneath the Caribbean Plate. The largely andesitic volcano takes up the southern half of the island of Montserrat, rising to an elevation of 1050 meters. The summit area consists of a series of lava domes. One of the largest is English crater, measuring about 1 km across, which formed about 4,000 years ago when the summit collapsed. Previous to the 1995 eruption, Soufriere Hills was largely silent; there was an eruption in the 17th century that produced the Castle Peak lava dome.

And so, the eruption that began on July 18, 1995 was the first to hit the volcano since the 17th century. But then it started to erupt regularly with pyroclastic flows and mudflows. An eruption on June 25 killed 19 people, and completely destroyed the island’s airport. Needless to say, the island’s tourist industry was completely wiped out, and most of the inhabitants were evacuated away from the island.

Soufriere Hills is continuing to erupt regularly. A devastating eruption occurred on July 2008 without any warning, shooting out pyroclastic flows that reached the capital city of Plymouth. An ash column rose up into the air to an altitude of 12 km.

We have written many articles about volcanoes for Universe Today. Here’s an article about Mount Pelee that killed 30,000 people on the island of Martinique, and here’s an article about other famous volcanoes.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

June 4, 2009December 24, 2015 by Nancy Atkinson

No Nature VS. Nurture for Stars

The Arches Cluster, with young, massive stars, taken by the NACO on ESO’s Very Large Telescope.

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Stars don’t seem to mind where they grow up. Either in a nice quiet neighborhood or in the hellish environment near a supermassive black hole, astronomers were surprised to find the same proportions of low- and high-mass young stars in different types of star forming regions. Using the Very Large Telescope, astronomers snapped one of the sharpest views ever of the Arches Cluster — an extraordinary dense cluster of young stars near the supermassive black hole at the center of the Milky Way. “With the extreme conditions in the Arches Cluster, one might indeed imagine that stars won’t form in the same way as in our quiet solar neighbourhood,” says Pablo Espinoza, the lead author of the paper reporting the new results. “However, our new observations showed that the masses of stars in this cluster actually do follow the same universal law”.

The massive Arches Cluster is located 25 000 light-years away towards the constellation of Sagittarius. It contains about a thousand young, massive stars, less than 2.5 million years old. Astronomers say this region is an ideal laboratory to study how massive stars are born in extreme conditions, as the stars in the cluster experience huge opposing forces from all the activity going on near the supermassive black hole. The Arches Cluster is also ten times heavier than typical young star clusters scattered throughout our Milky Way and is enriched with chemical elements heavier than helium.

The Arches Cluster is located in the centre of the image, but its stars are hidden behind large amount of dust. The bright star at the top of the image is 3 Sagittarii, while the cluster of stars seen at the bottom left is NGC 6451. Credit: Digitized Sky Survey

Using the NACO adaptive optics on the VLT, astronomers were able to take the clearest images yet of the Arches Cluster. Observing the Arches Cluster is very challenging because of the huge quantities of light-absorbing dust between Earth and the Galactic Centre, which visible light cannot penetrate. This is why NACO was used to observe the region in near-infrared light.

The new study confirms the Arches Cluster to be the densest cluster of massive young stars known. It is about three light-years across with more than a thousand stars packed into each cubic light-year — an extreme density a million times greater than in the Sun’s neighborhood.
Astronomers studying clusters of stars have found that higher mass stars are rarer than their less massive brethren, and their relative numbers are the same everywhere, following a universal law.

The astronomers were also able to study the brightest stars in the cluster. “The most massive star we found has a mass of about 120 times that of the Sun,” says co-author Fernando Selman. “We conclude from this that if stars more massive than 130 solar masses exist, they must live for less than 2.5 million years and end their lives without exploding as supernovae, as massive stars usually do.”

The total mass of the cluster seems to be about 30,000 times that of the Sun, much more than was previously thought. “That we can see so much more is due to the exquisite NACO images,” says co-author Jorge Melnick.

Read the team’s paper.

Source: ESO