Spiral galaxies get their name because of their beautiful spiral shape and iconic arms. But why do galaxies have these spiral shapes, and what causes the arms?
Galaxies are some of the most beautiful and inspiring structures in the Universe. As you know, they aren’t solid disks, they’re a gigantic spill of individual stars webbed together by gravity. There are a few rough fundamental shapes that a galaxy can have, and the bulk of these are some variation of a spiral. Each one with twisting arms of stars reaching tens of thousands of light years in every direction along a plane, out from a galactic core.
So what gives them this characteristic spiral shape? Earliest galaxies didn’t have clearly defined spiral arms. They were either two-armed or, had thick irregular chaotic woolly arms with star forming clumps. After 3.6 billion years, however, the chaos had settled down into the shapes we see today. But it took until the Universe was 8 billion years old for these modern multi-armed spirals, like the Milky Way or Andromeda to appear.
So where did they come from? These arms are in fact density waves passing through the galaxy, with stars moving in and out of the waves. The arms themselves aren’t permanent structures made of the same clumps of stars.
Imagine driving down a highway and people are slowing down to gape slack-jawed a crashed alien saucer. Cars will slow down as they reach the saucer and form a clump, and then the car in the lead of the clump will accelerate and proceed down the highway as other cars progress through the clump to take their place.
This is a great analogy for movement in a galaxy. As a density wave approaches, stars accelerate towards it. Then they slow down as they move away from it. Just like a comet falling into the gravity well of the Sun. And when the density wave moves through an area, it kicks off an era of star formation. So the material of the galaxy is being constantly stirred and new stars are born as a density wave makes its way through the galaxy.
Six spectacular spiral galaxies are seen in a clear new light in images from ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. Credit: ESO
When you picture this, keep in mind that stars closer to the core of the galaxy orbit faster than the spiral arm, and the stars further out go more slowly. Our galaxy, the Milky Way takes about 240 million years to complete a full rotation. But we pass through a major spiral arm every 100 million years or so, remaining in the higher density region for about 10 million years. Astronomers have only recently figured out why these arms exist in the first place.
Originally, they suspected it might be like a garden sprinkler, with material fountaining out from the center of the galaxy, or channeled by magnetic fields. They also thought that the arms might be transient features. Appearing and disappearing over time. But new evidence and simulations show they’re long lasting, they believe the arms themselves form as a result of giant molecular clouds of hydrogen. These clouds initiate the arms and keep the shape sustained over billions of years.
What do you think? What’s your favorite spiral galaxy? Tell us in the comments below.
Frame from the Rosetta Mission simulation shows the probe and comet when closest to the sun in late 2015. Credit: INOVE
Hang onto your space helmets. With a few moves of the mouse, you can now follow the European Rosetta mission to its target comet with this interactive 3-D simulator. Go ahead and give it a click – it’s live! The new simulator was created by INOVE Space Models, the same group that gave us the 3-D solar system and Comet ISON interactive models.
The embedded version gives you a taste, so be sure to also check out the full-screen version. You can either click play to watch the mission from start to finish or you can drop it at key points by selecting from list of 11 highlights on the left side of your screen. A tick-tock at the bottom of the screen helps reference the time and what the spacecraft is doing at that moment in the video.
To interact with the model, simply click the screen. The action stops, allowing you to zoom in and out by scrolling; to change orbital viewpoints hold down the mouse button and drag. So easy!
Simulator view of Rosetta’s first Earth flyby / gravity assist in March 2005. The probe flew by Earth three times and Mars once to conserve fuel and send it beyond the asteroid belt to rendezvous with Comet Churyumov-Gerasimenko. Credit: INOVE
I like the realism of the simulation, the attention paid to the planets’ variable spin rates and orbital periods and how well model illustrates the complicated maneuvers required to “fling” the probe to Comet Churyumov-Gerasimenko. And I do mean fling. Watching the video from a face-on solar system perspective I was struck by how Rosetta’s flight path resembled a spiral after repeated gravity assists by Mars and Earth.
Rosetta heads toward Comet C-G after its final Earth flyby in this face-on view. Credit: INOVE
Whether you’re a teacher or an armchair space enthusiast looking for an easy-to-understand, graphic way to find out how Rosetta will meet its target, I doubt you’ll find a more effective tool.
A grouping of galaxies, known as J0717 (center) is visible in this Spitzer Space Telescope image. Credit: NASA/JPL-Caltech/P. Capak (Caltech)
Talk about turning back time. Three NASA observatories — the Hubble Space Telescope, the Chandra X-Ray Observatory and the Spitzer Space Telescope — are all working together to look for the universe’s first galaxies. The project is called “Frontier Fields” and aims to examine these galaxies through a technique called gravitational lensing, which allows astronomers to peer at more distant objects when massive objects in front bend their light.
“Our overall science goal with the Frontier Fields is to understand how the first galaxies in the universe assembled,” stated Peter Capak, a research scientist with the NASA/JPL Spitzer Science Center at the California Institute of Technology and the Spitzer lead for the Frontier Fields.
“This pursuit is made possible by how massive galaxy clusters warp space around them, kind of like when you look through the bottom of a wine glass.”
Using the three observatories allows investigators to peer at the galaxies in different light wavelengths (namely, infrared for Spitzer, shorter infrared and optical for Hubble, and X-rays for Chandra). The teams also plan to learn more about how the foreground clusters influence the “warping” of the galaxies behind.
The Hubble and Spitzer telescopes are designed to locate where the galaxies are (and if they are indeed early galaxies) while Chandra can map out the X-ray emissions to better determine the galaxies’ masses. An early example of this project at work was examination of Abell 2744, which yielded a distant find: Abell2744 Y1, one of the earliest known galaxies, which was born about 650 million years after the Big Bang.
Expedition 38 crew members proudly sport their national flags in this March 2014 picture from the International Space Station. Pictured (clockwise from top center) are Russian cosmonaut Oleg Kotov, commander; Japan Aerospace Exploration Agency astronaut Koichi Wakata, Russian cosmonaut Sergey Ryazanskiy, NASA astronauts Rick Mastracchio and Mike Hopkins, and Russian cosmonaut Mikhail Tyurin, all flight engineers. Credit: NASA
NASA plans to cease most work with the Russian Federal Space Agency amid growing tensions concerning the Ukrainian crisis, a spokesperson confirmed with a statement to Universe Today Wednesday evening (April 2).
While the International Space Station will still see work to “maintain safe and continuous operation”, most other NASA activities with Roscosmos will cease, the statement read. It added (citing the Obama administration) that Congress now faces a choice between fully funding human U.S. launches again in 2017, or facing years more of sending money to the Russians for Soyuz launches from Kazakhstan.
In full, this is the statement that Bob Jacobs, NASA’s deputy associate administrator of communications, sent to Universe Today (UPDATE, 8:54 p.m. EDT — this is also now available on NASA’s G+ page)
Given Russia’s ongoing violation of Ukraine’s sovereignty and territorial integrity, NASA is suspending the majority of its ongoing engagements with the Russian Federation. NASA and Roscosmos will, however, continue to work together to maintain safe and continuous operation of the International Space Station.
NASA is laser focused on a plan to return human spaceflight launches to American soil, and end our reliance on Russia to get into space. This has been a top priority of the Obama Administration’s for the past five years, and had our plan been fully funded, we would have returned American human spaceflight launches – and the jobs they support – back to the United States next year.
With the reduced level of funding approved by Congress, we’re now looking at launching from U.S. soil in 2017. The choice here is between fully funding the plan to bring space launches back to America or continuing to send millions of dollars to the Russians. It’s that simple. The Obama Administration chooses to invest in America – and we are hopeful that Congress will do the same.
It is unclear from this statement exactly what activities would constitute “safe and continuous operation” of station. So, for example, it’s unclear so far if (for example) NASA will still send photographers to cover launches and landing in Russia, or to what extent NASA TV broadcasts of Russian spacewalks would be affected.
Since the shuttle retired in 2011, NASA and other space agencies such as the European Space Agency have relied on Russian Soyuz spacecraft to bring astronauts to the International Space Station. Crews are generally made up of large proportions of Russian cosmonauts and American astronauts, as well as a few astronauts from other agencies. The current Expedition 39 crew has has three Russians, two Americans and a Japanese commander, Koichi Wakata. Expedition 40 will launch aboard a Soyuz spacecraft in May, if all goes to plan.
The crew members of Expedition 40/41 pose in front of a Soyuz spacecraft simulator in Star City, Russia. From left, Alex Gerst (European Space Agency), Max Suraev (Roscosmos) and Reid Wiseman (NASA). Credit: NASA
The human spaceflight relationship between NASA and Russia stretches back to the 1970s when Russia was then the Soviet Union. Their first joint mission was with the Apollo-Soyuz Test Project in 1975. That relationship expanded when several NASA shuttles visited the Russian space station Mir in the 1990s, laying the groundwork for the International Space Station agreement today.
NASA is working on a commercial crew program that right now is slated to bring U.S. astronauts into space from American soil again in 2017. There are several proposals being considered: a human-rated version of SpaceX’s Dragon, Blue Origin’s New Shepard, Sierra Nevada Corp.’s Dream Chaser and the Boeing Co.’s CST-100. NASA releases regular updates on how these companies — most of which receive money from the agency for development — are progressing, with the most recent update coming March 31.
It is unclear, however, how much money CCP will receive in the upcoming fiscal 2015 budget request before Congress. Historically, NASA receives less money for this program than what the agency requests (which has pushed back launches by a few years). The new tensions with Russia, however, could make things different this time around. This seems to be what NASA is counting on in the statement.
As far as what missions could be affected due to cooperation with Russia, planetary scientist Barbara Cohen said on Twitter that while it may appear the US may do little with Russia beyond the International Space Station, cooperation in planetary science is rather big. Russian scientists contribute to several ongoing and upcoming NASA robotic missions, and US scientists are contributing to the planning for ExoMars, which is an ESA-Roscosmos mission, and the US is contributing Elektra telecommunication radios to the orbiter and part of a mass spectrometer for the rover. Additionally, US scientists are working with the Verera-D mission, a strategic Venus mission sponsored by Roscosmos, with participation by NASA’s Planetary Science Division.
The news of the breach comes about a month after NASA administrator Charlie Bolden told reporters that the Russian diplomacy crisis, which erupted after troops went to Crimea a few weeks ago (to U.S. and other countries’ condemnation), would not affect Soyuz launches or other activities related to the space station.
Screenshot from NASA TV of the Soyuz TMA-09M spacecraft arriving at the International Space Station.
“Everything is nominal right now in our relationship with the Russians. We continue to monitor the situation,” said NASA administrator Charles Bolden in a conference call with reporters March 4, following the release of NASA’s preliminary budget request.
“The safety of our crews and our assets that has not changed. Safety is the No. 1 of NASA’s core values, so we are constantly doing contingency planning on the International Space Station for emergencies that might arise,” Bolden added, citing an emergency ammonia pump replacement in December as one such example.
“Those are the kinds of things we are always planning for, and in terms of the situation on the ground, we will go into contingency planning for that as the situation dictates. But right now, we don’t see any reason to do so,” he added.
International Space Station operations were recently extended to at least 2024, and NASA officials have pointed out that it and similar agreements have weathered other world crises.
Wednesday’s news first came to light in a reported internal memo posted on SpaceRef’s website that morning. Jacobs did not confirm or deny the memo’s authenticity in the e-mail to Universe Today.
Universe Today will issue updates as circumstances warrant.
Totality! A seen during the "December solstice eclipse" of 2010. Photo by author.
April the 15th: In the United States, it’s a date dreaded by many, as the date to file taxes – or beg for an extension – looms large. But this year, Tax Day gives lovers of the sky something to look forward to, as the first of four total lunar eclipses for 2014 and 2015 occurs on the night of April 14th/15th favoring North and South America.
The circumstances for the April 15th, 2014 eclipse. The top chart shows the path of the Moon through the umbra, and the bottom chart shows the visibility region (light to shaded areas) Click here for a technical description. Credit: Eclipse Predictions by Fred Espenak, NASA/GSFC.
This marks the first total lunar eclipse visible from since December 10th 2011, which was visible at moonset from North America, and marks the start of the first of two eclipse seasons for 2014. Totality will last 1 hour, 17 minutes and 48 seconds, and will be visible in its entirety from the central Atlantic westward to eastern Australia. Unlike a total solar eclipse, which occurs along a narrow track, a total lunar eclipse can be viewed by the entire moonward facing hemisphere of the Earth.
Tracing the umbra: a mosaic of the December 2010 eclipse. Photos by author.
The action begins at 4:37 Universal Time (UT)/12:37 AM EDT, when the Moon enters the western edge of the Earth’s shadow known as the penumbra. The Moon will be completely immersed in the penumbra by 5:58 UT/1:58 AM EDT, but don’t expect to see anything more than a faint tan shading that’s slightly darker on the Moon’s northeastern edge.
The real action begins moments later, as the Moon encounters the ragged edge of the umbra, or the inner core of the Earth’s shadow. When does the umbra first become apparent to you? Totality then begins at 7:06 UT/3:06 AM EDT and lasts until 8:24 UT/4:24 AM EDT, with mid-eclipse occurring just south of the center of the Earth’s shadow at 7:46 UT/3:46 AM EDT.
Finally, the eclipse ends as the Moon slides out of the penumbra at 10:37 UT/ 6:37 AM EDT. Michael Zeiler (@EclipseMaps) has complied a fine video guide to the eclipse:
This eclipse is also notable for being part of a series of four lunar eclipses in 2014 & 2015, known as a “tetrad.” NASA eclipse expert Fred Espenak notes that this series of eclipses is also notable in that all four are visible in part or in their entirety from the United States. We’re in a cycle of 9 sets of tetrads for the 21st century, which began with the first set in 2003. Before that, you have to go all the way back to the 16th century for the last set of eclipse tetrads!
The position of the Moon within the Earth’s umbra on the morning of April 15th at 4AM EDT/8UT. Credit: Starry Night Education software.
For saros buffs, the April 15th eclipse is Member 56 of 75 of saros 122, which began on August 14th 1022 A.D. and runs out until a final penumbral eclipse of the series on October 29th, 2338. There are only two total eclipses left in this particular saros, one in 2032 and 2050. If you caught the total lunar eclipse of April 4th, 1996, you saw the last lunar eclipse in this same saros series.
Lunar eclipses have turned up at some curious junctures in history. For example, a lunar eclipse preceded the fall of Constantinople in 1453. A 2004 lunar eclipse also fell on the night that the Red Sox won the World Series after an 86 year losing streak, though of course, lunar eclipses kept on occurring during those losing years as well. Christopher Columbus was known to evoke an eclipse on occasion to get him and his crew out of a jam, and also attempted to use a lunar eclipse to gauge his position at sea using a method first described by Ptolemy while studying the lunar eclipse of September 20th, 331 B.C.
A handful of stars in the +8th to +12th magnitude range will be occulted by the eclipsed Moon as well. Brad Timerson of the International Occultation Timing Association (IOTA) has put together a list, along with graze line prospects across the United States. The brightest star to be occulted by the eclipsed Moon is +5th magnitude 76 Virginis across western South America and Hawaii:
The occultation footprint of 76 Virginis during the April 15th lunar eclipse. Credit: Occult 4.0
Note that the bright star Spica will be only just over a degree from the eclipsed Moon, and Mars will also be nearby, just a week past its 2014 opposition. And to top it off, Saturn is just one constellation to the east in Libra!
During the partial phases of the eclipse, watch for the Moon to take on a “Pacman-like” appearance. The Earth’s umbra is just under three times the size of the Moon, and the Greek astronomer Aristarchus of Samos used this fact and a little geometry to gauge the distance to our natural satellite in the 3rd century B.C.
As totality approaches, expect the innermost rim of the Moon to take on a ruddy hue. This is the famous “combination of all the sunrises and sunsets” currently underway worldwide as light is bent through the Earth’s atmosphere into its shadow. It’s happening every night, and during the totality of a lunar eclipse is the only chance that we get to see it.
Looking to the southwest at 4 AM EDT from latitude 30 degrees north on the morning of April 15th. Credit: Stellarium.
You don’t need anything more sophisticated than the naked eye or “Mark 1 eyeball” to enjoy a lunar eclipse, though it’s fun to watch through binoculars or a low-power telescope field of view. One interesting project that has been ongoing is to conduct timings for the moment when the umbra contacts various craters on the Moon. It’s a curious mystery that the Earth’s shadow varies by a small (1%) but perceptible amount from one eclipse to the next, and efforts by amateur observers may go a long way towards solving this riddle.
Said color of the fully eclipsed Moon can vary considerably as well: the Danjon scale describes the appearance of the eclipsed Moon, from bright and coppery red (Danjon 4) to so dark as to almost be invisible (Danjon 0). This is a product of the amount of dust, volcanic ash and aerosols currently aloft in the Earth’s atmosphere. During the lunar eclipse of December 9th, 1992 the Moon nearly disappeared all together, due largely to the eruption of Mount Pinatubo the year prior.
A lunar eclipse also presents a chance to nab what’s known as a Selenelion. This occurs when the Sun and the totally eclipsed Moon appear above the local horizon at the same time. This is possible mainly because the Earth’s shadow is larger than the Moon, allowing it to linger a bit inside the umbra after sunrise or before sunset. Gaining some altitude is key to making this unusual observation. During the April 15th eclipse, selenelion sightings favor the Mid-Atlantic and Greenland where totality is underway at sunrise and eastern Australia, where the reverse is true at sunset.
Want to have a go at measuring the brightness or magnitude of the eclipsed Moon? Here’s a bizarre but fun way to do it: take a pair of binoculars and compare the pinpoint Moon during totality to the magnitude of a known star, such as Antares or Spica.
Note that to do this, you’ll first need to gauge the magnitude extinction of your particular binoculars: NASA’s got a table for that, or you could field test the method days prior on Venus, currently shining at a brilliant -4.2 in the dawn. Hey, what’s a $1,000 pair of image-stabilized binocs for?
And of course, weather prospects are the big question mark for the event. Mid-April weather for North America is notoriously fickle. We’ll be watching the Clear Sky Chart and Skippy Sky for prospects days before the eclipse.
Photography during an eclipse is fun and easy to do, and you’ll have the waxing gibbous Moon available to practice on days prior to event. Keep in mind, you’ll need to slow down those shutter speeds as the Moon enters into totality, we’re talking going down from 1/60th of a second down to ¼” pretty quickly. In the event of a truly dark eclipse, the Moon may vanish in the view finder all together. Don’t be afraid to step exposures up to the 1 to 4 second range in this instance, as you’ve got over an hour to experiment.
Our “eclipse hunting rig…” the DSLR is piggy-backed to shoot stills on the main scope, which will shoot video. Note that the “f/34 field stop” will most likely be removed! Photo by author
Thus far, only one webcast for the eclipse has surfaced, courtesy of the venerable Slooh. We’ll most likely be doing a follow up roundup of eclipse webcasts as they present themselves, as well as a look at prospects for things like a transit of the ISS in front of the eclipsed Moon and weather forecasts closer to show time.
And speaking of spacecraft, China’s Chang’e 3 lander and Yutu rover will have a fine view of a solar eclipse overhead from their Mare Imbrium vantage point, as will NASA’s LRO and LADEE orbiters overhead. In fact, NASA hinted last year that the April 15th eclipse might spell the end of LADEE entirely…
And thus marks the start of eclipse season one of two for 2014. Next up will be a curious non-central annular solar eclipse over Antarctica on April 29th, followed by another total lunar eclipse on October 8th, and a fourth and final partial solar eclipse of the year for North America of October 23rd.
Watch this space and follow us on Twitter as @Astroguyz, as we’ll be “all eclipses, all the time,” for April… no new taxes guaranteed!
Next up: Heard the one about the Blood Moon? Yeah, us too… join us as we debunk the latest lunacy surrounding the eclipse tetrad!
– Got pics of the lunar eclipse? Send ‘em in to Universe Today, as a post-eclipse photo round up is a very real possibility!
An airplane at about 2,400 meters above the ground passes in front of the Moon on its way to landing at the Charles de Gaulle Airport in Paris, France. Taken from about 70 km from Paris. Credit and copyright: Sebastien Lebrigand.
Stuff from Earth’s interior, combined with simulations, have one research team pinning down the Moon’s age to only 95 million years after the Solar System formed (which would make our closest satellite about 4.4 billion years old.)
The simulation involved replicating how the Earth and the other terrestrial planets (Mercury, Venus and Mars) grew from a protoplanetary disc surrounding the young Sun. After 259 simulations, the researchers uncovered a link between when a Mars-sized object smacked Earth (eventually forming the Moon) and how much material Earth gained after the crash.
“This correlation just jumped out of the simulations and held in each set of old simulations we looked at,” stated Seth Jacobson of the Observatory of Cote d’Azur in France, who led the study.
Buzz Aldrin’s bootprint on the surface of the moon during the Apollo 11 mission on July 20, 1969. Credit: NASA
Researchers are calling this a “geologic clock” that dates the Moon independently from the samples Apollo astronauts collected from the moon in the 1960s and 1970s, which were dated using radioactive decay of atomic nuclei. The Earth’s mass was estimated using previously published material examining how plentiful “siderophile” (iron-associated) elements were in Earth’s mantle.
The exact date, for the curious, puts the Moon’s formation at 95 ±32 million years after the solar system began. The measurement agrees with some, but not all, radioactive dating methods.
The researchers argue that this new understanding will help scientists figure out which of the radioactive dating methods are the most useful to figure out the Moon’s age, but it will be interesting to see what other teams think of that conclusion.
An image mosaic of ice breaking up in the Arctic Ocean's Canada Basin on March 28, 2014. Image taken by Operation IceBridge's Digital Mapping System. Credit: Digital Mapping System/NASA Ames
The Arctic melt season is averaging five days longer with each passing decade, a new study by NASA and the National Snow and Ice Data Center reveals. And with more ice-free days, the water (which is darker than the surrounding ice) is absorbing the sun’s heat and accelerating the process. This means the Arctic ice cap has shrank by as much as four feet.
The sobering news comes following a study of satellite data from 1979 to 2013. By the end of this century, scientists believe, there will be a fully melted Arctic Ocean during the entire summer. And the news also comes in the same week that the Intergovernmental Panel on Climate Change (IPCC) released its own report on global warming.
“The Arctic is warming and this is causing the melt season to last longer,” stated Julienne Stroeve, a senior scientist at NSIDC, Boulder and lead author of a new study. “The lengthening of the melt season is allowing for more of the sun’s energy to get stored in the ocean and increase ice melt during the summer, overall weakening the sea ice cover.”
The research further revealed that solar radiation absorption depends on when the melt season begins; this is particularly true since the sun rises higher during the spring, summer and fall than in the winter. It’s still hard to predict when things will melt or freeze, however, since this depends on weather.
“There is a trend for later freeze-up, but we can’t tell whether a particular year is going to have an earlier or later freeze-up,” Stroeve said. “There remains a lot of variability from year to year as to the exact timing of when the ice will reform, making it difficult for industry to plan when to stop operations in the Arctic.”
Data was collected with NASA’s (long deceased) Nimbus-7 Scanning Multichannel Microwave Radiometer and instruments aboard Defense Meteorological Satellite Program spacecraft.
“When ice and snow begin to melt, the presence of water causes spikes in the microwave radiation that the snow grains emit, which these sensors can detect,” NASA stated. “Once the melt season is in full force, the microwave emissivity of the ice and snow stabilizes, and it doesn’t change again until the onset of the freezing season causes another set of spikes.”
The research has been accepted for publication in Geophysical Research Letters.
NGC 1316 (left) and its smaller companion galaxy NGC 1317. Image taken with the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. Credit: ESO
Shining 60 million light-years away all serene-looking is NGC 1316 (left) and a smaller galaxy NGC 1317. This new picture from the European Southern Observatory’s La Silla Observatory in Chile, however, reveals “battle scars” of ancient fights, the observatory stated.
“Several clues in the structure of NGC 1316 reveal that its past was turbulent. For instance, it has some unusual dust lanes embedded within a much larger envelope of stars, and a population of unusually small globular star clusters. These suggest that it may have already swallowed a dust-rich spiral galaxy about three billion years ago,” the European Southern Observatory stated.
“Also seen around the galaxy are very faint tidal tails — wisps and shells of stars that have been torn from their original locations and flung into intergalactic space. These features are produced by complex gravitational effects on the orbits of stars when another galaxy comes too close. All of these signs point to a violent past during which NGC 1316 annexed other galaxies and suggest that the disruptive behavior is continuing.”
You might better known NGC 1316 as Fornax A, the brightest radio source in the constellation Fornax and the fourth-brightest source in the sky. This is due to its supermassive black hole sucking up material in the area — and could actually be stronger because of the close encounters with other galaxies.
This image is a composite of archival pictures from the telescope. If you look closely, you can spot some fainter galaxies in the background, too.
Tsunami propagation forecast following the April 1, 2014 earthquake off the coast of Chile. Credit: NOAA's Pacific Tsunami Warning Center.
An 8.2-magnitude earthquake off the coast of northern Chile on April 1, 2014 was followed by at least a dozen significant aftershocks, including one with a magnitude of 6.2. This activity initially generated tsunami warnings across the Pacific, but the warnings were later canceled except for the coastal regions of Chile and Peru, according to NOAA’s Pacific Tsunami Warning Center.
Tsunami waves of more than 2 meters (6 feet) came ashore on the coast of Pisagua, Chile and 2.13 meter (7-foot) waves were reported in Iquique, Chile, according to the PTWC. The U.S Geological Survey reported the quake major quake was centered offshore about 96 km (60 miles) northwest of Iquique, at a depth of 20 km (12.5 miles).
At the time of this writing, the quake has reportedly caused only minor damage in Chile with two possible casualties, but several people are missing. There was a small landslide, several large fires, along with damaged boats and some flooding in Iquique due to the tsunami, according to Earthquakereport.com.
Chile’s National Emergency Office tweeted Tuesday night that it was asking everyone to evacuate the country’s coastal areas, and reports in the news and on social media said that the evacuations were orderly.
This earthquake follows several weeks of seismic activity in the South American Pacific region. On March 16, a 6.7-magnitude earthquake struck 60 km (37 miles)northwest of Iquique, according to the USGS. A 6.1-magnitude hit the same area one week later.
Chile is one of the most seismically active countries in the world, and is along the so-called “Ring of Fire,” an arc of volcanoes and fault lines circling the Pacific Basic that is prone to frequent earthquakes and volcanic eruptions.
The strongest earthquake ever recorded on Earth also took place happened in Chile. A magnitude-9.5 quake in 1960 killed more than 5,000 people. The most recent large quake in February 2010 hit central and southern Chile with a magnitude of 8.8, followed by a tsunami that left more than 500 dead with $30 billion in damage to property.
Tsunami waves travel about 800 km per hour, (500 miles per hour). That seems fast, but compared to a seismic wave it is slow. The speed of seismic wave, the P wave (or primary wave, which is the fastest kind of seismic wave) is about 8 km per second, or 30,000 km per hour.
You can compare a tsuanmi wave to the speed of a jet plane.
But while scientists can predict the speed and the direction of tsunamis fairly well, the height at a given location is can be very hard to predict, according to Anne Sheehan from the University of Colorado at Boulder, who spoke to Universe Today for a previous article about the science behind a tsunami.
“For predicting an ensuing tsunami, to have data on the earthquake itself — getting its epicenter located and knowing its size as accurately as possible plays a big role,” she said, “and the USGS plays a big role in getting that information out as quickly as possible.
Update: Here’s an animation from NOAA of the prediction of the tsunami following the April 1 quake in Chile:
A tiny crescent Moon, with only about 1% of the lunar surface illuminated, one day a few hours after the New Moon phase. March 31, 2014 from Sulmona, Abruzzo, Italy. Credit and copyright: Giuseppe Petricca.
Last night, you could have sung that old astronomical favorite, “By the light of the slivery Moon.” Yep, it was a teeny, tiny sliver of a crescent Moon, with just under 2% of the lunar surface illuminated. In fact, depending on where you live, the sliver could have been even tinier. Giuseppe Petricca from Sulmona, Abruzzo, Italy snapped a 1% illuminated Moon (above) and then realized he also managed to capture images of the crescent Moon during the day when the Moon was just 0.7% illuminated! (below) “It was less than a day since the New Moon!” Giuseppe said via email. “I was absolutely amazed, to say the least!”
See his daytime image below, plus many more “slivery” tiny crescent Moons as seen from around the world:
The tiny crescent Moon captured during the daytime in Sulmona, Abruzzo, Italy, in a 0.7% phase, minus than a day since New Moon. Credit and copyright: Giuseppe Petricca. The one-day old crescent Moon on March 31, 2014. Credit and copyright: Robert Sparks.
The 1.2 day old Moon, 2% illuminated, from Weatherly, PA. Inset picture taken with 12″ Meade telescope. Credit and copyright: Tom Wildoner. The Moon at sunset with only 2% of its surface illuminated. Credit and copyright: Héctor Barrios.A thin crescent Moon on April 1, 2014. Credit and copyright: Jason Hill.
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