Chasms, craters, and a dark north polar region are revealed in this image of Pluto’s largest moon Charon taken by New Horizons on July 11, 2015. The annotated version includes a diagram showing Charon’s north pole, equator, and central meridian, with the features highlighted. Credits: NASA/JHUAPL/SWRI
Beginning in 1978, astronomers began to discover that Pluto – the most distant known object from the Sun (at the time) – had its own moons. What had once been thought to be a solitary body occupying the outer edge of our Solar System suddenly appeared to have a system with a large moon Charon. And as time went on, a total of four moons would be discovered.
Of these, Charon is the largest and most easily observed, hence why it was discovered first. In addition to being the biggest of its peers, its also quite large in comparison to Pluto. As such, Charon has always had something of a unique relationship with its parent body, and stands apart as far as objects in the outer Solar System are concerned.
The Pluto system seen from the surface of Hydra. Credit: NASA
In 1930, Pluto was observed for the first time. For many decades, astronomers thought that the “ninth planet of the Solar System” was a solitary object. But by 1978, astronomers discovered that it also had a moon roughly half its size. This moon would come to be known as Charon, and it would be the first of many discoveries made within the Pluto’s system.
In fact, within the last decade, four additional satellites have been discovered in orbit of Pluto. Of these, the outermost to be observed is the moon now known as Hydra.
Discovery: Hydra was first discovered in June 2005 by the Hubble Space Telescope‘s “Pluto Companion Search Team”, using images that were taken on May 15th and 18th of that year. At the time, the team was preparing for the launch of the New Horizons mission to Pluto, seeking to gain as much information as they could about any addition Plutonian moons.
By June, Hydra was again discovered. This time, it was independently observed by two members of the team, along with Nix – another small Plutonian moon. The discoveries were announced on October 31st, 2005, and were provisionally given the designations of S/2005 P 1 and S/2005 P 2 (for Hydra and Nix, respectively).
Artist’s illustration comparing the scale and comparative brightness of Pluto’s small satellites. Credits: NASA/ESA/A. Feild (STScI)
Name: By June 21st, 2006, the name Hydra was assigned by the IAU (along with the formal designation Pluto III). The name Hydra, which is derived from the nine-headed serpent of Greek mythology, was selected for two reasons. The letter H refers to the Hubble Telescope, which was used to make the discovery, while the nine-headed serpent referred to Pluto’s tenure as the ninth planet of the Solar System.
Size, Mass and Orbit: Although its size has not been directly measured, calculations based on its brightness have indicated that Hydra’s diameter is between 40 and 160 kilometers (38 and 104 mi). Similar measurements estimate its mass to be in the vicinity of 4.2 x 1017 kg. Because of the uncertainty in these measurements, Hydra is either comparable in size to either the main moons of Saturn and Neptune, or the inner and irregular moons of Jupiter, Saturn and Uranus.
Hydra orbits Pluto at a distance of about 65,000 km with a very low eccentricity (0.0059) and an orbital inclination of about 0.24°. It orbits in the same plane as Charon and Nix and has an orbital period of 38.2 days.
Composition: Little is known about Hydra’s composition, and its density and albedo are both currently unknown. However, it is believed that if its diameter is towards the lower end of its estimated range (40 km), then it must have a geometric albedo similar to Charons (35%).
Labeled image of Hydra released upon IAU name approval. Credit: NASA/ESA/Hubble
However, assuming it is at the higher end of that range, it would likely have a reflectivity of about 4%, like the darkest Kuiper belt objects. Like all outer bodies in the outer Solar System, and its host planet Pluto, it is possible that Hydra’s composition is differentiated into a rocky core and an icy mantle that contains nitrogen and methane in ice form.
At the time of its discovery, Hydra appeared to be brighter than Nix. Observations made with the Hubble Telescope in 2005–06, which specifically targeting the two moons, once again confirmed that Hydra is the brighter of the two. Hydra appears to be spectrally neutral like Charon and Nix (i.e. greyish), whereas Pluto is reddish.
Interesting Facts: Hydra, not being massive enough to form a spheroid under its own gravity, is believed to be oblong in shape – the same holds true for Pluto’s moon of Nix. As with the rest of the Pluto system, Hydra was imaged by NASA’s New Horizons spacecraft in February of 2015. When New Horizons conducts its flyby at 7:49:57 a.m. EDT, July 14, 2015, it will provide the most detailed images of Hydra and the Pluto system to date.
How long would it take for the gravitational well created by the Sun to disappear, and the Earth and the rest of the planets fly off into space?
In the very first episode of the Guide to Space, a clean shaven version of me, hunched over in my basement explained how long it takes for light to get from the Sun to the Earth. To answer that question, it takes light about 8 minutes and 20 seconds to make the trip.
In other words, if the Sun suddenly disappeared from space itself, we’d still see it shining in the sky for over 8 minutes before the everything went dark. Martians would take about 12 minutes to notice the Sun was gone, and New Horizons which is nearly at Pluto wouldn’t see a change for over 4 hours.
Although this idea is a little mind-bending, I’m sure you’ve got your head wrapped around it. We’ve sure gone on about it here on this show. The further you look into space, the further you’re looking back in time because of the speed of light, but have you ever considered the speed of gravity?
Let’s go back to that original example and remove the Sun again. How long would it take for the gravitational well created by the Sun to disappear.
When would the Earth and the rest of the planets fly off into space without the Sun holding the whole Solar System together with its gravity? Would it happen instantly, or would it take time for the information to reach Earth?
It sounds like a simple question, but it’s actually really tough to tell. The force of gravity, compared to other forces in the Universe, is actually pretty weak. It’s practically impossible to test in the laboratory.
According to Einstein’s Theory of Relativity, distortions in spacetime caused by mass – also known as gravity – will propagate out at the speed of light. In other words, the light from the Sun and the gravity of the Sun should disappear at exactly the same time from the Earth’s perspective.
But that’s just a theory and a bunch of fancy math. Is there any way to test this out in reality? Astronomers have figured a way to deduce this indirectly by watching the interactions with massive objects in space.
In the binary system PSR 1913+16, there’s a pair of pulsars orbiting each other within just a few times bigger than the width of the Sun. As they spin around each other, the pulsars warp the spacetime themselves by releasing gravitational waves. And this release of gravitational waves causes the pulsars to slow down.
It’s amazing that astronomers can even measure this orbital decay, but the even more amazing part is that they use this process to measure the speed of gravity. When they did the calculations, astronomers determined the speed of gravity to be within 1% of the speed of light – that’s close enough.
Scientists have also used careful observations of Jupiter to get at this number. By watching how Jupiter’s gravity warps the light from a background quasar as it passes in front, they were able to determine that the speed of gravity is between 80% and 120% of the speed of light. Again, that’s close enough.
So there you go. The speed of gravity equals the speed of light. And should the Sun suddenly disappear, we’ll be glad to get all the bad news at the same time.
Gravity is a harsh mistress. Tell us a story about a time gravity was too fast for you. Put it in the comments below.
An artist's illustration of Pluto. Credit: NASA/New Horizons
First discovered in 1930, Pluto was considered to be the ninth planet in our Solar System for many decades. And though its status has since been downgraded to that of a dwarf planet, thanks to the discovery of Eris in 2004, Pluto continues to fascinate and intrigue astronomers.
And with the New Horizons mission fast approaching the planet, astronomers are eagerly anticipating the return of photographs and data that will help them answer some burning questions they have about this celestial body – not the least of which is whether or not it supports life!
Surface Conditions:
To be fair, there is virtually no chance that Pluto has life living on its surface. For starters, it orbits our Sun at extreme distances, ranging from 29.657 AU (4,437,000,000 km) at perihelion to 48.871 AU (7,311,000,000 km) at aphelion. At this distance, surface temperatures can reach as low as 33 K (-240 °C or -400 °F).
Not only does water freeze solid at these temperatures, but other liquids and gases that are present on Pluto’s surface – such as methane (CH4), nitrogen gas (N²), and carbon monoxide (CO) – also freeze solid. These compounds have much lower freezing points than water, and so the chance of life surviving under these conditions is slim to nil.
An artist’s concept of frosty Pluto. Credit: ESO/ L. Calçada
And while Pluto has a thin atmosphere, it consists mainly of nitrogen gas, methane and carbon monoxide, which exist in equilibrium with their ices on the surface. At the same time, the surface pressure ranges from s from 6.5 to 24 ?bar (0.65 to 2.4 Pa), which is roughly one million to 100,000 times less than Earth’s atmospheric pressure.
This atmosphere also undergoes transitions as Pluto gets closer and farther away from the Sun. Basically, when Pluto is at perihelion, the atmosphere freezes solid; when it is at aphelion, the surface temperature increases, causing the ices to sublimate.
As such, there is simply no way life could survive on the surface of Pluto. Between the extreme cold, low atmospheric pressure, and constant changes in the atmosphere, no known organism could survive. However, that does not rule out the possibility of life being found inside the planet.
Interior: Like many moons and smaller planetoids in the Outer Solar System, scientists believe that Pluto’s internal structure is differentiated, with rocky material having settled into a dense core surrounded by a mantle of ice. The diameter of the core is believed to be approximately 1700 km (accounting for 70% of Pluto’s diameter), whereas the ice layer is estimated to be 100 to 180 km thick at the core-mantle boundary.
The Theoretical structure of Pluto, consisting of 1. Frozen nitrogen 2. Water ice 3. Rock. Credit: NASA/Pat Rawlings
Because the decay of radioactive elements would eventually heat the ices enough for the rock to separate from them, it is possible Pluto has a liquid water ocean beneath its mantle. In 2011, planetary scientists Guillaume Robuchon and Francis Nimmo of the University of California at Santa Cruz modeled the thermal evolution of Pluto and studied the behavior of the shell to see how the surface would be affected by the presence of an ocean below.
What they determined was that the surface of Pluto would be covered by surface fractures that span the globe, owning to changes in the temperature, tensional stresses and compressional stresses of the liquid ocean below. Though no visual data exists to support the existence of such surface features, the New Horizons mission is scheduled to be providing photographic evidence of the surface shortly.
Future Possibilities:
Another possibility is that in time, conditions will change that might allow for life to exist on Pluto. While Pluto sits well beyond our Sun’s habitable zone, both the size of our Sun, and the reach of that zone, will be subject to change. In the distant future – roughly 5.4 billion years from now – our Sun will expand into a red giant, increasing the amount of energy it gives off for a period of several million of years.
Once the core hydrogen is exhausted in 5.4 billion years, the Sun will expand into a subgiant phase and slowly double in size over about half a billion years. As it expands in size, it will consume the inner planets (including the Earth), and the habitable zone will move to the outer Solar System. Even before it becomes a red giant, the luminosity of the Sun will have nearly doubled, and Earth will be hotter than Venus is today.
This is an artist’s concept of a craggy piece of solar system debris that belongs to a class of bodies called trans-Neptunian objects (TNOs). Credit: NASA
It will then expand more rapidly over about half a billion years until it is over two hundred times larger than it is today, and a couple of thousand times more luminous. This then starts the red-giant-branch (RGB) phase which will last around a billion years, during which time the the Sun will lose around a third of its mass.
During that time, many objects in the Kuiper Belt will warm up significantly, which will include Pluto, Eris, and countless other Trans-Neptunian Objects (TNOs).
However, given the composition of these bodies, and the relatively short window in which they will be warmer and wetter, it is not likely that life will evolve from scratch. Instead, we would probably have to transport it there from Earth, assuming humanity is still living, and seed Pluto and other surviving bodies with vegetation and terrestrial organisms.
In short, the best answer to the question – is there life on Pluto? – is a resounding maybe. Another possible answer is maybe not, with the caveat that there may indeed be life there someday (i.e. us, if we’re still around). In the meantime, all we can do is wait for data to begin coming in from New Horizons, and scan it for the telltale signs that life is indeed there right now!
Haleakala, a giant shield volcano, forms the eastern bulwark of the island of Maui. Any volcanoes on an asteroid would not form large cones like this. Credit: National Geographic/Cathy Roberts
Hawaii is famous for its lovely mountains, tropical climate, and majestic oceanfront vistas. Another thing it is famous for is the string of volcanoes that dot its islands. As a land that sits atop a geographic hot spot – i.e. an area deep within the Earth’s mantle from which heat rises, forming magma that is then pushed to the surface – the island is also home to some serious volcanic activity.
Consider Haleakala, the massive shield volcano that constitutes more than 75% of the Hawaiian Island of Maui. The result of volcanic activity that took place roughly 1 million years ago, this volcano has played an active role in the geological and cultural history of the Hawaiian islands. Description and Naming: Like all shield volcanoes, Haleakala was formed from a series of highly fluid magma flows. This is the reason for its general appearance, as well as the designation – i.e. it resembles a broad shield lying on the ground. It’s tallest peak, which is named is Pu’u ‘Ula’ula (“Red Hill”) in native Hawaiian, measures 3,055 m (10,023 ft) tall.
At Haleakala’s summit lies a massive depression (crater) that measures some 11.25 km (7 miles) in diameter and nearly 800 m (2,600 ft) deep. The name Haleakala means literally “House of the Sun”, which was given to the general mountain area by the early Hawaiian people.
Sliding sands trail in the Haleakala Crater, Maui. Credit: Haleakala National Park
Geology: Haleakala is part of a sequence of lava flows that emerged near the end of East Maui. This region is believed to have begun experiencing lava flows about 2.0 million years ago, and it is estimated that the volcano formed from the ocean floor to its current shield-like shape over the course of the ensuing 600,000 years. The oldest exposed lava flow on East Maui is dated to 1.1 million years ago.
In the past 30,000 years, the volcanism on East Maui has been focused along the southwest and east rift zones. These two volcanic axes together form one gently curving arc that passes from La Perouse Bay (southwest flank of East Maui) through Haleakala Crater to Hana on the east flank.
The alignment of these axes continues east beneath the ocean as Haleakala Ridge, one of the longest rift zones along the Hawaiian Islands volcanic chain. The on-land segment of this lengthy volcanic line of vents is the zone of greatest hazard for future lava flows and cindery ash.
Contrary to popular belief, the Haleakala “crater” is not volcanic in origin, nor can it accurately be called a caldera (which is formed when the summit of a volcano collapses to form a depression). Scientists believe instead that the depression was formed when the headwalls of two large erosional valleys merged at the summit of the volcano.
Modern techniques have allowed geologists to accurately date the lava flows on Maui. Credit: D. Sherrod/USGS
History: Haleakala has produced numerous eruptions in the last 30,000 years, including in the last 500 years. The volcano has figured prominently in the island’s history of human occupation. In Hawaiian folklore, the crater at the summit was home to the grandmother of the demigod Maui. According to the legend, Maui’s grandmother helped him capture the sun and force it to slow its journey across the sky in order to lengthen the day.
Until recently, the East Maui Volcano was thought to have last erupted around 1790, based largely on comparisons of maps made during the voyages of the explorers La Perouse and George Vancouver. Recent advanced dating tests, however, have shown that the last eruption was more likely to have taken place in the 17th century.
Modern geologic mapping efforts began in 1997, which yielded the most detailed and accurate picture of Haleakala’s volcanic history to date. In addition, there are fears that the volcano is not extinct, but just currently dormant, and may erupt again within the next 500 years.
For these reasons, the U.S. Geological Survey maintains a sparse seismic network on Haleakala volcano and conducts periodic surveys, using GPS receivers that gather data about the volcano’s surface deformation or lack thereof.
The view from Haleakala at night, Haleakala National Park. Credit: travelbloggerbuzz.com
Modern Uses: In 1916, Haleakala National Park was created, a 30,183-acre (122.15 km2) park surrounding the summit depression, Kipahulu Valley on the southeast, and ‘Ohe‘o Gulch (and pools), extending to the shoreline in the Kipahulu area. Within the park, 19,270 acres (77.98 km2) is a wilderness area, which is why the park area was designated an International Biosphere Reserve in 1980.
The main feature of this part of the park is the famous Haleakala Crater. Two main trails lead into the crater from the summit area – the Halemau’u and Sliding Sands trails. Haleakala is popular with tourists and locals alike, who often venture to its summit – or to the visitor center just below the summit – to view the sunrise. There is lodging in the crater in the form of a few simple cabins.
Because of the clarity and stillness of the air, the summit of Haleakala is one of the most valuable spots for observatories. It is also far enough away from the city lights to avoid light pollution, and above one-third of the planet’s atmosphere. Hence why the summit is the location of an astrophysical research facility – known as “Science City” – which is operated by a number of U.S. government and academic organizations.
These include the U.S. Department of Defense, the University of Hawaii, the Smithsonian Institution, the US Air Force, the Federal Aviation Administration (FAA), and others. Some of the telescopes operated by the US Department of Defense are involved in researching man-made (e.g. spacecraft, monitoring satellites, rockets, and laser technology) rather than celestial objects.
The Science City research faciltiy, located at the summit of the Haleakala volcano. Credit: Wikipedia Commons/Tawker
The scientific program is run in collaboration with defense contractors in the Maui Research and Technology Park in Kihei. Despite concerns that Maui’s growing population will mean increased incidents of light pollution, new telescopes are being added – such as the Pan-STARRS in 2006.
Although another 500 years or more may pass before Haleakala erupts again, it’s also possible that new eruptions will begin in the near future. However, according to the United States Geological Survey (USGS) Volcano Warning Scheme for the United States, the Volcanic-Alert Level as of June 2013 was “normal”. Given the likelihood of significant environmental and property damage, not to mention the potential loss of life, one can only hope this holds true for the foreseeable future.
Sarychev volcano, (located in Russia's Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Credit: NASA
What if someone were to tell you that there’s a region in the world where roughly 90% of the world’s earthquakes occur. What if they were to tell you that this region is also home to over 75% of the world’s active and dormant volcanoes, and all but 3 of the world’s 25 largest eruptions in the last 11,700 years took place here.
Chances are, you’d think twice about buying real-estate there. But strangely enough, hundreds of millions of people live in this area, and some of the most densely-packed cities in the world have been built atop its shaky faults. We are talking about the Pacific Ring of Fire, a geologically and volcanically active region that stretches from one side of the Pacific to the other.
Definition:
Also known as the circum-Pacific belt, the “Ring of Fire” is a 40,000 km (25,000 mile) horseshoe-shaped basin that is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements. This ring accounts for 452 volcanoes (active and dormant), stretching from the southern tip of South America, up along the coast of North America, across the Bering Strait, down through Japan, and into New Zealand – with several active and dormant volcanoes in Antarctica closing the ring.
Tectonic Activity:
The Ring of Fire is the direct result of plate tectonics and the movement and collisions of lithospheric plates. These plates, which constitute the outer layer of the planet, are constantly in motion atop the mantle. Sometimes they collide, pull apart, or slide alongside each other; resulting in convergent boundaries, divergent boundaries, and transform boundaries.
The Pacific Ring of Fire, a string of volcanic regions extending from the South Pacific to South America. Credit: Public Domain
In the case of the former, subduction zones are often the result, where the heavier plate slips under the lighter plate – forming a deep trench. This subduction changes the dense mantle into buoyant magma, which rises through the crust to the Earth’s surface. Over millions of years, this rising magma creates a series of active volcanoes known as a volcanic arc.
These ocean trenches and volcanic arcs run parallel to one another. For instance, the Aleutian Islands in the U.S. state of Alaska run parallel to the Aleutian Trench. Both geographic features continue to form as the Pacific Plate subducts beneath the North American Plate. Meanwhile, the Andes Mountains of South America run parallel to the Peru-Chile Trench, created as the Nazca Plate subducts beneath the South American Plate.
In the case of divergent boundaries, these are formed when tectonic plates pull apart, forming rift valleys on the seafloor. When this happens, magma wells up in the rift as the old crust pulls itself in opposite directions, where it is cooled by seawater to form new crust. This upward movement and eventual cooling of this magma has created high ridges on the ocean floor over millions of years.
The East Pacific Rise is a site of major seafloor spreading in the Ring of Fire, located on the divergent boundary of the Pacific Plate and the Cocos Plate (west of Central America), the Nazca Plate (west of South America), and the Antarctic Plate. The largest known group of volcanoes on Earth is found underwater along the portion of the East Pacific Rise between the coasts of northern Chile and southern Peru.
The different type of tectonic plate boundaries. Credit: oceanexplorer.noaa.gov
A transform boundary is formed when tectonic plates slide horizontally and parts get stuck at points of contact. Stress builds in these areas as the rest of the plates continue to move, which causes the rock to break or slip, suddenly lurching the plates forward and causing earthquakes. These areas of breakage or slippage are called faults, and the majority of Earth’s faults can be found along transform boundaries in the Ring of Fire.
The San Andreas Fault, stretching along the central west coast of North America, is one of the most active faults on the Ring of Fire. It lies on the transform boundary between the North American Plate, which is moving south, and the Pacific Plate, which is moving north. Measuring about 1,287 kilometers (800 miles) long and 16 kilometers (10 miles) deep, the fault cuts through the western part of the U.S. state of California.
Plate Boundaries:
The eastern section of the Ring of Fire is the result of the Nazca Plate and the Cocos Plate being subducted beneath the westward moving South American Plate. Meanwhile, the Cocos Plate is being subducted beneath the Caribbean Plate, in Central America. A portion of the Pacific Plate along with the small Juan de Fuca Plate are being subducted beneath the North American Plate.
Along the northern portion, the northwestward-moving Pacific plate is being subducted beneath the Aleutian Islands arc. Farther west, the Pacific plate is being subducted along the Kamchatka Peninsula arcs on south past Japan.
The Earth’s Tectonic Plates. Credit: msnucleus.org
The southern portion is more complex, with a number of smaller tectonic plates in collision with the Pacific plate from the Mariana Islands, the Philippines, Bougainville, Tonga, and New Zealand. This portion excludes Australia, since it lies in the center of its tectonic plate.
Indonesia lies between the Ring of Fire along the northeastern islands adjacent to and including New Guinea and the Alpide belt along the south and west from Sumatra, Java, Bali, Flores, and Timor. The famous and very active San Andreas Fault zone of California is a transform fault which offsets a portion of the East Pacific Rise under southwestern United States and Mexico.
Volcanic Activity:
Most of the active volcanoes on The Ring of Fire are found on its western edge, from the Kamchatka Peninsula in Russia, through the islands of Japan and Southeast Asia, to New Zealand. Mount Ruapehu in New Zealand is one of the more active volcanoes in the Ring of Fire, with yearly minor eruptions, and major eruptions occurring about every 50 years.
Krakatau, perhaps better known as Krakatoa, is an island volcano in Indonesia. Krakatoa erupts less often than Mount Ruapehu, but much more spectacularly. Beneath Krakatoa, the denser Australian Plate is being subducted beneath the Eurasian Plate. An infamous eruption in 1883 destroyed the entire island, sending volcanic gas, volcanic ash, and rocks as high as 80 kilometers (50 miles) in the air. A new island volcano, Anak Krakatau, has been forming with minor eruptions ever since.
Mount Fuji, Japan, as seen from the ISS. Credit: NASA
Mount Fuji, Japan’s tallest and most famous mountain, is an active volcano in the Ring of Fire. Mount Fuji last erupted in 1707, but recent earthquake activity in eastern Japan may have put the volcano in a “critical state.” Mount Fuji sits at a “triple junction,” where three tectonic plates (the Amur Plate, Okhotsk Plate, and Philippine Plate) interact.
The Ring of Fire’s eastern half also has a number of active volcanic areas, including the Aleutian Islands, the Cascade Mountains in the western U.S., the Trans-Mexican Volcanic Belt, and the Andes Mountains. Mount St. Helens, in the U.S. state of Washington, is an active volcano in the Cascade Mountains.
Below Mount St. Helens, both the Juan de Fuca and Pacific plates are being subducted beneath the North American Plate. Its historic 1980 eruption lasted 9 hours and covered 11 U.S. states with tons of volcanic ash. The eruption caused the deaths of 57 people, over a billion dollars in property damage, and reduced hundreds of square miles to wasteland.
Popocatépetl is one of the most active and dangerous volcanoes in the Ring of Fire, with 15 recorded eruptions since 1519. The volcano lies on the Trans-Mexican Volcanic Belt, which is the result of the small Cocos Plate subducting beneath the North American Plate. Located close to the urban areas of Mexico City and Puebla, Popocatépetl poses a risk to the more than 20 million people that live close enough to be threatened by a destructive eruption.
Map of the Earth showing the relation between fault lines (blue) and zones of volcanic activity (red). Credit: zmescience.com
Earthquakes:
Scientists have known for some time that the majority of the seismic activity occurs along plate boundaries. Hence why roughly 90% of the world’s earthquakes – which is estimated to be around 500,000 a year, one-fifth of which are detectable – occur around the Pacific Rim, where multiple plate boundaries exist.
As a result, earthquakes are a regular occurrence in places like Japan, Indonesia and New Zealand in Asia and the South Pacific; Alaska, British Columbia, California and Mexico in North America; and El Salvador, Guatemala, Peru and Chile in Central and South America. Where fault lines run beneath the ocean, larger earthquakes in these regions also trigger tsunamis.
The most well-known tsumanis to take place in the Ring of Fire include the 2004 Indian Ocean earthquake and tsunami. This was the most devastating tsunami of its kind in modern times, killing around 230,000 people and laying waste to communities throughout Indonesia, Thailand, and Southern Asia.
In 2010, an earthquake triggered a tsunami which caused 4334 confirmed deaths and devastating several coastal towns in south-central Chile, including the port at Talcahuano. The earthquake also generated a blackout that affected 93 percent of the Chilean population.
In 2011, an earthquake off the Pacific coast of Tohoku led to a tsunami that struck Japan and led to 5,891 deaths, 6,152 injuries, and 2,584 people to be declared missing across twenty prefectures. The tsunami also caused meltdowns at three reactors in the Fukushima Daiichi Nuclear Power Plant complex.
The Ring of Fire is a crucial region for many reasons. It serves as one of the main boundary regions for the tectonic plates of over half of the globe. It also affects the lives of millions if not billions of people who live in these regions. For many of the people who live in the Pacific Ring of Fire, the reality of a volcanic eruption or earthquake is commonplace and a challenge they have come to deal with over time.
At the same time, the volcanic activity has also provided many valuable resources, such as rich farmland and the possibility of tapping geothermal activity for heating and electricity. As always, nature gives with one hand and takes with the other!
If you have enjoyed this article there are several others on Universe Today that you will find interesting. Here is one called 10 Interesting Facts About Volcanoes. There is also a great article about plate tectonics.
You can also find some good resources online. There is a companion site for the PBS program Savage Earth that talks about the Ring of Fire. You can also check out the USGS site to see a detailed map of the Pacific Ring of Fire and more detailed information about plate tectonics.
You can also listen to Astronomy Cast. Episode 141 talks about volcanoes.
Why Don't We Send Probes "Up" In The Solar System?
Wouldn’t it be easier to see what’s outside the solar system if we just send out probes straight up?
Dammit, science people! Why are you always firing probes “outwards”? Then they have to go past all this stuff, like planets and asteroids and crap to escape the solar system. Don’t you realize that if we want to see what’s outside the solar system we just need to shoot them straight up?
Then we don’t have to go past all that junk, and we can finally see what’s between us and the next star system over! Is it thick goo? Is it thin goo? Is it the aether?!
What the heck is wrong with you! It’s so easy. Just go up! Why are we always going out?
Whenever we talk Solar System, we’re always using flat objects for reference. Plates, flying disks, pancakes and pizzas, as it’s arranged in a flat disk known as the plane of the ecliptic.
Formed from a blob of hydrogen gas and dust in the solar nebula. Gravity pulled everything together, and the conservation of angular momentum set the whole thing spinning, faster and faster. The spinning pulled the whole Solar System into the disk we see today, with our star at the center and the planets embedded in the surrounding disk. As a result, the Sun, Moon, planets and their moons all move through a relatively small region in the sky.
This definitely makes things easier to send spacecraft from world to world. NASA’s Voyager 2 was able to visit Jupiter, Saturn, Uranus and Neptune because they were all lined up like dominoes.
When Willie Sutton was asked why he robbed banks, he answered, “that’s where the money is,” and we explore along the plane of the ecliptic because that’s where the science is. Everything in our Solar System is arranged along this flat area, so it makes sense to look along this region.
But wait! As you know, the Solar System isn’t actually flat. Some objects rise a little above or below the plane of the ecliptic. This is known as a planet’s orbital inclination.
Orbit of Mercury
Of all the planets, Mercury has the greatest with 7-percent. It’s even crazier for the the dwarf planets, Pluto is 17-percent off the plane of the ecliptic, and Eris is 44-percent.
One of the reasons Eris went undiscovered for so long is because it orbits so far outside the planet of the ecliptic. It wasn’t until Mike Brown and his team from Caltech looked far enough outside the usual hiding spaces that they found these additional dwarf planets.
There really isn’t much outside the flat plane of the ecliptic, it’s also much more difficult to get spacecraft to travel above or below. When spacecraft launch, they already have tremendous velocity just from the rotation of the Earth and the speed of the Earth orbiting the Sun.
I realize this is just more “outwardist” propaganda for you. So why no “up”? If you did want to go that way, you need a powerful rocket capable of creating velocity in this direction, or that direction.
If you wanted to escape the Earth’s gravity and explore the Solar System in the regular old way, you’d need to add about 10 km/s in velocity to your spacecraft. But for straight up, you’d need about 30 km/s, meaning more fuel, and compromises to your payload.
It still sounds like I’m making excuses. Here’s the deal, you might be amazed to learn that spacecraft actually have been sent “up”.
Artist impression of the Ulysses spacecraft. Credit: NASA/ESA
The European Space Agency’s Ulysses spacecraft, launched in 1990 had the goal of looking down on the Sun from above. It wasn’t possible to do this just with a rocket, but engineers were able to use a gravitational assist from Jupiter to kick Ulysses into an orbital inclination of 80-degrees, and for the first time, we were able to see the Sun from above and below.
A new European mission is in the works called the Solar Orbiter, and it’ll get into an orbital inclination of 90-degrees to be able to see the Sun’s poles directly for the first time. If all goes well, it’ll launch in 2018.
So, why don’t we go up? Actually, we do. We’re going “up” again very soon. It’s good to go up. It’s always good to get outside of our regular stomping grounds and see our Solar System from new angles and perspectives.
If you could send a probe anywhere in our Solar System, where would you choose?
NGC 1300, a spiral, barred galaxy viewed nearly face-on by the Hubble Space Telescope. Credit: NASA/ESA/Hubble
For millennia, human beings have stared up at the night sky and stood in awe of the Milky Way. Today, stargazers and amateur astronomers continue in this tradition, knowing that what they are witnessing is in fact a collection of hundreds of millions of stars and dust clouds, not to mention billions of other worlds.
But one has to wonder, if we can see the glowing band of the Milky Way, why can’t we see what lies towards the center of our galaxy? Assuming we are looking in the right direction, shouldn’t we able to see that big, bright bulge of stars with the naked eye? You know the one I mean, it’s in all the pictures!
Unfortunately, in answering this question, a number of reality checks have to be made. When it is dark enough, and conditions are clear, the dusty ring of the Milky Way can certainly be discerned in the night sky. However, we can still only see about 6,000 light years into the disk with the naked eye, and relying on the visible spectrum. Here’s a rundown on why that is.
Size and Structure:
First of all, the sheer size of our galaxy is enough to boggle the mind. NASA estimates that the Milky Way is between 100,000 – 120,000 light-years in diameter – though some information suggests it may be as much as 150,000 – 180,000 light-years across. Since one light year is about 9.5 x 1012km, this makes the diameter of the Milky Way galaxy approximately 9.5 x 1017 – 1.14 x 1018 km in diameter.
To put that in layman’s terms, that 950 quadrillion (590 quadrillion miles) to 1.14 quintillion km (7oo septendecillion miles). The Milky Way is also estimated to contain 100–400 billion stars, (although that could be as high as one trillion), and may have as many as 100 billion planets.
At the center, measuring approx. 10,000 light-years in diameter, is the tightly-packed group of stars known as the “bulge”. At the very center of this bulge is an intense radio source, named Sagittarius A*, which is likely to be a supermassive black hole that contains 4.1 million times the mass of our Sun.
We, in our humble Solar System, are roughly 28,000 light years away from it. In short, this region is simply too far for us to see with the naked eye. However, there is more to it than just that…
Radio image of the night sky. Credit: Max Planck Institute for Radio Astronomy, generated by Glyn Haslam.
Low Surface Brightness:
In addition to being a spiral barred galaxy, the Milky Way is what is known as a Low Surface Brightness (LSB) galaxy – a classification that refers to galaxies where their surface brightness is, when viewed from Earth, at least one magnitude lower than the ambient night sky. Essentially, this means that the sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be seen.
This makes the Milky Way difficult to see from any location on Earth where light pollution is common – such as urban or suburban locations – or when stray light from the Moon is a factor. But even when conditions are optimal, there still only so much we can see with the naked eye, for reasons that have much to do with everything that lies between us and the galactic core.
Dust and Gas:
Though it may not look like it to the casual observer, the Milky Way is full of dust and gas. This matter is known as as the interstellar medium, a disc that makes up a whopping 10-15% of the luminous/visible matter in our galaxy and fills the long spaces in between the stars. The thickness of the dust deflects visible light (as is explained here), leaving only infrared light to pass through the dust.
This dazzling infrared image from NASA’s Spitzer Space Telescope showing hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. Credit: NASA/JPL-Caltech
This makes infrared telescopes like the Spitzer Space Telescope extremely valuable tools in mapping and studying the galaxy, since it can peer through the dust and haze to give us extraordinarily clear views of what is going on at the heart of the galaxy and in star-forming regions. However, when looking in the visual spectrum, light from Earth, and the interference effect of dust and gas limit how far we can see.
Limited Instrumentation:
Astronomers have been staring up at the stars for thousands of years. However, it was only in comparatively recent times that they even knew what they were looking at. For instance, in his book Meteorologica, Aristotle (384–322 BC) wrote that the Greek philosophers Anaxagoras (ca. 500–428 BCE) and Democritus (460–370 BCE) had proposed that the Milky Way might consist of distant stars.
However, Aristotle himself believed the Milky Way was be caused by “the ignition of the fiery exhalation of some stars which were large, numerous and close together” and that these ignitions takes place in the upper part of the atmosphere. Like many of Aristotle’s theories, this would remain canon for western scholars until the 16th and 17th centuries, at which time, modern astronomy would begin to take root.
Meanwhile, in the Islamic world, many medieval scholars took a different view. For example, Persian astronomer Abu Rayhan al-Biruni (973–1048) proposed that the Milky Way is “a collection of countless fragments of the nature of nebulous stars”. Ibn Qayyim Al-Jawziyya (1292–1350) of Damascus similarly proposed that the Milky Way is “a myriad of tiny stars packed together in the sphere of the fixed stars” and that these stars are larger than planets.
Persian astronomer Nasir al-Din al-Tusi (1201–1274) also claimed in his book Tadhkira that: “The Milky Way, i.e. the Galaxy, is made up of a very large number of small, tightly clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color.”
Despite these theoretical breakthroughs, it was not until 1610, when Galileo Galilei turned his telescope towards the heavens, that proof existed to back up these claims. With the help of telescopes, astronomers realized for the first time that there were many, many more stars in the sky than the ones we can see, and that all of the ones that we can see are a part of the Milky Way.
Over a century later, William Herschel created the first theoretical diagram of what the Milky Way (1785) looked like. In it, he described the shape of the Milky Way as a large, cloud-like collection of stars, and claimed the Solar System was close to the center. Though erroneous, this was the first attempt at hypothesizing what our cosmic backyard looked like.
It was not until the 20th century that astronomers were able to get an accurate picture of what our Galaxy actually looks like. This began with astronomer Harlow Shapely measuring the distributions and locations of globular star clusters. From this, he determined that the center of the Milky Way was 28,000 light years from Earth, and that the center was a bulge, rather than a flat area.
This annotated artist’s conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA
In 1923, astronomer Edwin Hubble used the largest telescope of his day at the Mt. Wilson Observatory near Pasadena, Calif., to observe galaxies beyond our own. By observing what spiral galaxies look like throughout the universe, astronomers and scientists were able to get an idea of what our own looks like.
Since that time, the ability to observe our galaxy through multiple wavelengths (i.e. radio waves, infrared, x-rays, gamma-rays) and not just the visible spectrum has helped us to get an even better picture. In addition, the development of space telescopes – such as Hubble, Spitzer, WISE, and Kepler – have been instrumental in allowing us to make observations that are not subject to interference from our atmosphere or meteorological conditions.
But despite our best efforts, we are still limited by a combination of perspective, size, and visibility barriers. So far, all pictures that depict our galaxy are either artist’s renditions or pictures of other spiral galaxies. Until quite recently in our history, it was very difficult for scientists to gauge what the Milky Way looks like, mainly because we’re embedded inside it.
To get an actual view of the Milky Way Galaxy, several things would need to happen. First, we would need a camera that worked in space that had a wide field of view (aka. Hubble, Spitzer, etc). Then we’d need to fly that camera to a spot that’s roughly 100,000 light years above the Milky Way and point it back at Earth. With our current propulsion technology, that would take 2.2 billion years to accomplish.
Milky Way in infrared. Image credit: COBE
Fortunately, as noted already, astronomers have a few additional wavelengths they can use to see into the galaxy, and these are making much more of the galaxy visible. In addition to seeing more stars and more star clusters, we’re able to see more of the center of our Galaxy as well, which includes the supermassive black hole that has been theorized as existing there.
For some time, astronomers have had name for the region of sky that is obscured by the Milky Way – the “Zone of Avoidance“. Back in the days when astronomers could only make visual observations, the Zone of Avoidance took up about 20% of the night sky. But by observing in other wavelengths, like infrared, x-ray, gamma rays, and especially radio waves, astronomers can see all but about 10% of the sky. What’s on the other side of that 10% is mostly a mystery.
In short, progress is being made. But until such time that we can send a ship beyond our Galaxy that can take snapshots and beam them back to us, all within the space of our own lifetimes, we’ll be dependent on what we can observe from the inside.
And be to sure to check out Universe Today’s interview with Dr. Andrea Ghez, Professor of Astronomy at UCLA, talking about what is at the center of our Galaxy.
A lightning storm striking down in a rural area. Credit: noaanews.noaa.gov
Thunder and lightning. When it comes to the forces of nature, few other things have inspired as much fear, reverence, or fascination – not to mention legends, mythos, and religious representations. As with all things in the natural world, what was originally seen as a act by the Gods (or other supernatural causes) has since come to be recognized as a natural phenomena.
But despite all that human beings have learned over the centuries, a degree of mystery remains when it comes to lightning. Experiments have been conducted since the time of Benjamin Franklin; however, we are still heavily reliant on theories as to how lighting behaves.
Description: By definition, lightning is a sudden electrostatic discharge during an electrical storm. This discharge allows charged regions in the atmosphere to temporarily equalize themselves, when they strike an object on the ground. Although lightning is always accompanied by the sound of thunder, distant lightning may be seen but be too far away for the thunder to be heard.
Types: Lightning can take one of three forms, which are defined by what is at the “end” of the branch channel (i.e. lightning bolt). For example, there is intra-cloud lighting (IC), which takes place between electrically charged regions of a cloud; cloud-to-cloud (CC) lighting, where it occurs between one functional thundercloud and another; and cloud-to-ground (CG) lightning, which primarily originates in the thundercloud and terminates on an Earth surface (but may also occur in the reverse direction).
Multiple paths of cloud-to-cloud lightning, Swifts Creek, Australia.. Credit: fir0002/flagstaffotos.com.au
Intra-cloud lightning most commonly occurs between the upper (or “anvil”) portion and lower reaches of a given thunderstorm. In such instances, the observer may see only a flash of light without hearing any thunder. The term “heat-lightning” is often applied here, due to the association between locally experienced warmth and the distant lightning flashes.
In the case of cloud-to-cloud lightning, the charge typically originates from beneath or within the anvil and scrambles through the upper cloud layers of a thunderstorm, normally generating a lightning bolt with multiple branches.
Cloud-to-ground (CG) is the best known type of lightning, though it is the third-most common – accounting for approximately 25% cases worldwide. In this case, the lightning takes the form of a discharge between a thundercloud and the ground, and is usually negative in polarity and initiated by a stepped branch moving down from the cloud.
CG lightning is the best known because, unlike other forms of lightning, it terminates on a physical object (most often the Earth), and therefore lends itself to being measured by instruments. In addition, it poses the greatest threat to life and property, so understanding its behavior is seen as a necessity.
Frequency of lightning strikes throughout the world, based on data from NASA. Credit: Wikipedia/Citynoise
Properties: Lighting originates when wind updrafts and downdrafts take place in the atmosphere, creating a charging mechanism that separates electric charges in clouds – leaving negative charges at the bottom and positive charges at the top. As the charge at the bottom of the cloud keeps growing, the potential difference between cloud and ground, which is positively charged, grows as well.
When a breakdown at the bottom of the cloud creates a pocket of positive charge, an electrostatic discharge channel forms and begins traveling downwards in steps tens of meters in length. In the case of IC or CC lightning, this channel is then drawn to other pockets of positive charges regions. In the case of CG strikes, the stepped leader is attracted to the positively charged ground.
Many factors affect the frequency, distribution, strength and physical properties of a “typical” lightning flash in a particular region of the world. These include ground elevation, latitude, prevailing wind currents, relative humidity, proximity to warm and cold bodies of water, etc. To a certain degree, the ratio between IC, CC and CG lightning may also vary by season in middle latitudes.
About 70% of lightning occurs over land in the tropics where atmospheric convection is the greatest. This occurs from both the mixture of warmer and colder air masses, as well as differences in moisture concentrations, and it generally happens at the boundaries between them. In the tropics, where the freezing level is generally higher in the atmosphere, only 10% of lightning flashes are CG. At the latitude of Norway (around 60° North latitude), where the freezing elevation is lower, 50% of lightning is CG.
A series of lightning strikes imaged by the Nightpod camera aboard the ISS above Rome in 2012. Credit: ESA/NASA/André Kuipers
Effects: In general, lightning has three measurable effects on the surrounding environment. First, there is the direct effect of a lightning strike itself, in which structural damage or even physical harm can result. When lighting strikes a tree, it vaporizes sap, which can result in the trunk exploding or a large branches snapping off and falling to the ground.
When lightning strikes sand, soil surrounding the plasma channel may melt, forming tubular structures called fulgurites. Buildings or tall structures hit by lightning may be damaged as the lightning seeks unintended paths to ground. And though roughly 90% of people struck by lightning survive, humans or animals struck by lightning may suffer severe injury due to internal organ and nervous system damage.
Thunder is also a direct result of electrostatic discharge. Because the plasma channel superheats the air in its immediate vicinity, the gaseous molecules undergo a rapid increase in pressure and thus expand outward from the lightning creating an audible shock wave (aka. thunder). Since the sound waves propagate not from a single source, but along the length of the lightning’s path, the origin’s varying distances can generate a rolling or rumbling effect.
High-energy radiation also results from a lightning strike. These include x-rays and gamma rays, which have been confirmed through observations using electric field and X-ray detectors, and space-based telescopes.
A fulgerite formed in sandy patch as a result of a lightning strike. Credit: blogs.discovermagazine.com
Studies: The first systematic and scientific study of lightning was performed by Benjamin Franklin during the second half of the 18th century. Prior to this, scientists had discerned how electricity could be separated into positive and negative charges and stored. They had also noted a connection between sparks produced in a laboratory and lightning.
Franklin theorized that clouds are electrically charged, from which it followed that lightning itself was electrical. Initially, he proposed testing this theory by placing iron rod next to a grounded wire, which would be held in place nearby by an insulated wax candle. If the clouds were electrically charged as he expected, then sparks would jump between the iron rod and the grounded wire.
In 1750, he published a proposal whereby a kite would be flown in a storm to attract lightning. In 1752, Thomas Francois D’Alibard successfully conducted the experiment in France, but used a 12 meter (40 foot) iron rod instead of a kite to generate sparks. By the summer of 1752, Franklin is believed to have conducted the experiment himself during a large storm that descended on Philadelphia.
For his upgraded version of the experiment, Franking attacked a key to the kite, which was connected via a damp string to an insulating silk ribbon wrapped around the knuckles of Franklin’s hand. Franklin’s body, meanwhile, provided the conducting path for the electrical currents to the ground. In addition to showing that thunderstorms contain electricity, Franklin was able to infer that the lower part of the thunderstorm was generally negatively charged as well.
An artistic rendition of Franklin’s kite experiment painted by Benjamin West. Credit: Public Domain
Little significant progress was made in understanding the properties of lightning until the late 19th century when photography and spectroscopic tools became available for lightning research. Time-resolved photography was used by many scientists during this period to identify individual lightning strokes that make up a lightning discharge to the ground.
Lightning research in modern times dates from the work of C.T.R. Wilson (1869 – 1959) who was the first to use electric field measurements to estimate the structure of thunderstorm charges involved in lightning discharges. Wilson also won the Nobel Prize for the invention of the Cloud Chamber, a particle detector used to discern the presence of ionized radiation.
By the 1960’s, interest grew thanks to the intense competition brought on by the Space Age. With spacecraft and satellites being sent into orbit, there were fears that lightning could post a threat to aerospace vehicles and the solid state electronics used in their computers and instrumentation. In addition, improved measurement and observational capabilities were made possible thanks to improvements in space-based technologies.
In addition to ground-based lightning detection, several instruments aboard satellites have been constructed to observe lightning distribution. These include the Optical Transient Detector (OTD), aboard the OrbView-1 satellite launched on April 3rd, 1995, and the subsequent Lightning Imaging Sensor (LIS) aboard TRMM, which was launched on November 28th, 1997.
The Colima Volcano (Volcán de Colima) pictured on March 29, 2015 with lightning. Credit and copyright: César Cantú.
Volcanic Lightning: Volcanic activity can produce lightning-friendly conditions in multiple ways. For instance, the powerful ejection of enormous amounts of material and gases into the atmosphere creates a dense plume of highly charged particles, which establishes the perfect conditions for lightning. In addition, the ash density and constant motion within the plume continually produces electrostatic ionization. This in turn results in frequent and powerful flashes as the plume tries to neutralize itself.
This type of thunderstorm is often referred to as a “dirty thunderstorm” due to the high solid material (ash) content. There have been several recorded instances of volcanic lightning taking place throughout history. For example, during the eruption of Vesuvius in 79 CE, Pliny the Younger noted several powerful and frequent flashes taking place around the volcanic plume.
Extraterrestrial Lightning: Lightning has been observed within the atmospheres of other planets in our Solar System, such as Venus, Jupiter and Saturn. In the case of Venus, the first indications that lightning may be present in the upper atmosphere were observed by the Soviet Venera and U.S. Pioneer missions in the 1970s and 1980s. Radio pulses recorded by the Venus Express spacecraft (in April 2006) were confirmed as originating from lightning on Venus.
Artist concept of a lightning stormVenus. Credit: NASA)
Thunderstoms that are similar to those on Earth have been observed on Jupiter. They are believed to be the result of moist convection with Jupiter’s troposphere, where convective plumes bring wet air up from the depths to the upper parts of the atmosphere, where it then condenses into clouds of about 1000 km in size.
The imaging of the night-side hemisphere of Jupiter by the Galileo in the 1990 and by the Cassini spacecraft in December of 2000 revealed that storms are always associated with lightning on Jupiter. While lighting strikes are on average a few times more powerful than those on Earth, they are apparently less frequent. A few flashes have been detected in polar regions, making Jupiter the second known planet after Earth to exhibit polar lightning.
Lighting has also been observed on Saturn. The first instance occurred in 2010 when the Cassini space probe detected flashes on the night-side of the planet, which happened to coincide with the detection of powerful electrostatic discharges. In 2012, images taken by the Cassini probe in 2011 showed how the massive storm that wrapped the northern hemisphere was also generating powerful flashes of lightning.
Once thought to be the “hammer of the Gods”, lightning has since come to be understood as a natural phenomena, and one that exists on other terrestrial worlds and even gas giants. As we come to learn more about how lighting behaves here on Earth, that knowledge could go a long way in helping us to understand weather systems on other worlds as well.
With astronomers discovering new planets and other celestial objects all the time, you may be wondering what the newest planet to be discovered is. Well, that depends on your frame of reference. If we are talking about our Solar System, then the answer used to be Pluto, which was discovered by the American astronomer Clyde William Tombaugh in 1930.
Unfortunately, Pluto lost its status as a planet in 2006 when it was reclassified as a dwarf planet. Since then, another contender has emerged for the title of “newest planet in the Solar System” – a celestial body that goes by the name of Eris – while beyond our Solar System, thousands of new planets are being discovered.
But then, the newest planet might be the most recently discovered extrasolar planet. And these are being discovered all the time.
