Guide to Space Archives

October 1, 2016October 2, 2016 by Matt Williams

What Happens When Galaxies Collide?

This illustration shows a stage in the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy, as it will unfold over the next several billion years. In this image, representing Earth's night sky in 3.75 billion years, Andromeda (left) fills the field of view and begins to distort the Milky Way with tidal pull. (Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger)

We don’t want to scare you, but our own Milky Way is on a collision course with Andromeda, the closest spiral galaxy to our own. At some point during the next few billion years, our galaxy and Andromeda – which also happen to be the two largest galaxies in the Local Group – are going to come together, and with catastrophic consequences.

Stars will be thrown out of the galaxy, others will be destroyed as they crash into the merging supermassive black holes. And the delicate spiral structure of both galaxies will be destroyed as they become a single, giant, elliptical galaxy. But as cataclysmic as this sounds, this sort of process is actually a natural part of galactic evolution.

Astronomers have know about this impending collision for some time. This is based on the direction and speed of our galaxy and Andromeda’s. But more importantly, when astronomers look out into the Universe, they see galaxy collisions happening on a regular basis.

The Antennae galaxies. Credit: Hubble / ESA — *The Antennae galaxies, a pair of interacting galaxies located 45 – 65 million light years from Earth. Credit: Hubble / ESA*

Gravitational Collisions:

Galaxies are held together by mutual gravity and orbit around a common center. Interactions between galaxies is quite common, especially between giant and satellite galaxies. This is often the result of a galaxies drifting too close to one another, to the point where the gravity of the satellite galaxy will attract one of the giant galaxy’s primary spiral arms.

In other cases, the path of the satellite galaxy may cause it to intersect with the giant galaxy. Collisions may lead to mergers, assuming that neither galaxy has enough momentum to keep going after the collision has taken place. If one of the colliding galaxies is much larger than the other, it will remain largely intact and retain its shape, while the smaller galaxy will be stripped apart and become part of the larger galaxy.

Such collisions are relatively common, and Andromeda is believed to have collided with at least one other galaxy in the past. Several dwarf galaxies (such as the Sagittarius Dwarf Spheroidal Galaxy) are currently colliding with the Milky Way and merging with it.

However, the word collision is a bit of a misnomer, since the extremely tenuous distribution of matter in galaxies means that actual collisions between stars or planets is extremely unlikely.

The Atacama Large Millimeter/submillimeter Array (ALMA) and many other telescopes on the ground and in space have been used to obtain the best view yet of a collision that took place between two galaxies when the Universe was only half its current age. The astronomers enlisted the help of a galaxy-sized magnifying glass to reveal otherwise invisible detail. These new studies of the galaxy H-ATLAS J142935.3-002836 have shown that this complex and distant object looks surprisingly like the well-known local galaxy collision, the Antennae Galaxies. In this picture you can see the foreground galaxy that is doing the lensing, which resembles how our home galaxy, the Milky Way, would appear if seen edge-on. But around this galaxy there is an almost complete ring — the smeared out image of a star-forming galaxy merger far beyond. This picture combines the views from the NASA/ESA Hubble Space Telescope and the Keck-II telescope on Hawaii (using adaptive optics). Credit: ESO/NASA/ESA/W. M. Keck Observatory — *Image obtained by the Hubble Space Telescope and the Keck-II telescope, showing a collision that took place billions of years ago. Credit: ESO/NASA/ESA/W. M. Keck Observatory*

Andromeda–Milky Way Collision:

In 1929, Edwin Hubble revealed observational evidence which showed that distant galaxies were moving away from the Milky Way. This led him to create Hubble’s Law, which states that a galaxy’s distance and velocity can be determined by measuring its redshift – i.e. a phenomena where an object’s light is shifted toward the red end of the spectrum when it is moving away.

However, spectrographic measurements performed on the light coming from Andromeda showed that its light was shifted towards the blue end of the spectrum (aka. blueshift). This indicated that unlike most galaxies that have been observed since the early 20th century, Andromeda is moving towards us.

In 2012, researchers determined that a collision between the Milky Way and the Andromeda Galaxy was sure to happen, based on Hubble data that tracked the motions of Andromeda from 2002 to 2010. Based on measurements of its blueshift, it is estimated that Andromeda is approaching our galaxy at a rate of about 110 km/second (68 mi/s).

At this rate, it will likely collide with the Milky Way in around 4 billion years. These studies also suggest that M33, the Triangulum Galaxy – the third largest and brightest galaxy of the Local Group – will participate in this event as well. In all likelihood, it will end up in orbit around the Milky Way and Andromeda, then collide with the merger remnant at a later date.

Galactic Wrecks Far from Earth: These images from NASA's Hubble Space Telescope's ACS in 2004 and 2005 show four examples of interacting galaxies far away from Earth. The galaxies, beginning at far left, are shown at various stages of the merger process. The top row displays merging galaxies found in different regions of a large survey known as the AEGIS. More detailed views are in the bottom row of images. (Credit: NASA; ESA; J. Lotz, STScI; M. Davis, University of California, Berkeley; and A. Koekemoer, STScI) — Images from Hubble’s ACS in 2004 and 2005 show four examples of interacting galaxies (at various stages in the process) far away from Earth. Credit: NASA/ESA/J. Lotz, STScI/M. Davis, University of California, Berkeley/A. Koekemoer, STScI.

Consequences:

In a galaxy collision, large galaxies absorb smaller galaxies entirely, tearing them apart and incorporating their stars. But when the galaxies are similar in size – like the Milky Way and Andromeda – the close encounter destroys the spiral structure entirely. The two groups of stars eventually become a giant elliptical galaxy with no discernible spiral structure.

Such interactions can also trigger a small amount of star formation. When the galaxies collide, it causes vast clouds of hydrogen to collect and become compressed, which can trigger a series of gravitational collapses. A galaxy collision also causes a galaxy to age prematurely, since much of its gas is converted into stars.

After this period of rampant star formation, galaxies run out of fuel. The youngest hottest stars detonate as supernovae, and all that’s left are the older, cooler red stars with much longer lives. This is why giant elliptical galaxies, the results of galaxy collisions, have so many old red stars and very little active star formation.

Despite the Andromeda Galaxy containing about 1 trillion stars and the Milky Way containing about 300 billion, the chance of even two stars colliding is negligible because of the huge distances between them. However, both galaxies contain central supermassive black holes, which will converge near the center of the newly-formed galaxy.

Two galaxies are squaring off in Corvus and here are the latest pictures.. Credit: B. Whitmore (STScI), F. Schweizer (DTM), NASA — *Two galaxies colliding in the Corvus constellation. Credit: B. Whitmore (STScI), F. Schweizer (DTM),*

This black hole merger will cause orbital energy to be transferred to stars, which will be moved to higher orbits over the course of millions of years. When the two black holes come within a light year of one another, they will emit gravitational waves that will radiate further orbital energy, until they merge completely.

Gas taken up by the combined black hole could create a luminous quasar or an active nucleus to form at the center of the galaxy. And last, the effects of a black hole merger could also kick stars out of the larger galaxy, resulting in hypervelocity rogue stars that could even carry their planets with them.

Today, it is understood that galactic collisions are a common feature in our Universe. Astronomy now frequently simulate them on computers, which realistically simulate the physics involved – including gravitational forces, gas dissipation phenomena, star formation, and feedback.

And be sure to check out this video of the impending galactic collision, courtesy of NASA:

We have written many articles about galaxies for Universe Today. Here’s What is Galactic Cannibalism?, Watch Out! Galactic Collisions Could Snuff Out Star Formation, New Hubble Release: Dramatic Galaxy Collision, A Virtual Galactic Smash-Up!, It’s Inevitable: Milky Way, Andromeda Galaxy Heading for Collision, A Cosmic Collision: Our Best View Yet of Two Distant Galaxies Merging, and Determining the Galaxy Collision Rate.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We have also recorded an episode of Astronomy Cast about galaxies – Episode 97: Galaxies.

Sources:

September 30, 2016October 1, 2016 by Matt Williams

How Many Dogs Have Been to Space?

Laika statue outside a research facility in Moscow (AP Photo/RIA-Novosti, Alexei Nikolsky)

Becoming an astronaut is a rare honor. The rigorous selection process, the hard training, and then… the privilege of going into space! It is something few human beings will ever be privileged enough to experience. But what about other species of animal that have gone into space? Are we not being just the slightest bit anthropocentric in singling out humans for praise?

What about all those brave simians and mice that were sent into space? What about the guinea pigs and rats? And what of “Man’s Best Friend”, the brave canines that helped pave the way for “manned” spaceflight? During the 1950s and 60s, the Soviets sent over 20 dogs into space, some of which never returned. Here’s what we know about these intrepid canines who helped make humanity a space-faring race!

Background:

During the 1950s and 60s, the Soviets and Americans found themselves locked in the Space Race. It was a time of intense competition as both superpowers attempted to outmaneuver the other and become the first to achieve spaceflight, conduct crewed missions to orbit, and eventually land crews on another celestial body (i.e. the Moon).

*Albert II in preparation for his historic flight. Image Credit: NASA*

Before crewed missions could be sent, however, both the Soviet space program and NASA conducted rigorous tests involving animal test subjects, as a way of gauging the stresses and physical tolls going into space would have. These tests were not without precedent, as animals had been used for aeronautical tests in previous centuries.

For instance, in 1783, the Montgolfier brothers sent a sheep, a duck and a rooster when testing their hot air balloon to see what the effects would be. Between 1947-1960, the US launched several captured German V-2 rockets (which contained animal test subjects) to measure the effect traveling to extremely high altitudes would have on living organisms.

Because of the shortage of rockets, they also employed high-altitude balloons. These tests were conducted using fruit flies, mice, hamsters, guinea pigs, cats, dogs, frogs, goldfish and monkeys. The most famous test case was Albert II, a rhesus monkey that became the first monkey to go into space on June 14th, 1949.

For the Soviets, it was felt that dogs would be the perfect test subjects, and for several reasons. For one, it was believed that dogs would be more comfortable with prolonged periods of inactivity. The Soviets also selected female dogs (due to their better temperament) and insisted on stray dogs (rather than house dogs) because they felt they would be able to tolerate the extreme stresses of space flight better.

A safety module that was commonly used to send Russian "space dogs" into orbit. Credit: WIkipedia Commons/Bricktop/Russia in Space — *Image of the type of safety module that was used to send Russian “space dogs” into orbit. Credit: WIkipedia Commons/Bricktop/Russia in Space*

Training:

For the sake of preparing the dogs that were used for the sake of test flights, the Soviets confined the subjects in small boxes of decreasing size for periods of between 15 and 20 days at a time. This was designed to simulate spending time inside the small safety modules that would housed them for the duration of their flights.

Other exercises designed to get the dogs prepared for space flight included having them stand still for long periods of time. They also sought to get the dogs accustomed to wearing space suits, and made them ride in centrifuges that simulated the high acceleration experienced during launch.

Suborbital Flights:

Between 1951 and 1956, the Russians conducted their first test flights using dogs. Using R -1 rockets. a total of 15 missions were flown and were all suborbital in nature, reaching altitudes of around 100 km (60 mi) above sea level. The dogs that flew in these missions wore pressure suits with acrylic glass bubble helmets.

*Model of R-1 rocket at Znamensk City, near Kapustin Yar missile range. Credit: Wikipdia Commons/function.mil.ru*

The first to go up were Dezik and Tsygan, who both launched aboard an R-1 rocket on July 22nd, 1951. The mission flew to a maximum altitude of 110 km, and both dogs were recovered unharmed afterwards. Dezik made another sub-orbital flight on July 29th, 1951, with a dog named Lisa, although neither survived because their capsule’s parachute failed to deploy on re-entry.

Several more launches took place throughout the Summer and Fall of 1951, which included the successful launch and recovery of space dogs Malyshka and ZIB. In both cases, these dogs were substitutes for the original space dogs – Smelaya and Bolik – who ran away just before the were scheduled to launch.

By 1954, space dogs Lisa-2 (“Fox” or “Vixen”, the second dog to bear this name after the first died), Ryzhik (“Ginger” because of the color of her fur) made their debut. Their mission flew to an altitude of 100 km on June 2nd, 1954, and both dogs were recovered safely. The following year, Albina and Tsyganka (“Gypsy girl”) were both ejected out of their capsule at an altitude of 85 km and landed safely.

Between 1957 to 1960, 11 flights with dogs were made using the R-2A series of rockets, which flew to altitudes of about 200 km (124 mi). Three flights were made to an altitude of about 450 km (280 mi) using R-5A rockets in 1958. In the R-2 and R-5 rockets, the dogs were contained in a pressured cabin

*Photo of Otvazhnaya and the Mafrusha, two of the three brave cosmonauts who flew together on July 2nd, 1959. Credit: Wikipedia Commons (.ru)*

Those to take part in these launches included Otvazhnaya (“Brave One”) who made a flight on July 2nd, 1959, along with a rabbit named Marfusha (“Little Martha”) and another dog named Snezhinka (“Snowflake”). Otvazhnaya would go to make 5 other flights between 1959 and 1960.

Orbital Flights:

By the late 1950s, and as part of the Sputnik and Vostok programs, Russian dogs began to be sent into orbit around Earth aboard R-7 rockets. On November 3rd, 1957, the famous space dog Laika became the first animal to go into orbit as part of the Sputnik-2 mission. The mission ended tragically, with Laika dying in flight. But unlike other missions where dogs were sent into suborbit, her death was anticipated in advance.

It was believed Laika would survive for a full ten days, when in fact, she died between five and seven hours into the flight. At the time, the Soviet Union claimed she died painlessly while in orbit due to her oxygen supply running out. More recent evidence however, suggests that she died as a result of overheating and panic.

This was due to a series of technical problems which resulted from a botched deployment. The first was the damage that was done to the thermal system during separation, the second was some of the satellite’s thermal insulation being torn loose. As a result of these two mishaps, temperatures in the cabin reached over 40º C.

Animals in Space — *The famous space dog Laika, pictured here before her launch in 1957. Credit: AP Photo/NASA*

The mission lasted 162 days before the orbit finally decayed and it fell back to Earth. Her sacrifice has been honored by many countries through a series of commemorative stamps, and she was honored as a “hero of the Soviet Union”. Much was learned from her mission about the behavior of organisms during space flight, though it has been argued that what was learned did not justify the sacrifice.

The next dogs to go into space were Belka (“Squirrel”) and Strelka (“Little Arrow”), which took place on Aug. 19th, 1960, as part of the Sputnik-5 mission. The two dogs were accompanied by a grey rabbit, 42 mice, 2 rats, flies, and several plants and fungi, and all spent a day in orbit before returning safely to Earth.

Strelka went on to have six puppies, one of which was named Pushinka (“Fluffy”). This pup was presented to President John F. Kennedy’s daughter (Caroline) by Nikita Khrushchev in 1961 as a gift. Pushinka went on to have puppies with the Kennedy’s dog (named Charlie), the descendants of which are still alive today.

On Dec. 1st, 1960, space dogs Pchyolka (“Little Bee”) and Mushka (“Little Fly”) went into space as part of Sputnik-6. The dogs, along with another compliment of various test animals, plants and insects, spent a day in orbit. Unfortunately, all died when the craft’s retrorockets experienced an error during reentry, and the craft had to be intentionally destroyed.

The dogs Veterok and Ugoljok who took part in a scientific experiment, 22 day flight in space. Credit: Wikipedia Commons — *The dogs Veterok and Ugoljok, who spent 22 days in orbit as part of the Cosmos 110 mission. Credit: Wikipedia Commons/Tekniska museet*

Sputnik 9, which launched on March 9th, 1961, was crewed by spacedog Chernenko (“Blackie”) – as well as a cosmonaut dummy, mice and a guinea pig. The capsule made one orbit before returning to Earth and making a soft landing using a parachute. Chernenko was safely recovered from the capsule.

On March 25th, 1961, the dog Zvyozdocha (“Starlet”) who was named by Yuri Gagarin, made one orbit on board the Sputnik-10 mission with a cosmonaut dummy. This practice flight took place a day before Gagarin’s historic flight on April 12th, 1961, in which he became the first man to go into space. After re-entry, Zvezdochka safely landed and was recovered.

Spacedogs Veterok (“Light Breeze”) and Ugolyok (“Coal”) were launched on board a Voskhod space capsule on Feb. 22nd, 1966, as part of Cosmos 110. This mission, which spent 22 days in orbit before safely landing on March 16th, set the record for longest-duration spaceflight by dogs, and would not be broken by humans until 1971.

Legacy:

To this day, the dogs that took part in the Soviet space and cosmonaut training program as seen as heroes in Russia. Many of them, Laika in particular, were put on commemorative stamps that enjoyed circulation in Russia and in many Eastern Bloc countries. There are also monuments to the space dogs in Russia.

Laika, dog launched into space on stamp from Rumania Posta Romania , 1957. Credit: WIkipedia Commons — *Romanian commemorate stamp showing Laika, the first dog launched into space, from Rumania Posta, 1957. Credit: Wikipedia Commons*

These include the statue that exists outside of Star City, the Cosmonaut training facility in Moscow. Created in 1997, the monument shows Laika positioned behind a statue of a cosmonaut with her ears erect. The Monument to the Conquerors of Space, which was constructed in Moscow in 1964, includes a bas-relief of Laika along with representations of all those who contributed to the Soviet space program.

On April 11, 2008, at the military research facility in Moscow where Laika was prepped for her mission to space, officials unveiled a monument of her poised inside the fuselage of a space rocket (shown at top). Because of her sacrifice, all future missions involving dogs and other test animals were designed to be recoverable.

Four other dogs died in Soviet space missions, including Bars and Lisichka (who were killed when their R-7 rocket exploded shortly after launch). On July 28, 1960, Pchyolka and Mushka also died when their space capsule was purposely destroyed after a failed re-entry to prevent foreign powers from inspecting the capsule.

However, their sacrifice helped to advance safety procedures and abort procedures that would be used for many decades to come in human spaceflight.

We have written many interesting articles about animals and space flight here at Universe Today. Here’s Who was the First Dog to go Into Space?, What was the First Animal to go into Space?, What Animals Have been to Space?, Who was “Space Dog” Laika?, and Russian Memorial for Space Dog Laika.

For more information, check out Russian dogs lost in space and NASA’s page about the history of animals in space.

Astronomy Cast has an episode on space capsules.

Sources:

September 30, 2016October 3, 2016 by Matt Williams

What Does Earth Look like from Mars?

Image taken by the HiRISE camera on NASA's Mars Reconnaissance Orbiter, showing Earth and the Moon. Credit: NASA/JPL

Modern astronomy and space exploration has blessed us with a plethora of wonderful images. Whether they were images of distant planets, stars and galaxies taken by Earth-based telescopes, or close-ups of planets or moons in our own Solar System by spacecraft, there has been no shortage of inspiring pictures. But what would it look like to behold planet Earth from another celestial body?

We all remember the breathtaking photos taken by the Apollo astronauts that showed what Earth looked like from the Moon. But what about our next exploration destination, Mars? With all the robotic missions on or in orbit around the Red Planet, you’d think that there would have been a few occasions where they got a good look back at Earth. Well, as it turn out, they did!

Pictures from Space:

Pictures of Earth have been taken by both orbital missions and surface missions to Mars. The earliest orbiters, which were part of the Soviet Mars and NASA Mariner programs, began arriving in orbit around Mars by 1971. NASA’s Mariner 9 probe was the first to establish orbit around the planet’s (on Nov. 14, 1971), and was also the first spacecraft to orbit another planet.

*Image of Earth and Moon, taken by the Mars Orbiter Camera of Mars Global Surveyor on May 8 2003. Credit: NASA/JPL/Malin Space Science Systems*

The first orbiter to capture a picture of Earth from Mars, however, was the Mars Global Surveyor, which launched in Nov. 7th, 1996, and arrived in orbit around the planet on Sept. 12th, 1997. In the picture (shown above), which was taken in 2003, we see Earth and the Moon appearing closely together.

At the time the picture was taken, the distance between Mars and Earth was 139.19 million km (86.49 million mi; 0.9304 AU) while the distance between Mars and the Moon was 139.58 million km (86.73 million mi; 0.9330 AU). Interestingly enough, this is what an observer would see from the surface of Mars using a telescope, whereas a naked-eye observer would simply see a single point of light.

Usually, the Earth and Moon are visible as two separate points of light, but at this point in the Moon’s orbit they were too close to resolve with the naked eye from Mars. If you look closely at Earth, you can just make out the shape of South America.

*Earth and the Moon, captured by the Mars Express spacecraft on July 3, 2003. Credit: ESA*

The picture above was snapped by the Mars Express’s High Resolution Stereo Camera (HRSC) on the ESA’s Mars Express probe. It was also taken in 2003, and is similar in that it shows the Earth and Moon together. However, in this image, we see the two bodies at different points in their orbit – which is why the Moon looks like its farther away. Interestingly enough, this image was actually part of the first data sets to be sent by the spacecraft.

The next orbiter to capture an image of Earth from Mars was the Mars Reconnaissance Orbiter (MRO), which was launched in August of 2005 and attained Martian orbit on March 10th, 2006. When the probe reached Mars, it joined five other active spacecraft that were either in orbit or on the surface, which set a record for the most operational spacecraft in the vicinity of Mars at the same time.

In the course of its mission – which was to study Mars’ surface and weather conditions, as well as scout potential landing sites – the orbiter took many interesting pictures. The one below was taken on Oct. 3rd, 2007, which showed the Earth and the Moon in the same frame.

Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) camera can also be used to view other planets. MRO took this image of the Earth and the Moon on 3 October 2007. Credit: NASA/JPL — *Image of Earth and the Moon taken by the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE) on Oct. 3rd, 2007. Credit: NASA/JPL*

Pictures from the Surface:

As noted already, pictures of Earth have also been taken by robotic missions to the surface of Mars. This has been the case for as long as space agencies have been sending rovers or landers that came equipped with mobile cameras. The earliest rovers to reach the surface – Mars 2 and Mars 3– were both sent by the Soviets.

However, it was not until early March of 2004, while taking photographs of the Martian sky, that the Spirit rover became the first to snap a picture of Earth from the surface of another planet. This image was caught while the rover was attempting to observe Mars’ moon Deimos making a transit of the Sun (i.e. a partial eclipse).

This is something which happens quite often given the moon’s orbital period of about 30 hours. However, on this occasion, the rover managed to also capture a picture of distant Earth, which appeared as little more than a particularly bright star in the night sky.

Earth as seen from Mars, shortly before daybreak. This is the first image of the Earth from the surface of another planet. Credit: NASA/JPL — *Earth seen from Mars shortly before daybreak. This is the first image of the Earth from the surface of another planet. Credit: NASA/JPL*

The next rover to snap an image of Earth from the Martian surface was Curiosity, which began sending back many breathtaking photos even before it landed on Aug. 6th, 2012. And on Jan. 31st, 2014 – almost a year and a half into its mission – the rover managed to capture an image of both Earth and the Moon in the night sky.

In the image (seen below), Earth and the Moon are just visible as tiny dots to the naked eye – hence the inset that shows them blown up for greater clarity. The distance between Earth and Mars when Curiosity took the photo was about 160 million km (99 million mi).

Earth has been photographed from Mars several times now over the course of the past few decades. Each picture has been a reminder of just how far we’ve come as a species. It also provides us with a preview of what future generations may see when looking out their cabin window, or up at the night sky from other planets.

Image taken by NASA's Curiosity Mars rover, showing Earth and the Moon shining in the night sky. Credit: NASA/JPL — *Image taken by NASA’s Curiosity Mars rover, showing Earth and the Moon shining in the night sky. Credit: NASA/JPL*

We have written many interesting articles about Earth and Mars here at Universe Today. Here’s Incredible Image of Mars from Earth, Mars Compared to Earth, How Far is Mars from Earth, and How Long Does it Take to get to Mars?

For more information, be sure to check out NASA’s Solar System Exploration page on Mars.

Astronomy Cast also has an interesting episode on the subject – Episode 52: Mars

Sources:

September 29, 2016February 22, 2017 by Fraser Cain

Where Can I Take Off My Space Helmet?

It’s been a while since I read the NASA manual on space helmet operation, but if I recall correctly, they really just have one major rule. When you go to space, keep your space helmet on.

I don’t care what haunting music those beguiling space sirens are playing. It doesn’t matter if you’ve got a serious case of space madness, and you’re hallucinating that you’re back on your Iowa farm, surrounded by your loved ones. Even if you just turned on an ancient terraforming machine and you’re stumbling around the surface of Mars like an idiot. You keep your helmet on.

Not convinced? Well then, allow me to explain what happens if you decide to break that rule. Without a helmet, and your own personal Earth-like atmosphere surrounding you, you’ll be exposed to the hard vacuum of space.

Within a moment, all the air will rush out of your lungs, and then you’ll fall unconscious in about 45 seconds. Starved for oxygen, you’ll die of suffocation in just a couple of minutes. Then you’ll freeze solid and float about forever. Just another meat asteroid in the Solar System.

That’s the official stance on space helmet operation, but just between you and me, there might be a little wiggle room. A few other places in the Solar System where you can take your helmet off for just a moment, and maybe not die instantaneously.

Earth is obviously safe. If you’re down here on the planet, and you’re still wearing your helmet, you’re missing the whole point of why you need a helmet in the first place. That space helmet rule only applies to space, silly, you can take it off down here.

In order to survive, the human body needs a few things. First, we need pressure surrounding our body, and helping to keep our lungs inflated. The Earth’s atmosphere provides that service, stacking a huge column of air down on top of you.

Without enough pressure, the air will blast out of your lungs and you’ll suffocate. Too much pressure and your lungs will crush and your heart will give out.

You’re going to want atmospheric pressure somewhere between .5 to 5 times the atmosphere of Earth.

If you can’t find air, then some other gas or even water will do in a pinch. You can’t breathe it, but it can provide the pressure you’re looking for.

Do not take your helmet off on the Moon. Credit: NASA

If you’ve got the pressure right, then your next priority will be the temperature. You know what it’s like to be too cold on Earth, and too hot, so use your judgement here. It’s too cold if you’re starting to die of hypothermia, and too hot if you’re above 60 C for a few minutes.

If you really want to thrive, find air you can breathe. Ideally a nice mixture of nitrogen and oxygen. Again, here on Earth, that column of air pushing down on you also allows you to breathe. If you swapped air for carbon dioxide or water, you’re going to need to hold your breath.

So what are some other places in the Solar System that you could take your helmet off for a few brief moments?

Your best bet is the planet Venus. Not down at the surface, where the temperature is hot enough to melt lead, and it’s 90 atmospheres pressure.

But up in the cloud tops, it’s a whole different story. At 52.5 kilometers altitude, the temperature is about 37 C. A little stifling, but not too bad. And the air pressure is about 65% Earth’s air pressure.

Hold your breath if you’re planning on taking off your helmet within the clouds of Venus. Credit: NASA

The problem is that this region is right in the middle of Venus’ sulphuric acid cloud layer, so you might inhale a mist of toxic acid if you tried to breathe. Not to mention the fact that Venus’ atmosphere is carbon dioxide, which means you’ll asphyxiate if you tried to breathe it.

But assuming you had some kind of air supply to breathe, and a suit to protect you from the sulphuric acid, you could hang around, without a helmet as long as you liked.

Take that! Overly draconian NASA helmet rules.

Out on the surface of Titan? Good news! The surface pressure on Titan is 1.45 times that of Earth. You won’t need a pressure helmet at all, ever. You will need a warming helmet, however, since the temperature on Titan is -179 C. You might be able to take that helmet off for a brief moment, before your face freezes, but don’t take a breath, otherwise you’ll freeze your lungs.

Want another location? No problem. Astronomers are pretty sure there are vast reservoirs of water under the surface of many moons and large objects in the Solar System, from Europa to Charon.

This artist's concept of Jupiter's moon Ganymede, the largest moon in the solar system, illustrates the club sandwich model of its interior oceans. Credit: NASA/JPL — This artist’s concept of Jupiter’s moon Ganymede, the largest moon in the solar system, illustrates the club sandwich model of its interior oceans. You could try taking your helmet off while diving in them. Credit: NASA/JPL

They’re heated up through tidal interactions, and could be dozens of kilometers thick. Drill down through the ice sheet, and then just dive into the icy waters without a helmet. It’ll be really cold, and you won’t be able to breathe, but you can stay alive as long as you can hold your breath.

Did you jump out of your spacecraft and now you’re falling to your death into one of the Solar System’s gas giants? That’s bad news and it won’t end well. However, there’s a tiny silver lining. As you fall through the atmosphere of Jupiter, for example, there’ll be a moment when the temperature and pressure roughly match what your body can handle.

Go ahead and take your helmet off and enjoy that sweet spot before you plunge into the swirling hydrogen gas. Once again, though, don’t breathe. Hold your breath, the moment will last longer before you go unconscious.

And listen, if you really really need to take off your helmet in the cold vacuum of space, you can do it. Make sure you completely exhale so you don’t wreck your lungs. Then you’ve got about 45 seconds before you go unconscious.

That’s enough time to jump across to an open airlock, or kick that nasty xenomorph holding onto your leg into deep space.

Even though the NASA space helmet manual has one rule – keep your helmet on – you can see there are a few times and places where you can bend those rules without instantly dying. Use your judgement.

I’d like to thank Mechadense for posting a comment on an earlier Guide to Space YouTube video, which became the inspiration for this episode. Thanks for doing the math Mechadense and bringing the science.

September 28, 2016September 28, 2016 by Matt Williams

What is Carbon Dating?

Full length negatives of the shroud of Turin. Radiocarbon dating allowed for its true age to be determined. Credit: Wikipedia Commons

Here on Earth, Carbon is found in the atmosphere, the soil, the oceans, and in every living creature. Carbon 12 – aka. C-12, so-named because it has an atomic weight of 12 – is the most common isotope, but it is by no means the only one. Carbon 14 is another, an isotope of carbon that is produced when Nitrogen (N-14) is bombarded by cosmic radiation.

This process causes a proton to be displaced by a neutron, effectively turning atoms of Nitrogen it into an isotope of carbon – known as”radiocarbon”. It is naturally radioactive and unstable, and will therefore spontaneously decay back into N-14 over a period of time. This property makes it especially useful in a process known as “radiocarbon dating”, or carbon dating for short.

Origin of Radiocarbon:

Radiocarbon enters the biosphere through natural processes like eating and breathing. Plants and animals absorb both C-12 and C-14 in the course of their natural lifetimes simply by carrying out these basic functions. When they die, they cease to consume them, and the isotope of C-14 begins to revert back to its Nitrogen state at an exponential rate due to its radioactive decay.

Comparing the remaining C-14 of a sample to that expected from atmospheric C-14 allows the age of the sample to be estimated. In addition, scientists know that the half-life of radiocarbon is 5,730 years. This means that it takes a sample of radiocarbon 5,730 years for half of it to decay back into nitrogen.

After about 10 half-lives, the amount of radiocarbon left becomes too minuscule to measure and so this technique isn’t particularly reliable for dating specimens which died more than 60,000 years ago – i.e. during the late Middle Paleolithic (aka. Old Stone Age) period.

History of Development:

Experiments that would eventually lead to carbon dating began in the 1939s, thanks to the efforts of the Radiation Laboratory at the University of California, Berkeley. At the time, researchers were attempting to determine if any of the elements common to organic matter had isotopes with half-lives long enough to be of value in biomedical research.

By 1940, the half-life of Carbon 14 was determined, as was the mechanism through which it was created (slow neutrons interacting with Nitrogen in the atmosphere). This contradicted previous work, which held that it was the product of deuterium (H², or heavy hydrogen) and Carbon 13.

A hydrogen atom is made up of one proton and one electron, but its heavy form, called deuterium, also contains a neutron. HDO or heavy water is rare compared to normal drinking water, but being heavier, more likely to stick around when the lighter form vaporizes into space. Credit: NASA/GFSC — *A hydrogen atom is made up of one proton and one electron, but its heavy form, called deuterium, also contains a neutron. Credit: NASA/GFSC*

During World War II, Willard Libby – a chemist and graduate of Berkeley – read a paper by W. E. Danforth and S. A. Korff (published in 1939) which predicted that C 14 would be created in the atmosphere due to interactions between nitrogen and cosmic rays. From this, Libby came up with the idea of measuring the decay of C 14 as a method of dating organic material.

In 1945, Libby moved to the University of Chicago, where he began the work that would lead to the development of radiocarbon dating. In 1946, he published a paper in which he speculated that C 14 might exist within organic material alongside other carbon isotopes.

After conducting experiments, which measured C-14 in methane derived from sewage samples, Libby and his colleagues were able to demonstrate that organic matter contained radioactive C-14. This was followed by experiments involving wood samples for the tombs of two Egyptian kings, for which the age was known.

Their results proved accurate, with allowances for a small margin of error, and were published in 1949 in the journal Science. In 1960, Libby received the Nobel Prize in Chemistry for this work. Since that time, carbon dating has been used in multiple fields of science, and allowed for key transitions in prehistory to be dated.

*Diagram showing how radiocarbon dating works. Credit: howstuffworks.com*

Limits of Carbon Dating:

Carbon dating remains limited for a number of reasons. First, there is the assumption that the ratio of C-12 to C-14 in the atmosphere has remained constant, when in fact, the ratio can be affected by a number of factors. For instance, C-14 production rates in the atmosphere, which in turn are affected by the amount of cosmic rays penetrating the Earth’s atmosphere.

This is itself affected by things like the Earth’s magnetic field, which deflects cosmic rays. Furthermore, precise measurements taken over the last 140 years have shown a steady decay in the strength of the Earth’s magnetic field. This means there’s been a steady increase in radiocarbon production (which would increase the ratio).

Another limitation is that this technique can only be applied to organic material such as bone, flesh, or wood, and can’t be used to date rocks directly. On top of that, the addition of Carbon 12 will throw off the ration, thus leading to inaccurate assessments of a sample’s age.

This is where anthropogenic factors come into play. Since fossil fuels have no Carbon 14 content, the burning of gasoline, oil, and other hydrocarbons – and in greater and greater quantity over the course of the past century and a half – has diluted the C-14 content of the atmosphere.

On the other hand, atmospheric testing of nuclear weapons during the 1950s and 1960s is likely to have increased the Carbon 14 content of the atmosphere. In fact, research has been conducted which suggests that nuclear tests may have doubled the concentration of C-14 in this time, compared to natural production by cosmic rays.

Nevertheless, it remains the most accurate means of dating the scientific community has discovered so far. Until such time that another method becomes available – and one that produces smaller margins of error – it will remain the method of choice for archeology, paleontology, and other branches of scientific research.

We have written many articles about Carbon Dating for Universe Today. Here’s How Do We Know How Old Everything Is?, How Old is the Universe?, How Old is the Solar System?, How Long has Humans been on Earth?

If you’d like more info on Carbon Dating, check out NASA’s Virtual Dating: Isochron and Radiocarbon – Geology Labs On-line, and here’s a link to USGS Radiometric Dating Page.

We’ve also recorded an entire episode of Astronomy Cast all about How Carbon Dating Works. Here’s Episode 122: How Old is the Universe? and Episode 164: Inside the Atom.

Sources:

September 27, 2016February 22, 2017 by Fraser Cain

What is Absolute Zero?

Canadians don’t have much to be proud of, but we can regale you with our ability to withstand freezing cold temperatures. Now, I live on the West Coast, so I’m soft and weak, rarely experiencing temperatures below freezing.

But for some of my Canadian brethren, temperatures can dip down to levels your mind and body can scarcely comprehend. For example, I have a friend who lives in Winnipeg, Manitoba. For a day last winter, the temperatures there dipped down -31C, but with the windchill, it felt like -50C. On that same day, it was a balmy -29C on Mars. On Mars!

But for scientists, and the Universe, it can get much much colder. So cold, in fact, that they use a completely different temperature scale – Kelvin – to measure how far away things are from the coldest possible temperature: Absolute Zero.

Nowhere close to absolute zero. Credit: Osccarr (CC BY 2.0)

On the Celsius scale, Absolute Zero is -273.15 degrees. And in Fahrenheit, it’s -459.67 degrees. In the Kelvin scale, however, it’s very simple. Absolute Zero is 0 kelvin.

At this point, a science explainer is going to stumble into a minefield of incorrect usage. It’s not 0 degrees kelvin, you don’t say the degrees part, just the kelvin part. Just kelvin.

This is because when you measure something from an arbitrary point, like the direction you just turned, you’ve changed course 15-degrees. But if you’re measuring from an absolute point, like the lowest physical temperature defined by nature, you drop the degrees because it’s an absolute. An Absolute Zero.

Of course, I’ve probably gotten that wrong too. This stuff is hard.

Anyway, back to Absolute Zero.

Still not cold enough. Credit: Lori Cuthbert (CC BY 2.0)

Absolute Zero is the coldest possible temperature that can theoretically be reached. At this point, no heat energy can be extracted from a system, no work can be done. It’s dead Jim.

But it’s completely theoretical. It’s practically impossible to cool something down to Absolute Zero. In order to cool something down, you need to do work to extract heat from it. The colder you get, the more work you need to do. In order to get to Absolute Zero, you’d need to put in an infinite amount of work. And that’s ridiculous.

As you probably learned in physics or chemistry class, the temperature of a gas translates to the motion of the particles in the gas. As you cool a gas down, by extracting heat from it, the particles slow down.

You would think, then, that by cooling something down to Absolute Zero, all particle motion in that something would stop. But that’s not true.

From a quantum mechanics point of view, you can never know the position and momentum of particles at the same time. If the particles stopped, you’d know their momentum (zero) and their position… right there. The Universe and its laws of physics just can’t allow that to happen. Thank Heisenberg’s Uncertainty Principle.

Therefore, there’s always a little motion, even if you could get to Absolute Zero, which you can’t. But you can’t extract any more heat from it.

The physicist Robert Boyle was one of the first to consider the possibility that there was a lowest possible temperature, which he called the primum frigidum. In 1702, Guillaume Amontons created a thermometer that he calculated would bottom out at -240 C. Pretty close, actually.

But it was Lord Kelvin, who created this absolute scale in 1848, starting at -273 C, or 0 kelvin.

By this measurement, even with its windchill, Winnipeg was a balmy 223 kelvin on that wintry day.

The surface of Pluto, on the other hand varies from a low of 33 kelvin to a high of 55 kelvin. That’s -240 C to -218 C.

The average background temperature across the entire Universe is just 2.7 kelvin. You won’t find many places that cold, unless you get out to the vast cosmic voids that separate galaxy clusters.

Over time, the background temperature of the Universe will continue to drop, but it’ll never actually reach Absolute Zero. Even in a Googol years, when the last supermassive black hole has finally evaporated, and there’s no usable heat left in the entire Universe.

In fact, astronomers call this bleak future the “heat death” of the Universe. It’s heat death, as in, the death of all heat. And happiness.

You might be surprised to know that the coldest temperature in the entire Universe is right here on Earth. Well, sometimes, anyway. And assuming the aliens haven’t got better technology than us, which they probably do.

At the time that I’m recording this video, physicists have used lasers to cool down Rubidium-87 gas to just 170 nanokelvin, a tiny fraction above Absolute Zero. In fact, they won a Nobel Prize for their work in discovering Bose-Einstein condensates.

NASA is actually working on a new experiment called the Cold Atom Lab that will send a version of this technology to the International Space Station, where it should be able to cool material down to 100 picokelvin. That’s cold.

The Cold Atom Lab is planned to launch in August 2017. Credit: NASA / JPL

Here are your takeaways. Absolute Zero is the coldest possible temperature than can ever be reached, the point at which no further heat energy can be extracted from a system. Never say degrees kelvin, you’ll cause so much wincing. The Universe can’t match our cold generating abilities… yet. Take that Universe.

I’d love to hear the coldest temperature you’ve ever personally experienced. For me, it was visiting Buffalo in December. That’s not right.

September 27, 2016September 27, 2016 by Matt Williams

What is a Total Eclipse?

09 March 2016 - Total Solar Eclipse from Palu, Indonesia. Credit and copyright: Justin Ng.

Imagine if you will, that you are a human being living in prehistoric times. You look up at the sky and see the Sun slowly being blocked out, becoming a ominous black sphere that glows around the edges. Could you really be faulted for thinking that this was some sort of supernatural event, or that the end of the world was nigh?

Of course not. Which is why for thousands of years, human beings believed that solar eclipses were just that – a sign of death or a bad omen. But in fact, an eclipse is merely what happens when one stellar object passes in front of another and obscures it. In astronomy, this happens all the time; and between the Sun, the Moon, and the Earth, total eclipses have been witnessed countless times throughout history.

Definition:

The general term for when one body passes in front of another in a solar system is transit. This term accurately describes how, depending on your vantage point, stellar bodies pass in front of each other on a regular basis, thus causing the reflected light from that body to be temporarily obscured.

However, when we are talking about how the Moon can pass between the Earth and the Sun, and how the Earth can pass between the Sun and the Moon, we use the term eclipse. This is also known as a syzygy, an astronomical term derived from ancient Greek (meaning “yoked together”) that describes a straight-line configuration between three celestial bodies.

Total Solar Eclipse:

When the Moon passes between the Sun and the Earth, and the Moon fully occults (blocks) the Sun, it is known as the solar eclipse. The type of solar eclipse – total or partial – depends on the distance of the Moon from the Earth during the event.

During an eclipse of the Sun, only a thin path on the surface of the Earth is actually able to experience a total eclipse – which is called the path of totality. People on either side of that path see a partial eclipse, where the Sun is only partly obscured by the Moon, relative to those who are standing in the center and witnessing the maximum point of eclipse.

A total solar eclipse occurs when the Earth intersects the Moon’s umbra – i.e. the innermost and darkest part of its shadow. These are relatively brief events, generally lasting only a few minutes, and can only be viewed along a relatively narrow track (up to 250 km wide). The region where a partial eclipse can be observed is much larger.

https://www.flickr.com/photos/auraluu/7085004603/in/photolist-bN5v2M-dufbuU-pzUHQi-nZQkxQ-6KdhJ7-9TLjD4-dtvX13-pidJNx-dtvUxY-dxAA8r-n8uzjn-hx1CzU-du9zKv-c4eHhw-F1szSh-hx2yTc-dv7Y5W-dubgHK-du9zB6-FvPkNQ-drNyGZ-Eg3Msj-F4kfHb-zpuHFU-yUCmvN-yuSXP5-DqsCRp-zfU1bR-zbbFV9-FrtBYE-hdVRQm-rkh8fd-dufbHG-6KGxbK-dufbmf-du9zQe-ryZmAb-FtsHpn-EAUwcK-Ct6Fma-6KLF1b-FiThUB-EEgQjh-E8uHFM-yUC28b-rqtfQ3-yTR8jt-tsa14t-rHcxrz-rXwEhJ — *Totality! The view of the last total solar eclipse to cross a U.S. state (Hawaii) back in 1991. Credit and copyright: A. Nartist (shot from Cabo San Lucas, Baja California).*

During a solar eclipse, the Moon can sometimes perfectly cover the Sun because its size is nearly the same as the Sun’s when viewed from the Earth. This, of course, is an illusion brought on by the fact that the Moon is much closer to us than the Sun.

And since it is closer, it can block the light from the Sun and cast a shadow on the surface of the Earth. If you’re standing within that shadow, the Sun and the Moon appear to line up perfectly, so that the Moon is completely darkened.

After a solar eclipse reaches totality, the Moon will continue to move past the Sun, obscuring smaller and smaller portions of it and allowing more and more light to pass.

Total Lunar Eclipse:

A total eclipse of the Moon is a different story. In this situation, the entire Moon passes into the Earth’s shadow, darkening it fully. A partial lunar eclipse occurs when the shadow of the Earth doesn’t fully cover the Moon, so only part of the Moon is darkened.

Unlike a solar eclipse, a lunar eclipse can be observed from nearly anywhere in an entire hemisphere. In other words, observers all across planet Earth can see this darkening and it appears the same to all. For this reason, total lunar eclipses are much more common and easier to observe from a given location. A lunar eclipse also lasts longer, taking several hours to complete, with totality itself usually averaging anywhere from about 30 minutes to over an hour.

There are three types of lunar eclipses. There’s a penumbral eclipse, when the Moon crosses only the Earth’s penumbra (the region in which only a portion of light is obscured); followed by a partial, when the Moon crosses partially into the Earth’s umbra (where the light is completely blocked).

Last, there is a total eclipse, when the Moon crosses entirely into the Earth’s umbra. A total lunar eclipse involves the Moon passing through all three phases, then gradually passing out of the Earth’s shadow and becoming bright again. Even during a total lunar eclipse, however, the Moon is not completely dark.

Sunlight is still refracted through the Earth’s atmosphere and enters the umbra to provide faint illumination. Similar to what happens during a sunset, the atmosphere scatters shorter wavelength light, causing it to take on a red hue. This is where the phrase ‘Blood Moon‘ comes from.

Since the Moon orbits the Earth, you would expect to see an eclipse of the Sun and the Moon once a lunar month. However, this does not happen simply because the Moon’s orbit isn’t lined up with the Sun. In fact, the Moon’s orbit is tilted by a few degrees – 1.543º between the angle of the ecliptic and the lunar equator, to be exact.

This means that three objects only have the opportunity to line up and cause an eclipse a few times a year. It’s possible for a total of 7 solar and lunar eclipses every year, but that only happens a few times every century.

Other Types of Eclipses:

The term eclipse is most often used to describe a conjunction between the Earth, Sun and Moon. However, it can also refer to such events beyond the Earth–Moon system. For example, a planet moving into the shadow of one of its moons, a moon passing into the shadow of its host planet, or a moon passing into the shadow of another moon.

*Mosaic of Saturn seen in eclipse in September 2006. Earth is the bright dot just inside the F ring at upper left. (CICLOPS/NASA/JPL-Caltech/SSI)*

For instance, during the Apollo 12 mission in 1969, the crew was able to observe the Sun being eclipsed by the Earth. In 2006, during its mission to study Saturn, the Cassini spacecraft was able to capture the image above, which shows the gas giant transiting between the probe and the Sun.

In July of 2015, when the New Horizons mission passed through the shadow of Pluto, it was able to capture a stunning image of the dwarf planet eclipsing the Sun. The image was taken at a distance of about 2 million km (1.25 million miles), which provided the necessary vantage point to see the disc of the Sun become fully obscured.

On top of that, many other bodies in the Solar System can experience eclipses as well. These include the four gas giants, all of which have major moons that periodically transit between the planet and either Earth-based or space-based observatories.

The most impressive and common of these involve Jupiter and its four largest moons (Io, Europa, Ganymede and Callisto). Given the size and low axial tilt of these moons, they often experience eclipses with Jupiter as a result of transits, relative to our instruments.

An enviable view, of the most distant eclipse seen yet, as New Horizons flies through the shadow of Pluto. Image credit: NASA/JPL. — *An enviable view, of the most distant eclipse seen yet, as New Horizons flies through the shadow of Pluto. Credit: NASA/JPL.*

A well-known example occurred in April of 2014, when the Hubble Space Telescope caught an image of Ganymede passing in front at of Jupiter. At the time the image was taken, Ganymede was casting its shadow within Jupiter’s Great Red Spot, which lent the planet a cyclops-like appearance (see below).

The other three gas giants are known to experiences eclipses as well. However, these only occur at certain periods the planet’s orbit of the Sun, due to their higher inclination between the orbits of their moons and the orbital plane of the planets. For instance, Saturn’s largest moon Titan has been known to only occult the ringed gas giant once about every 15 years.

Pluto has also been known to experience eclipses with is largest moon (and co-orbiting body) Charon. However, in all of these cases, the eclipses are never total, as they do not have the size to obscure the much larger gas giant. Instead, the passage of the moons in front of the larger celestial bodies either cast small shadows on the cloud tops of the gas giants, or lead to an annular eclipse at most.

Similarly, on Mars, only partial solar eclipses are ever possible. This is because Phobos or Deimos are not large enough (or distant enough in their orbits) to cover the Sun’s disc, as seen from the surface of the planet. Phobos and Deimos have also been known to experience lunar eclipses as they slip into the shadow of Mars.

Jupiter's Great Red Spot and Ganymede's Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center) — Jupiter’s Great Red Spot and Ganymede’s Shadow. Image Credit: NASA/ESA/A. Simon (Goddard Space Flight Center)

Martian eclipses have been photographed numerous times from both the surface and from orbit. For example, in 2010, the Spirit rover captured images of a Martian lunar eclipse as Phobos, the larger of the two martian moons, was photographed while slipping into the shadow of Mars.

Also, between Nov. 4 and Nov. 5, 2010, the Opportunity rover captured several images (later turned into movies) of a Martian sunset. In the course of imaging the Sun for a total of 17 minutes, Opportunity captured stills of the Sun experiencing a solar eclipse. And on September 13th, 2012 – during the 37th day of its mission (Sol 27) – the Curiosity rover captured an image of Phobos transiting the Sun.

As far as astronomical events go, total eclipses (Lunar and Solar) are not uncommon occurrences. If you ever want to witness a one, all you need to do is keep track of when one will be visible from your part of the world. Some good resources for this are NASA’s Eclipse Website and timeanddate.com.

Or, if you’re the really adventurous type, you can find out where on Earth the next path of totality is going to be, and then book a vacation to go there. Get to the right spot at the right time, and you should be getting the view of a lifetime!

We have written many articles about the eclipse for Universe Today. Here’s a list of articles about specific times when a total Lunar Eclipse took place, and here’s a list of Solar Eclipse articles. And be sure to check out this article and video of an Annular Eclipse.

If you’d like more info about the Eclipse, check out NASA Homepage, and here’s a link to NASA’s Solar System Simulator.

We’ve also recorded related episodes of Astronomy Cast about Eclipses. Listen here, Episode 160: Eclipses.

Sources:

September 25, 2016September 25, 2016 by Matt Williams

How Can You see the Northern Lights?

Aurora borealis in Fairbanks, AK. on Monday night March 16. Credit: John Chumack

The Northern Lights have fascinated human beings for millennia. In fact, their existence has informed the mythology of many cultures, including the Inuit, Northern Cree, and ancient Norse. They were also a source of intense fascination for the ancient Greeks and Romans, and were seen as a sign from God by medieval Europeans.

Thanks to the birth of modern astronomy, we now know what causes both the Aurora Borealis and its southern sibling – Aurora Australis. Nevertheless, they remain the subject of intense fascination, scientific research, and are a major tourist draw. For those who live north of 60° latitude, this fantastic light show is also a regular occurrence.

Causes:

Aurora Borealis (and Australis) is caused by interactions between energetic particles from the Sun and the Earth’s magnetic field. The invisible field lines of Earth’s magnetoshere travel from the Earth’s northern magnetic pole to its southern magnetic pole. When charged particles reach the magnetic field, they are deflected, creating a “bow shock” (so-named because of its apparent shape) around Earth.

However, Earth’s magnetic field is weaker at the poles, and some particles are therefore able to enter the Earth’s atmosphere and collide with gas particles in these regions. These collisions emit light that we perceive as wavy and dancing, and are generally a pale, yellowish-green in color.

The variations in color are due to the type of gas particles that are colliding. The common yellowish-green is produced by oxygen molecules located about 100 km (60 miles) above the Earth, whereas high-altitude oxygen – at heights of up to 320 km (200 miles) – produce all-red auroras. Meanwhile, interactions between charged particles and nitrogen will produces blue or purplish-red auroras.

Variability:

The visibility of the northern (and southern) lights depends on a lot of factors, much like any other type of meteorological activity. Though they are generally visible in the far northern and southern regions of the globe, there have been instances in the past where the lights were visible as close to the equator as Mexico.

In places like Alaska, Norther Canada, Norway and Siberia, the northern lights are often seen every night of the week in the winter. Though they occur year-round, they are only visible when it is rather dark out. Hence why they are more discernible during the months where the nights are longer.

The magnetic field and electric currents in and around Earth generate complex forces that have immeasurable impact on every day life. The field can be thought of as a huge bubble, protecting us from cosmic radiation and charged particles that bombard Earth in solar winds. It’s shaped by winds of particles blowing from the sun called the solar wind, the reason it’s flattened on the “sun-side” and swept out into a long tail on the opposite side of the Earth. Credit: ESA/ATG medialab — The magnetic field and electric currents in and around Earth generate complex forces, and also lead to the phenomena known as aurorae. Credit: ESA/ATG medialab

Because they depend on the solar wind, auroras are more plentiful during peak periods of activity in the Solar Cycle. This cycle takes places every 11 years, and is marked by the increase and decrease of sunspots on the sun’s surface. The greatest number of sunspots in any given solar cycle is designated as a “Solar Maximum“, whereas the lowest number is a “Solar Minimum.”

A Solar Maximum also accords with bright regions appearing in the Sun’s corona, which are rooted in the lower sunspots. Scientists track these active regions since they are often the origin of eruptions on the Sun, such as solar flares or coronal mass ejections.

The most recent solar minimum occurred in 2008. As of January 2010, the Sun’s surface began to increase in activity, which began with the release of a lower-intensity M-class flare. The Sun continued to get more active, culminating in a Solar Maximum by the summer of 2013.

Locations for Viewing:

The ideal places to view the Northern Lights are naturally located in geographical regions north of 60° latitude. These include northern Canada, Greenland, Iceland, Scandinavia, Alaska, and Northern Russia. Many organizations maintain websites dedicated to tracking optimal viewing conditions.

The camera recorded pale purple and red but the primary color visible to the eye was green. Credit: Bob Kin — *An image captured of the northern lights, which appear pale purple and red, though the primary color visible to the eye was green. Credit: Bob Kin*

For instance, the Geophysical Institute of the University of Alaska Fairbanks maintains the Aurora Forecast. This site is regularly updated to let residents know when auroral activity is high, and how far south it will extend. Typically, residents who live in central or northern Alaska (from Fairbanks to Barrow) have a better chance than those living in the south (Anchorage to Juneau).

In Northern Canada, auroras are often spotted from the Yukon, the Northwest Territories, Nunavut, and Northern Quebec. However, they are sometimes seen from locations like Dawson Creek, BC; Fort McMurry, Alberta; northern Saskatchewan and the town of Moose Factory by James Bay, Ontario. For information, check out Canadian Geographic Magazine’s “Northern Lights Across Canada“.

The National Oceanic and Atmospheric Agency also provides 30 minute forecasts on auroras through their Space Weather Prediction Center. And then there’s Aurora Alert, an Android App that allows you to get regular updates on when and where an aurora will be visible in your region.

Understanding the scientific cause of auroras has not made them any less awe-inspiring or wondrous. Every year, countless people venture to locations where they can be seen. And for those serving aboard the ISS, they got the best seat in the house!

Speaking of which, be sure to check out this stunning NASA video which shows the Northern Lights being viewed from the ISS:

We have written many interesting articles about Auroras here at Universe Today. Here’s The Northern and Southern Lights – What is an Aurora?, What is the Aurora Borealis?, What is the Aurora Australis?, What Causes the Northern Lights?, How Does the Aurora Borealis Form?, and Watch Fast and Furious All-sky Aurora Filmed in Real Time.

For more information, visit the THEMIS website – a NASA mission that is currently studying space weather in great detail. The Space Weather Center has information on the solar wind and how it causes aurorae.

Astronomy Cast also has episodes on the subject, like Episode 42: Magnetism Everywhere.

Sources:

September 24, 2016December 5, 2016 by Matt Williams

What is a Debris Flow?

Landslides constitute one of the most destructive geological hazards in the world today. One of the main reasons for this is because of the high speeds that slides can reach, up to 160 km/hour (100 mph). Another is the fact that these slides can carry quite a bit of debris with them that serve to amplify their destructive force.

Taken together, this is what is known as a Debris Flow, a natural hazard that can take place in many parts of the world. A single flow is capable of burying entire towns and communities, covering roads, causing death and injury, destroying property and bringing all transportation to a halt. So how do we deal with them?

Definition:

A Debris Flow is basically a fast-moving landslide made up of liquefied, unconsolidated, and saturated mass that resembles flowing concrete. In this respect, they are not dissimilar from avalanches, where unconsolidated ice and snow cascades down the surface of a mountain, carrying trees and rocks with it.

Images of a Debris Flow Chute and Deposit, taken by the Arizona Geological Survey (AZGS). Credit: azgs.com — Images of a Debris Flow Chute
and Deposit, taken by the Arizona Geological Survey (AZGS). Credit: azgs.com

A common misconception is to confuse debris flows with landslides or mudflows. In truth, they differ in that landslides are made up of a coherent block of material that slides over surfaces. Debris flows, by contrast, are made up of “loose” particles that move independently within the flow.

Similarly, mud flows are composed of mud and water, whereas debris flows are made up larger particles. All told, it has been estimated that at least 50% of the particles contained within a debris flow are made-up of sand-sized or larger particles (i.e. rocks, trees, etc).

Types of Flows:

There are two types of debris flows, known as Lahar and Jökulhlaup. The word Lahar is Indonesian in origin and has to do with flows that are related to volcanic activity. A variety of factors may trigger a lahar, including melting of glacial ice due to volcanic activity, intense rainfall on loose pyroclastic material, or the outbursting of a lake that was previously dammed by pyroclastic or glacial material.

Jökulhlaup is an Icelandic word which describes flows that originated from a glacial outburst flood. In Iceland, many such floods are triggered by sub-glacial volcanic eruptions, since Iceland sits atop the Mid-Atlantic Ridge. Elsewhere, a more common cause of jökulhlaups is the breaching of ice-dammed or moraine-dammed lakes.

Debris flow channel in Ladakh, NW Indian Himalaya, produced in the storms of August 2010. Credit: Wikipedia Commons/DanHobley — *Debris flow channel in Ladakh, near the northwestern Indian Himalaya, produced in the storms of August 2010. Credit: Wikipedia Commons/DanHobley*

Such breaching events are often caused by the sudden calving of glacier ice into a lake, which then causes a displacement wave to breach a moraine or ice dam. Downvalley of the breach point, a jökulhlaup may increase greatly in size by picking up sediment and water from the valley through which it travels.

Causes of Flows:

Debris flows can be triggered in a number of ways. Typically, they result from sudden rainfall, where water begins to wash material from a slope, or when water removed material from a freshly burned stretch of land. A rapid snowmelt can also be a cause, where newly-melted snow water is channeled over a steep valley filled with debris that is loose enough to be mobilized.

In either case, the rapidly moving water cascades down the slopes and into the canyons and valleys below, picking up speed and debris as it descends the valley walls. In the valley itself, months’ worth of built-up soil and rocks can be picked up and then begin to move with the water.

As the system gradually picks up speed, a feedback loop ensues, where the faster the water flows, the more it can pick up. In time, this wall begins to resemble concrete in appearance but can move so rapidly that it can pluck boulders from the floors of the canyons and hurl them along the path of the flow. It’s the speed and enormity of these carried particulates that makes a debris flow so dangerous.

*Deforestation (like this clearcut in Sumatra, Indonesia) can result in debris flows. Credit: worldwildlife.org*

Another major cause of debris flows is the erosion of steams and riverbanks. As flowing water gradually causes the banks to collapse, the erosion can cut into thick deposits of saturated materials stacked up against the valley walls. This erosion removes support from the base of the slope and can trigger a sudden flow of debris.

In some cases, debris flows originate from older landslides. These can take the form of unstable masses perched atop a steep slope. After being lubricated by a flow of water over the top of the old landslide, the slide material or erosion at the base can remove support and trigger a flow.

Some debris flows occur as a result of wildfires or deforestation, where vegetation is burned or stripped from a steep slope. Prior to this, the vegetation’s roots anchored the soil and removed absorbed water. The loss of this support leads to the accumulation of moisture which can result in structural failure, followed by a flow.

Sarychev volcano, (located in Russia's Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Credit: NASA — *Sarychev volcano, (located in Russia’s Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Credit: NASA*

A volcanic eruption can flash melt large amounts of snow and ice on the flanks of a volcano. This sudden rush of water can pick up ash and pyroclastic debris as it flows down the steep volcano and carry them rapidly downstream for great distances.

In the 1877 eruption of Cotopaxi Volcano in Ecuador, debris flows traveled over 300 kilometers down a valley at an average speed of about 27 kilometers per hour. Debris flows are one of the deadly “surprise attacks” of volcanoes.

Prevention Methods:

Many methods have been employed for stopping or diverting debris flows in the past. A popular method is to construct debris basins, which are designed to “catch” a flow in a depressed and walled area. These are specifically intended to protect soil and water sources from contamination and prevent downstream damage.

Some basins are constructed with special overflow ducts and screens, which allow the water to trickle out from the flow while keeping the debris in place, while also allowing for more room for larger objects. However, such basins are expensive, and require considerable labor to build and maintain; hence why they are considered an option of last resort.

Aerial view of debris-flow deposition resulting in widespread destruction on the Caraballeda fan of the Quebrada San Julián. Credit: US Geological Survey — *Aerial view of the destruction caused by a debris-flow in the Venezuelan town of Caraballeda. Credit: US Geological Survey*

Currently, there is no way to monitor for the possibility of debris flow, since they can occur very rapidly and are often dependent on cycles in the weather that can be unpredictable. However, early warning systems are being developed for use in areas where debris flow risk is especially high.

One method involves early detection, where sensitive seismographs detect debris flows that have already started moving and alert local communities. Another way is to study weather patterns using radar imaging to make precipitation estimates – using rainfall intensity and duration values to establish a threshold of when and where a flows might occur.

In addition, replanting forests on hillsides to anchor the soil, as well as monitoring hilly areas that have recently suffered from wildfires is a good preventative measure. Identifying areas where debris flows have happened in the past, or where the proper conditions are present, is also a viable means of developing a debris flow mitigation plan.

We have written many articles about landslides for Universe Today. Here’s Satellites Could Predict Landslides, Recent Landslide on Mars, More Recent Landslides on Mars, Landslides and Bright Craters on Ceres Revealed in Marvelous New Images from Dawn.

If you’d like more info on debris flow, check out Visible Earth Homepage. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Sources:

September 23, 2016February 22, 2017 by Fraser Cain

How Can We Save The Sun?

Remember the movie Sunshine, where astronomers learn that the Sun is dying? So a plucky team of astronauts take a nuclear bomb to the Sun, and try to jump-start it with a massive explosion. Yeah, there’s so much wrong in that movie that I don’t know where to start. So I just won’t.

Seriously, a nuclear bomb to cure a dying Sun?

Here’s the thing, the Sun is actually dying. It’s just that it’s going to take about another 5 billion years to run of fuel in its core. And when it does, Cillian Murphy won’t be able to restart it with a big nuke.

But the Sun doesn’t have to die so soon. It’s made of the same hydrogen and helium as the much less massive red dwarf stars. And these stars are expected to last for hundreds of billions and even trillions of years.

Is there anything we can do to save the Sun, or jump-start it when it runs out of fuel in the core?

First, let me explain the problem. The Sun is a main sequence star, and it measures 1.4 million kilometers across. Like ogres and onions, the Sun is made of layers.

The interior structure of the Sun. Credit: Wikipedia Commons/kelvinsong

The innermost layer is the core. That’s the region where the temperature and pressure is so great that atoms of hydrogen are mashed together so tightly they can fuse into helium. This fusion reaction is exothermic, which means that it gives off more energy than it consumes.

The excess energy is released as gamma radiation, which then makes its way through the star and out into space. The radiation pushes outward, and counteracts the inward force of gravity pulling it together. This balance creates the Sun we know and love.

Outside the core, temperatures and pressures drop to the point that fusion can no longer happen. This next region is known as the radiative zone. It’s plenty hot, and the photons of gamma radiation generated in the core of the Sun need to bounce randomly from atom to atom, maybe for hundreds of thousands of years to finally escape. But it’s not hot enough for fusion to happen.

Outside the radiative zone is the convective zone. This is where the material in the Sun is finally cool enough that it can move around like a lava lamp. Hot blobs of plasma pick up enormous heat from the radiative zone, float up to the surface of the Sun, release their heat and then sink down again.

The only fuel the Sun can use for fusion is in the core, which accounts for only 0.8% of the Sun’s volume and 34% of its mass. When it uses up that hydrogen in the core, it’ll blow off its outer layers into space and then shrink down into a white dwarf.

The radiative zone acts like a wall, preventing the mixing convective zone from reaching the solar core.

If the Sun was all convective zone, then this wouldn’t be a problem, it would be able to go on mixing its fuel, using up all its hydrogen instead of this smaller fraction. If the Sun was more like a red dwarf, it could last much longer.

GJ1214b, shown in this artist’s view, is a super-Earth orbiting a red dwarf star 40 light-years from Earth. Credit: NASA, ESA, and D. Aguilar (Harvard-Smithsonian Center for Astrophysics) — Red dwarf stars burn for much longer than our Sun. Credit: NASA, ESA, and D. Aguilar (Harvard-Smithsonian Center for Astrophysics)

In order to save the Sun, to help it last longer than the 5 billion years it has remaining, we would need some way to stir up the Sun with a gigantic mixing spoon. To get that unburned hydrogen from the radiative and convective zones down into the core.

One idea is that you could crash another star into the Sun. This would deliver fresh fuel, and mix up the Sun’s hydrogen a bit. But it would be a one time thing. You’d need to deliver a steady stream of stars to keep mixing it up. And after a while you would accumulate enough mass to create a supernova. That would be bad.

But another option would be to strip material off the Sun and create red dwarfs. Stars with less than 35% the mass of the Sun are fully convective. Which means that they don’t have a radiative zone. They fully mix all their hydrogen fuel into the core, and can last much longer.

Imagine a future civilization tearing the Sun into 3 separate stars, each of which could then last for hundreds of billions of years, putting out only 1.5% the energy of the Sun. Huddle up for warmth.

But if you want to take this to the extreme, tear the Sun into 13 separate red dwarf stars with only 7.5% the mass of the Sun. These will only put out .015% the light of the Sun, but they’ll sip away at their hydrogen for more than 10 trillion years.

Stick the Earth in the middle and you'd have some very odd sunsets, not to mention orbital dynamics. Created with Universe Sandbox ² — Stick the Earth in the middle and you’d have some very odd sunrises and sunsets, not to mention orbital dynamics. Created with Universe Sandbox ²

But how can you get that hydrogen off the Sun? Lasers, of course. Using a concept known as stellar lifting, you could direct a powerful solar powered laser at a spot on the Sun’s surface. This would heat up the region, and generate a powerful solar wind. The Sun would be blasting its own material into space. Then you could use magnetic fields or gravity to direct the outflows and collect them into other stars. It boggles our imagination, but it would be a routine task for Type III Civilization engineers on star dismantling duty.

So don’t panic that our Sun only has a few billion years of life left. We’ve got options. Mind bendingly complicated, solar system dismantling options. But still… options.