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Gamma-Ray Bursts
by Gary Strawn
27 February 2012

Note:  The following has nothing to do with Kona coffee, nothing to do with farming and nothing to do with anything about Kona Earth.  It is simply a subject I found interesting so I decided to write about it.  Maybe you can enjoy the story while sipping a nice cup of coffee.

Trinity
Trinity Test:  16 milliseconds after
humans entered the Atomic Age.
Source: Los Alamos National Laboratory
Nuclear Weapons
On July 16, 1945 at 05:29:45 Mountain War Time, a quiet corner of a remote desert in New Mexico became very suddenly and very violently unquiet as the world entered the Atomic Age.  The Trinity test (video) was the culmination of the Manhattan Project and the world's first detonation of a nuclear device.  Observers had set up a betting pool with predictions ranging from complete dud to incineration of the entire planet.  Actual yield was about twenty thousand tons of TNT with a fireball that reached 40,000 feet high.  Immediately after the massive explosion, the project director turned to Oppenheimer and said "Now we are all sons of bitches."

A mere three weeks later, the world's first nuclear bomb was detonated over Hiroshima, Japan and three days later a second nuclear bomb was dropped on Nagasaki, Japan.  Approximately 200,000 people were killed by these two bombs.  It was the end of World War II but just the beginning of the nuclear arms race.

Bikini
Thermonuclear test at Bikini Atoll.
The full resolution image is spectacular.
Source: Wikipedia, U.S. Department of Defense
The Soviet Union detonated their first nuclear test device a few years later in 1949.  A few years after that, in 1952, the United States started testing thermonuclear bombs.  These large hydrogen fusion bomb make atomic fission bombs look like mere firecrackers.  Spectacular footage (video) from Operation Crossroads shows large ships dwarfed by the giant explosion.  The crater is still visible today.  This testing made the previously obscure Bikini Atoll world famous.  Of course the word Bikini lives on for other reasons too.

In 1961 the Soviet Union detonated Tsar Bomba, creating the largest ever thermonuclear explosion.  Compared to the 15 kiloton blast in Hiroshima, Tsar Bomba's 50 megaton (50,000 kiloton) blast was absolutely massive.  It was originally built to be twice as powerful but later decided that 100 megatons was too much to test "safely."  A 100 megaton blast would certainly have destroyed the plane that delivered it, not to mention the damage to Soviet civilians from radioactive fallout.  Even at half capacity, the shock wave from Tsar Bomba was so large that it made three laps around the Earth.  Everybody nodded their heads in agreement that it was a big boom.

Some mood music
"Russians" by Sting
On October 7, 1963, President John F. Kennedy signed the Nuclear Test Ban Treaty.  The test ban was definitely a turning point but it did not end nuclear testing.  China didn't even start testing until the year after the ban.  It was nearly 30 years before the Soviet Union and United States stopped testing.  The United Kingdom, France, India, Pakistan and probably Israel and South Africa have all conducted nuclear tests.  North Korea insists on their right to nuclear weapons, testing publicly as recently as 2009 and possibly covertly since then.  Iran may not be far behind.

Tsar Bomba
Tsar Bomba is the largest nuclear bomb ever detonated.
The U.S. has a special plane, the WC-135 Constant Phoenix, that can detect and identify nuclear explosions.  It does this by "sniffing" the air for xenon isotopes that are created by a nuclear event.  Seismographs are also used to detect the location and size of a detonation.  It doesn't matter if the bomb is set off in the air, underground or underwater, chances are good that it will be detected.  But what about nuclear bombs in space?

EMP
As it turns out, nuclear detonations in Earth orbit are particularly easy to detect because they seriously mess with the Earth's magnetic fields.  In fact, the electro-magnetic pulse (EMP) from a nuclear detonation can be far more devastating than the explosion itself.  There are all sorts of horror stories, fiction and non-fiction, about EMPs and the resulting havoc.

In 1962, the year before the Nuclear Test Ban Treaty, the U.S. government decided to test the effects of a nuclear bomb generated EMP.  Starfish Prime was a 1.44 megaton thermonuclear warhead that would be detonated in low Earth orbit (250 miles) over Johnston Island in the Pacific.  The event was advertised ahead of time as an "Atomic Rainbow Over Honolulu."  Many people planned rooftop "rainbow bomb" parties since it sounded like a great way to view the event.  Conveniently scheduled for 11pm Honolulu time, there was plenty of opportunity to have a few beers first.

Starfish Prime
The Starfish Prime test lit up a large part of the Pacific Ocean.
Sure enough, at nine seconds after 11, the skies lit up.  The gamma-ray burst from the bomb grabbed the Earth's magnetic field and shook violently, creating a temporary Van Allen radiation belt.  The resulting EMP was far stronger than expected, so strong that many of the test instruments were unable to properly measure the blast.  The aurora was spectacular and a large area of the Pacific was lit up as bright as day.  Nearly a thousand miles away, the folks sitting on their roofs in Hawaii experienced power outages and electical damage.  There is an interesting NPR video about Starfish Prime with some great footage.  Unfortunately, all footage of inebriated Hawaiians quickly climbing down from their rooftops has been lost.

In addition to its unexpectedly strong effects, further study showed that the Starfish Prime blast would have caused even more damage if it had occurred over the continental United States.  With all of our delicate modern electronics, such a blast today could cause a huge amount of destruction and chaos.  Not many electronic car ignitions, Internet servers or iPhones are designed to withstand an EMP attack.

More mood music
"War" by Frankie
Goes to Hollywood
With the Nuclear Test Ban Treaty in place, we probably won't have any more opportunities to sit in our lawn chairs and watch EMP's from over the horizon.  At least not from officially scheduled nuclear tests.  It's the unexpected detonations that are most distressing.  It is for this reason that government espionage and surveillance efforts are often well funded.

Project Vela
The nuclear arms race was "the focus of a massive intelligence effort..."  There were spies on the Roof of the World and the Bottom of the Sea (video).  There were even concerns about spies on the far side of the moon.  It may sound absurd now but after an America U-2 spy plane took pictures of a nuclear missile base being built in Cuba, tensions were high and suspicions prevailed.  Watching for covert nuclear testing in space was a project that had little difficulty finding prompt and ample funding.

Vela Satellites
The Vela Satellites were designed to watch for nuclear explosions in space.
On October 17, 1963, ten days after Kennedy's test ban treaty went into effect, the U.S. Air Force launched the first Vela satellite pair, one satellite for each side of the Earth.  Future Vela satellites used cleverly named Bhangmeters to look for the tell-tale double flash of nuclear explosions in the atmosphere.  This double flash is reliable for atmospheric detonations but early Vela satellites were primarily concerned with detecting detonations in space.  The first Vela satellites used x-ray, gamma-ray and neutron detectors that were crude by modern standards yet proved surprisingly effective.  Orbiting at a very high 63,000 miles, they could even detect explosions behind the moon.

Sure enough, a few years after launch, the Vela satellites did indeed detect an unexplained flash of gamma radiation.  Solar flares and other known phenomenon were quickly ruled out yet the data didn't match the signature of any known nuclear weapons either.  Luckily the Vela team did not panic and announce that the Russians were attacking with some sort of secret new weapon.  Instead, they quietly filed away the classified data for later study.  They hoped that it was just some sort of unexpected sensor error or obscure natural phenomenon.


Of Cosmic Origin
In the following years, these unexplained gamma-ray bursts continued to occur.  The detectors were not sophisticated enough to determine the location of the events.  They could have been from behind the moon or from anywhere else in the sky.  It wasn't until years later that future satellites with better detectors were able to determine that the flashes were definitely "of cosmic origin."  Nobody knew what caused them, just that they weren't from the Earth, Moon or Sun.

In 1973, the unexplained Vela data was finally declassified and a paper was published that discussed 16 different cosmic gamma-ray bursts.  This was the first time the astronomical community was alerted to the existence of cosmic gamma-ray bursts.  Much study ensued.

The explanation of these gamma-ray bursts (GRB) proved decidedly elusive.  The first problem is that gamma-rays do not easily penetrate the atmosphere so GRB detectors work best when located on a satellite.  In the early 1970's, there were not many satellites with GRB detectors on them.

Obligatory
space music
The next problem, even more troublesome, is that gamma-rays can not be focused into a visible image with a telescope.  A gamma-rays detector is more like a Geiger counter that simply clicks whenever something is detected.  If you have multiple detectors, each one located on a different satellite located very far apart, and you measure the timing of the clicks extremely accurately, then it is possible to roughly triangulate on the approximate direction of the GRB.  Satellites in orbit are too close to each other, it's really best to have gamma-ray detectors spread across the solar system.  Even then, it's difficult to get an accurate location.

To make matters worse, data from GRB detectors required days or weeks to process but a GRB flash lasts only seconds.  By the time a telescope could be pointed in the right direction there was nothing there to see.  All sorts of theories were tested but nobody could find any other object or phenomenon consistently associated with GRBs.  Despite dauntless debate and steady study, little progress was made.  If only there was some way to get more data.

BATSE
GRBs are distributed evenly across the sky.
Source: NASA BATSE
In a galaxy far, far away
In 1991, nearly 20 years since the mystery began, the Space Shuttle Atlantis (STS-37) placed the Compton Gamma-Ray Observatory into orbit.  It had a fancy new gamma-ray detector (BATSE) specifically designed to search for gamma-ray bursts.  The detector did its job wonderfully, detecting bursts about once per day.  Unfortunately, by providing so much new data and answering a few questions, it just made the mystery bigger.

It was shown that GRBs are isotropic.  In other words, they are evenly distributed across the sky.  That seems like no big deal until you consider that neither the solar system nor the galaxy are isotropic.  Both are flattened disks and we are inside these disks.  Imagine standing on a giant Frisbee.  Look sideways and you see the Frisbee but look up and you see nothing.  That's why the early Egyptians thought the Milky Way looked kind of like the Nile River running across the sky and also why the planets always lie along the plane of the zodiac.

Since the GRBs were appearing everywhere across the sky, that meant that they were not all on our Frisbee.  It meant that GRBs must either be from some completely unobserved, unexplained local phenomenon or they must be from far, far away in distant galaxies.  Neither choice made sense and much debate ensued.

GRB 970228
GRB 970228 - First observation of the afterflow of a GRB and its galaxy.
Source: NASA Hubble
With several thousand different GRBs to explain, it seemed  unlikely that nearby stars were the source.  Yet distant galaxies didn't make sense either because of the inverse-square law.  The brightness of a GRB is inversely proportional to the square of the distance so if a GRB is from another galaxy then it must be very, very bright.  Like totally mind-boggling, impossibly stupid bright.

In 1997 on February 28 (GRB 970228), after many years of stubbornly refusing to give up and accept ignorance, astronomers finally managed to observe the afterglow of a GRB.  This afterglow coincided with a galaxy that is about 8.1 billion light years away.  That is very far away.  At such a distance the GRB would need to emit more energy than anybody could explain.

As Einstein stated, energy is equal to mass times the speed of light squared (E=mc²) so a GRB would require the instant and complete conversion of two solar masses.  The sun is a big object with a lot of mass.  The speed of light squared is also a rather sizable number.  Multiply the two together and you get, well, a lot of energy.  Despite what the math says, no known mechanism can create so much energy so quickly.  It looked like the GRB was in the distant galaxy but maybe it was just in front of it and actually much closer to us.

A couple months later the red shift from GRB 970508 was recorded by the W. M. Keck Observatory in Hawaii.  Astronomers can use the red shift to measure an object's distance.  The GRB's red shift showed a distance of 6 billion light years, more concretely proving that GRBs were indeed from distant galaxies.  Now the only problem was figuring out what could create such ludicrous amounts of energy.

Your Mama is soooo big
No known process in the Universe can produce enough energy to create a GRB from a spherical explosion.  The sun will barely put out that much energy over it's entire lifetime yet a GRB can produce that much energy in seconds.  It seems impossible unless, possibly, the explosion is focused into a tight beam.

A lawn sprinkler gently spreads water in all directions.  Squeeze that same amount of water through a small nozzle and you get a much more powerful stream.  If GRBs are a narrow beam instead of an isotropic explosion then the energy required to make them is still stunningly ridiculous, just not quite as stunningly ridiculous.

In order to see the GRB, the beam would need to be pointed directly at Earth.  That means that for every GRB seen there must be hundreds or thousands that are not seen because they're not pointed at us.  So not only are GRBs preposterously powerful and preposterously far away, they are also preposterously common.  Such a big bang occurring every few minutes is almost too preposterous to believe but that is exactly what the data seems to say.

GRB 080319B
Artist's concept of gamma-ray jets.
Source: NASA Swift
So what can produce that kind of energy?  There are a couple possible explanations:  long and short.  A long GRB, lasting more than two seconds, is the most commonly observed.  Long GRBs seem to be linked to young galaxies with rapid star formation and the corresponding collapse of super massive stars.  Not just super massive like a fat sun but super massive like most of our entire solar system could fit inside one of these giant balls of destruction.  When one of these super massive stars, rotating very fast, collapses all the way down to a neutron star or black hole, then funky things start to happen.  Things like large amounts of highly energetic matter being released in tight beams at 99.995% the speed of light and flung all the way across the universe.

Short GRBs are more difficult to explain.  Maybe we're only seeing the edge of the beam or maybe something totally different is happening.  Maybe it is two neutron stars slamming into each other or maybe a white dwarf star falling into a black hole.  Astronomers are still trying to figure it all out.  Some progress has been made yet the debate continues.

NASA's Swift satellites has seen more than 500 GRBs.  NASA's Fermi Gamma-Ray Space Telescope is also hot on the trail, ready to "crack the mysteries of the stupendously powerful explosions known as gamma-ray bursts."  There's no telling what they might discover next.

Close only counts in horseshoes
Global thermonuclear warfare is a gentle game of patty-cake compared to the Armageddon Death Ray that is a GRB.  Even from the far side of our galaxy, a GRB could easily extinguish life on Earth.  It has been suggested that a GRB may have been responsible for the Ordovician-Silurian extinction 440 million years ago.  There is little evidence for or against this hypothesis but a GRB would certainly do the trick.

A GRB is not visible unless pointed directly at us so in that sense we're being hit by GRBs all the time.  It's like seeing a lighthouse from way out at sea, sure it's pointed at you but you don't need to squint until you get a little closer.  GRBs are so bright that closer means anything inside our galaxy.  Luckily, most stars in our galaxy are too small to generate a hypernova type GRB event.  Most, but not all.

Eta Carinae
Eta Carinae is a massive star in our galaxy
that may explode at any time.
Source: NASA Hubble
Eta Carinae is a faint star in the southern constellation Carina.  It is about 7500 light-years from us and is expected to explode into a supernova or hypernova some time between now and maybe a million years from now.  Back in 1843 astronomers saw it explode into a supernova and it was temporarily the second brightest star in the sky.  Oddly, after astronomers finished squinting, they saw that the star was still there and hadn't completely exploded after all.  Some science was performed and the event was dubbed a supernova impostor.  Then more science was done and now astronomers watching interstellar reflections from that supernova impostor are once again scratching their heads and trying to figure out exactly what is going on.

Eta Carinae is not pointed at us so even if it generated a GRB, we would probably be safe.  There are other super massive stars though, such as WR 104, that may be pointed our way.  Of course the galaxy is a large place with a lot of stars so there are probably stars we simply have not noticed yet.  And any reasonable person will leave room for stars we thought we understood but then surprise us with their strangeness.

The universe is a very large place with a lot of very strange things going on.  Some of those things can be quite dangerous while others are downright fascinating.  Compared to the primitive Vela satellites, chances are good that the NRO has some amazing stuff in orbit.  There's no telling what crazy things might be discovered next, large or small.

Scale

Among many other references, I found the original inspiration for this story in the book
"Death from the Skies" by Phil Plait.




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