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Rare Grains from Supernova

Extremely Rare Grains from Supernova Found in Antarctic Space Rocks

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Researchers looking closely at a pair of meteorites salvaged from the ice of Antarctica discovered something surprising and exciting. Inside of each, they found a single microscopic grain of sand that seems to have been formed in a supernova several billion years ago .

This is the first time silicate samples produced by a supernova have ever been found in a meteorite or anywhere else. Most likely, this supernova occurred before our solar system was even formed, and its remnants only arrived here after an unimaginably long trip through the void of space.

These tiny specks of silicate were invisible to the naked eye. They were discovered using a high-tech device known as a NanoSIMS50 ion microprobe, which magnified a rock sample from the meteorite by 20,000 times. Their exact chemical makeup of these specks was highly unusual; it featured traces of the isotope Oxygen-18, which can only be created inside the hellish forge of a supernova.

Interestingly, the two grains of sand were found separately. One was discovered by a graduate student named Pierre Haenecour from Washington University in St. Louis (USA). The other was detected by Xuchao Zhao of the Institute of Geology and Geophysics in Beijing, China, in a meteorite retrieved by the Chinese Antarctic Research Expedition.

Despite its remote and hostile location, Antarctica is an excellent place to search for meteorites . Its frigid, dry climate is ideal for preserving meteorite fragments in a pristine state, and the movement of the continent’s ice sheets helps to concentrate meteorites in areas where they can be found more easily. The lack of tree cover, standing lakes and running rivers also makes the landscape easier to explore, even with the severe cold that makes living in Antarctica impossible.  

Finding the silicate grains was a notable event because these particular types of supernova particles had not been uncovered before. But this is not the first time supernova leftovers have been retrieved from meteorites. Traces of rare isotopes like chromium-54, aluminum-26 and iron-60 have all been found inside meteorites, and these substances all come from the interior of massive exploding stars. 

The search for more supernova-saturated meteors will continue, in Antarctica and elsewhere. But we don’t have to look inside rocks from space to find more supernova footprints. In fact, they’re all around us all the time. They’re the very stuff from which our planet was created.

The Incredible Creative Power of Supernovas

Sometime before our solar system formed 4.6 billion years ago, a supernova exploded in our immediate interstellar neighborhood. The force of this blast was so tremendous that it actually played a role in the creation of our solar system.

The shock wave from that supernova eventually crashed into a rotating cloud of gas and dust in this sector of the Milky Way. This collision triggered a chain reaction, causing the cloud to condense. The rotation plus the collapse triggered the formation of planets, moons and other rocky bodies, and once everything cooled and settled into their solar orbits an authentic solar system had officially been born.

In addition to the shock wave, the supernova also created a widely dispersed spray cloud of various elements produced inside the star that exploded. Meteors were one effective depository for these tiny grains, and billions of years later they would shower down on Earth to leave us clues about the beginning of our solar system.

Hydrogen and helium have been by far the most plentiful elements in the universe throughout its existence. Together they comprise about 98 percent of all matter, with the other 90 or so elements found in nature making up the other two percent.

Despite these overwhelming ratios, here on Earth the heavier elements are dominant. In fact hydrogen and helium make up just one percent of our mass, which seems incredible given their ubiquity everywhere else.

The answer to this riddle is found in the stars , and in particular in those that are gigantic enough to end their lives in a supernova.

Stars convert hydrogen to helium by nuclear fusion. But eventually solar cores will run short of hydrogen and the process will stall. At this point, activity inside the star will begin to produce heavier elements, and totals will accumulate as the star slowly reaches the end of its lifespan. Large stars that burn out go through a period of expansion before contracting violently in on themselves, after which eternal pressures will become so great that the condensed star explodes in a bright, hot flash of light and energy. The heavier elements in the star’s exploding core are expelled into space at tremendous velocities and in all directions, and it is these elements that will ultimately form planets and other cool bodies.

So all the elements heavier than hydrogen and helium that make up our Earth were actually created inside stars and thrown out into space by supernova explosions.

On average, there is approximately one supernova in the Milky Way galaxy every 50 years. This is not a lot, yet without the heavier elements these explosions distribute it would not be possible for new planets and solar systems to form.

The elements that make up our planet came from at least one supernova and maybe more. It is a fascinating fact that the most destructive event the universe is capable of producing caused a cascade of developments that eventually led to the creation of a planet full of heavy elements and therefore able to support life.

Supernovas have spread the seeds of creation, here in this part of the universe and likely elsewhere as well.

Should We Be Afraid of Supernovas?

What if another supernova took place in close-by region of the Milky Way? Would it put the Earth in danger?

According to Dr. Mark Reid , an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, a supernova occurring within 30-50 light-years “would lead to major effects on the Earth, possibly mass extinctions. X-rays and more energetic gamma-rays from the supernova could destroy the ozone layer that protects us from solar ultraviolet rays. It could also ionize nitrogen and oxygen in the atmosphere, leading to the formation of large amounts of smog-like nitrous oxide in the atmosphere.”

This is a grim and frightening scenario. But thankfully its one we won’t have to worry about. There are no stars large enough to go supernova anywhere near Earth, meaning we’ll never have to face an extinction event precipitated by an exploding star.

This of course provides us with no protection against nuclear war, ecological collapse, a zombie apocalypse or a collision with a comet. But it is one less thing we have to worry about, and in these troubling times we need all the good news we can get.

By Nathan Falde

 

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