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<p class="wp-block-paragraph">As we gaze up at the cosmos from our little planet, it&#8217;s easy to feel small and insignificant amongst the immensity of space. Yet the stars and celestial events happening lightyears away can sometimes have very real and direct impacts on our lives here on Earth. Let&#8217;s explore the top 5 space events that could cause effects felt across our planet.</p>



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<li><strong>Asteroid Impacts</strong></li>
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<p class="wp-block-paragraph">Asteroids large and small are constantly zooming around our solar system. Most pass by Earth completely harmlessly. But every so often, an asteroid lines up to strike our planet in an epic collision. The last major asteroid impact happened 65 million years ago when a 6-mile-wide rock smashed into the Yucatán Peninsula, wiping out the dinosaurs.</p>



<p class="wp-block-paragraph">Another dino-killer asteroid strike today could erase human civilization. Smaller asteroids could still cause immense regional damage and tsunamis. In 2013, the 367-foot-wide Chelyabinsk meteor exploded over Russia, injuring over 1,600 people with its shockwave. Astronomers are tracking the orbits of thousands of near-Earth asteroids, giving us some warning if one heads our way. Diverting a killer asteroid’s orbit may be our planet’s only hope if we spot one late.</p>



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<li><strong>Close Calls with Comets</strong></li>
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<p class="wp-block-paragraph">Comets originate from the icy outer realms of our solar system. As they pass near the Sun, they heat up and spew gases and dust to form their glowing tails. Most comets are small and harmless as they plunge past Earth every few decades or centuries. But what if a truly gargantuan comet entered the inner solar system?</p>



<p class="wp-block-paragraph">Some scientists hypothesize that close flybys of comets could alter Earth’s orbital path or rotation. The gravitational tugging from a hefty comet could shift our planet’s angle relative to the Sun ever so slightly. Such effects would slowly compound over many comet visits to influence Earth’s climate and seasons. One dubious (and controversial) theory blames a close comet encounter 13,000 years ago for kickstarting 1,300 years of sudden cooling, known as the Younger Dryas period. While the evidence is scant, it illustrates how comets could meddle with terrestrial affairs from time to time.</p>



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<li><strong>Supernova Explosions</strong></li>
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<p class="wp-block-paragraph">Supernovae represent the cataclysmic explosions that punctuate the endings of large stars. A nearby supernova could inflict considerable harm on our biosphere. The initial blast of high-energy radiation would incinerate the ozone layer that defends us from the Sun’s ultraviolet emissions. With the ozone severely depleted for around 5 years, surface radiation dosage would soar to extremely hazardous levels. It could spark mass cancer outbreaks in humans and wildlife alike. Plants and animals accustomed to life under the protective blanket of our ozone would be hit extremely hard. A supernova closer than 32 lightyears could trigger a global extinction.</p>



<p class="wp-block-paragraph">Thankfully most supernova candidates reside farther away than that. Still, supernova radiation and its cosmic rays can interact with atoms in our upper atmosphere to produce radioactive nuclei that blanket Earth in hazardous fallout for centuries. Molecysts of ancient supernovae and their radioactive tracers have been discovered on the seafloors, suggesting such events have affected our planet across its 4.6-billion-year lifespan.</p>



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<li><strong>Gamma Ray Bursts</strong></li>
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<p class="wp-block-paragraph">Gamma ray bursts (GRBs) rank among the most highly-energetic events known. GRBs are intensely-focused eruptions of gamma rays thought to emanate from collapsing massive stars or merging neutron stars. If a GRB were to flash towards Earth from a nearby star system, consequences would be severe. The initial high-intensity gamma and X-rays from a GRB could burn up Earth’s protective ozone layer just like a supernova. However, GRB rays shine in tightly-beamed jets, so only planets directly in the line of fire would be affected.</p>



<p class="wp-block-paragraph">Thereafter, the reduced ozone would still admit hazardous ultraviolet rays for around a decade until our ozone naturally replenishes itself. Unlike wide-field supernova blasts, GRBs pose more of a pinpoint threat. Still, astronomers think there could be over one GRB per galaxy per several hundred thousand years. With billions of galaxies in our observable universe – and with GRB jets capable of traveling billions of lightyears – GRBs likely represent an underrated hazard for habitable worlds like ours floating through space.</p>



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<li><strong>Solar Superflares</strong></li>
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<p class="wp-block-paragraph">Our Sun may seem like a predictable, dependable orb as we bask in its rays each morning. Yet our steady middle-aged star still holds some chaotic surprises. NASA’s Kepler Space Telescope has witnessed distant stars suddenly brightening by superflares thousands of times more powerful than the strongest solar flares ever recorded on the Sun. Some superflares are potent enough to strip exoplanet atmospheres. If an exceptionally strong superflare erupted from our own Sun, some of that intense X-ray and UV radiation would get absorbed by Earth’s atmosphere. The extra energy could destabilize atmospheric chemistry – depleting ozone as usual while also modifying how methane interacts with other molecules.</p>



<p class="wp-block-paragraph">Moreover, energized solar particles from the superflare would infiltrate our magnetosphere to damage satellites and blackout communication infrastructure. The largest solar storm on record – the 1859 Carrington Event – caused telegraph lines to spark and shocked operators even after disconnecting the batteries. Building infrastructure that withstands super solar storms will be key as we become ever-more reliant on electronics vulnerable to such space weather. While uncommon events, solar superflares illustrate how our parent star could wreak temporary havoc if caught unexpectedly.</p>



<p class="wp-block-paragraph"><strong>Keeping Watch for Tumultuous Celestial Events</strong></p>



<p class="wp-block-paragraph">Our planet exists within a solar system hurtling through a galaxy rocketing within an expanding universe filled with mysteries we have only begun to grasp. While many celestial events occur too far away or infrequently to bother Earth, some could have serious widespread consequences if our planet happens to be caught at the wrong place at the wrong time. Only by tracking near-Earth asteroids, studying stars at various life-cycle stages, monitoring our Sun’s stormy moods, and scanning the cosmos for explosive high-energy events can we have any hope of predicting – and just maybe technologically mitigating – some of these tumultuous cosmic threats to our biosphere as Earth plows through the stellar void.</p>

The 5 Celestial Events Shaping Earth’s Future
As iau0601a but without annotations.