A fateful asteroid caused the demise of the dinosaurs (other than birds) 65 million years ago. But this was not a single event. Many mass extinctions in our planet’s past were caused by meteorite impacts, and remain a clear and present danger today. In 2013, the Chelyabinsk meteor, the size of a six-story building, crashed over Russia and produced an explosion stronger than a nuclear one. Just a century ago, the Tunguska meteorite exploded over Siberia, flattening 80 million trees over an area of 2,150 square kilometers.
The largest collision event in Earth’s history occurred shortly after our planet formed, when it collided with a planetary body the size of Mars. This resulted in the formation of Earth’s moon and oceans of long-lived magma on the surface, making our planet uninhabitable for some time.
Asteroid impacts can cause a cascade of life-ending events. In the case of the extinction of the dinosaurs, the primary killing mechanism was the ejection of molecules into the atmosphere that block sunlight, preventing photosynthesis and leading to the massive death of plants. This was followed by food shortages and severe climatic fluctuations after the great impact that caused the extinction of animals that depend on plants directly or indirectly for food.
Asteroids are not the only danger from space. Supernova explosions have been linked to a minor mass extinction only 2.6 million years ago and the Late Devonian mass extinction about 350 million years ago, resulting in the loss of three-quarters of all species on our planet. Nearby supernova explosions kill by flooding Earth’s atmosphere with radiation that destroys the protective ozone layer. Fortunately, the closest star at risk of a supernova anytime soon is Betelgeuse, which is 640 light-years away. (The Late Devonian supernova was only 65 light-years away.)
An even worse catastrophe could happen if Earth got stuck in the narrow “beam” of a gamma-ray burst caused by the explosion of a massive star or the collision of two neutron stars. Gamma ray bursts produce unimaginable amounts of energy and can kill from far away. Such a catastrophe has been suggested as the cause of the Ordovician-Silurian mass extinction about 450 million years ago, which killed half of all animal life on Earth.
Wolf-Rayet stars, which are at least 20 times the mass of our Sun, are capable of emitting gamma-ray bursts. One of these stars, WR-104 in the gamma velorum system, is 800 light-years away. This seems safe enough, but it may not be, because the axis of rotation of the star is more or less directed in our direction. A gamma-ray burst could blast us at the speed of light, and there would be no warning time.
James Webb Space Telescope to the Rescue
Now, the good news. The recently launched James Webb Space Telescope (JWST) may help us identify some of these cosmic threats in advance. One of JWST’s main goals is to photograph planets around other stars, but it will also be able to observe small objects such as asteroids and comets in our solar system. Even when it was still in its commissioning period, the telescope tracked an asteroid (Tenzing 6841) — the first time a space observatory had been able to do so.
One of JWST’s early observations includes Wolf-Rayet (WR) stars and how they affect dust in the interstellar medium. This may lead to a better understanding of when these objects may be producing bursts of gamma rays.
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However, even if the JWST acts as a warning system for certain hazards in space, some disasters provide little or no warning. Given that there may be more “rogue planets” than there are star-related planets, one of these planets may cross our path one day. The same applies to a neutron star or black hole, which could cause the destruction of our entire solar system. You won’t even have to hit us directly. By destabilizing the orbits in the asteroid belt or Oort cloud, it would be https://news.google.com/https://news.google.com/https://news.google.com/https://news.google.com/news. google.com/https://news.google.com/https://news.google.com/https://news.google.com/https://news.google.com/https:/ /news. google.com/https://news.google.com/url Countless asteroids or comets are heading in our direction.
The ultimate solution to these cosmic threats, if we are to survive in the distant future, is to become a multi-planetary species. In the meantime, let’s at least keep an eye on any looming dangers. We don’t want to end up like dinosaurs.