Scientists have spent decades debating whether asteroids and comets hit the Earth at regular intervals. At the same time, a few studies have found evidence that the large extinction events on Earth – such as the one that wiped out the dinosaurs 66m years ago – repeat themselves every 26m to 30m years. Given that there’s good evidence that an asteroid triggered the dinosaur extinction, it makes sense to ask whether showers of asteroids could be to blame for regular extinction events.
The question is extremely important – if we could prove that this is the case, then we might be able to predict and even prevent asteroids causing mass extinctions in the future. We have tried to find out the answer.
Today, there are approximately 190 impact craters from asteroids and comets on Earth. They range in size from only a few meters to more than 100km across. And they formed anywhere between a few years ago and more than two billion years ago. Only a few, like the famous “Meteor Crater” in Arizona, are visible to the untrained eye, but scientists have learned to recognize impact craters even if they are covered by lakes, the ocean or thick layers of sediment.
But have these craters formed as a result of regular asteroid collisions? And if so, why? There have been many suggestions, but most prominently, some scientists have suggested that the sun has a companion star (called “Nemesis”) on a very wide orbit, which approaches the solar system every 26m to 30m years and thereby triggers showers of comets.
Nemesis would be a red/brown dwarf star – a faint type of star – orbiting the sun at a distance of about 1.5 light-years. This is not an impossible idea since the majority of stars actually belong to systems with more than one star. However, despite searching for it for decades, astronomers have failed to observe it, and think they can now exclude its existence. Read more...
The question is extremely important – if we could prove that this is the case, then we might be able to predict and even prevent asteroids causing mass extinctions in the future. We have tried to find out the answer.
Today, there are approximately 190 impact craters from asteroids and comets on Earth. They range in size from only a few meters to more than 100km across. And they formed anywhere between a few years ago and more than two billion years ago. Only a few, like the famous “Meteor Crater” in Arizona, are visible to the untrained eye, but scientists have learned to recognize impact craters even if they are covered by lakes, the ocean or thick layers of sediment.
But have these craters formed as a result of regular asteroid collisions? And if so, why? There have been many suggestions, but most prominently, some scientists have suggested that the sun has a companion star (called “Nemesis”) on a very wide orbit, which approaches the solar system every 26m to 30m years and thereby triggers showers of comets.
Nemesis would be a red/brown dwarf star – a faint type of star – orbiting the sun at a distance of about 1.5 light-years. This is not an impossible idea since the majority of stars actually belong to systems with more than one star. However, despite searching for it for decades, astronomers have failed to observe it, and think they can now exclude its existence. Read more...