Thesunmay have a companion star that periodically bombardsEarth with storms ofcomets and asteroids, scientists fromLund University and the Swiss Federal Institute of Technology said Thursday.

New studies of Earths impact craters found asteroids tended to hit roughly every 26 million years, adding to evidence that mass extinction events could be driven by a dim companion star to our sun named after the Greek goddess of revenge, Nemesis. Under this theory, the next apocalyptic asteroid will hit Earth in 10 million years.

How likely is Nemesis to actually exist? The evidence seems to have gone back and forth in recent years, Lindley N. Johnson, NASAs Planetary defense officer who helps devise plans for the U.S. government to stop an asteroid or comet, told The Daily Caller News Foundation.

Nemesis theoretically has an extremely elliptical orbit,swinging by our sunonce every 26 million years and redirecting the orbits of asteroids and comets to bombard Earth. Researchers have never found Nemesis, but such a star would be exceedingly difficult to detect.

Nemesis would be a faint redor brown dwarf star,orbiting our sun at a distance of about 1.5 light years.The majority of stars in our galaxy actually belong to systems with more than one star.

We see dwarf stars but it is difficult to get the 3-D orbital data for such a star in our galaxy as humans do not have the time base to predict such long-scale interactions even with great observational data and that certainly does not exist for any but the closest stars, Dr. Joseph A. Nuth, a senior asteroid scientist at NASAs Goddard Space Flight Center, toldTheDCNF.

Nemesis gravity could alter the orbits of swarms of comets or asteroids in the outer solar system, placing them on a collision course with Earth.

Stellar interactions should effect Oort cloud comets, not asteroids except as secondary products of a comet storm hitting the inner solar system, Nuth said. Basically you need a massive gravitational perturbation or lots of collides to get this.

We probably cant handle a single asteroid on 5 10 years warning, Nuth said. A comet or asteroid storm coming with less than a decade warning would require dropping everything else and going to full defense as a planet and it still probably would not be enough.

The best way to stop an asteroid or comet from hitting the Earth may be to send a spacecraft up to intercept it. NASA, however, would need at least five years to construct a reliable spacecraft and man it. If more than one asteroid or comet were coming at Earth, stopping them all in time could be impossible.

Impact of an asteroids as large as 1 kilometer in size are estimated to cause global effects, i.e. enough dust, debris and/or water vapor expelled into Earths atmosphere to block sunlight and negatively affect the climate world-wide, Johnson said. An event that caused mass extinction would need to be significantly larger than that.

In 2016, NASA and other federal agencies simulated a response to an asteroid striking Earth. Officials were unable to deflect an asteroid on course to hit Earth with four years of warning. An asteroid or comet wouldnt need to be that large to potentially wipe out humanity.

The event 65 million years ago, the mass extinction of dinosaurs, is thought to have been caused by a 10 kilometer (6 mile) sized asteroid, Johnson said. Our population models indicate we have already discovered all asteroids of this size currently within the inner Solar System, i.e. within the orbit of Mars.

The amount of damage an asteroid or comet impact could do is linked not just to the size of the object, but also to the geology of the area where it strikes.

For years, paleontologists hypothesized that the size of a mass extinction might be correlated with the size of the bolide itself, Dr. Rowan Lockwood, a William & Mary paleontologist who studies extinction, told TheDCNF. In recent years, paleontologists have realized that the geology at the impact size (i.e., whether its oceanic or continental crust, limestone or sandstone) is probably more important than the size of the bolide. This might explain (for example) why the K/Pg impact [CretaceousPaleogene, which killed the dinosaurs] was so devastating and the the Chesapeake Bay Impact wasnt, despite the large size of the latter.

Asteroids big enough to cause a mass extinction should be roughly 0.6 miles in diameter. NASA outright admits theres not much the agency could do to stop such an asteroid on a collision course with Earth withoutadvanced warning.

See the Torino Scale or the Purdue Simulator but it will generally depend on both size, density and mass, especially in the case of a comet, Nuth said. A dense fast comet many tens of kilometers in radius could certainly do it.

Former NASA administrator Charles Bolden told reporters in 2013 that the only response to a large surprise asteroid on a collision coursewith Earth is to pray.

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Scientists Have Predicted When Earth Will Be Hit By An Extinction-Level Asteroid - The Daily Caller