HONG KONG: A team of astronomers from the US, Europe, Chile and South Africa has determined that 70,000 years ago a recently discovered dim star probably passed through the solar system’s distant cloud of comets, the Oort Cloud.
Dr. Eric Mamajek from the University of Rochester led the group which closely studied the event. They tell, “The small tangential motion and proximity initially indicated that the star was most likely either moving towards a future close encounter with the solar system, or it had ‘recently’ come close to the solar system and was moving away.”
To determine the star’s trajectory the researchers looked at both its tangential velocity and radial velocity using spectrographs on large telescopes in both South Africa and Chile. Backward tracing of the measurements revealed the star’s position 70,000 years ago.
At this point in the history our planet would have been host to Neaderthals, as well as, perhaps, modern humans. Observing the star’s trajectory, they suggest that it passed roughly 52,000 astronomical units away (or about 0.8 light years, which is 8 trillion km, or 5 trillion miles). This is very close, considering the fact that Proxima Centauri, our closest neighbor star, is 4.2 light years distant. They are 98%certain that it went through the “outer Oort Cloud,” a region at the edge of the solar system that is filled with trillions of comets a mile or more across.
“There are trillions of comets in the Oort cloud and likely some of them were perturbed by this object, and some may have been perturbed onto orbits which will bring them into the inner solar system (in the distant future). But so far it seems unlikely that this star actually triggered a significant ‘comet shower,’” researchers added.
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