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Study Finds Alien Star Passed Through Our Solar System 70,000 Years Ago


Image credit: Michael Osadciw/University of Rochester. Artist’s impression of Scholz’s star with its brown dwarf companion in the foreground

Based on a recent study by a group of astronomers, at the time when the modern humans first started to move around Asia, a red dwarf star, with the distance of only 0.8 light years from the sun, has passed.

It was never observed by our wandering ancestors. Although it was just 20 light-years away, Scholz’s star, the nickname of this red dwarf star, had been discovered just in 2013 because of its faintness. Even if it is 25 times closer, and therefore 600 times brighter, binoculars are required to detect such star, which is officially known as WISE J072003.20-084651.2. But magnetically active stars like Scholz’s could give light and so it might be occasionally bright enough to confuse an observant early human

It was certain that Scholz’s star could have passed through the Oort cloud housing most comets, but it would be possible that it failed to get to the inner cloud where a gravitational disturbance could touch off a large deal of comets into the inner solar system.

According to the report in the Astrophysical Journal Letters, Dr. Eric Mamajek and his team from the University of Rochester regarded the event as “the closest known flyby of a star to the solar system”. It is also reported that the star HIP 85605 could get to be close with the distance of 0.13 light-years in a quarter of a million years’ time. However, Mamajek’s team have the strong evidence to refute such claim.

Scholz’s star is thought to be one of many red dwarfs appearing on the sky’s photographic images, but it is just noticed recently. Once their distances were taken measurement, some of the closer objects began to arouse attention, but with the distance of 20 light years, Scholz’s star was not that outstanding. At the same time, it was not moving very fast across the sky.

In order to identify whether the star was coming to us or leaving off, by using Doppler shiftDr. Valentin Ivanovof the European Southern Observatory had made measurement of its radial velocity. As a result, he discovered that it was moving away from the sun in a faster speed.

As Mamajek said, most stars in the close distance would demonstrate quite larger tangential motion. The small tangential motion and proximity first showed that the star was possibly moving towards a future close encounter with the solar system, or it had come close to the solar system recently and was flying away. It was sure that the measurements of radial velocity were in line with it going away from the Sun’s vicinity, so it should be a close flyby in the past. At present, the star is flying away from our planet five times as fast as the Voyager 1 spacecraft.

Calculation on the path of a star poses some uncertainty, because of distortions introduced by the gravity of other nearby objects. However, in Mamajek’s conclusion, there was a 98% chance that Scholz’s star would have passed through the Oort cloud, although it would not go through its inner region.

The Gaia satellite of European Space Agency will map out the distance and velocities of a billion stars, therefore, the cases such as Scholz’s star and HIP 85605 would be just a foretaste of what we are intended to learn more about the space.