Did Scholz’s star invade the Oort Cloud?

Scholz´s star – named for its discoverer – is now 20 light-years away. But astronomers say they’ve verified a flyby of this star 70,000 years ago that disturbed comets in the Oort Cloud.

Artist’s concept of a the red dwarf star known as Scholz’s star, a binary system formed by a small red dwarf, with about 9% of the mass of our sun, around which a much less bright and smaller brown dwarf orbits. According to astronomers, our ancestors saw the faint reddish light of this passing star system in the nights of prehistory. Image via Eric.

Astronomers announced new evidence on March 20, 2018, that the passage of Scholz´s star 70,000 years ago gravitationally disturbed our solar system’s comets and asteroids. The evidence still exists, these researchers say, in the movements of some of these objects marked by that stellar encounter. Their study will appear in the May 1, 2018, issue of the peer-reviewed journal Monthly Notices of the Royal Astronomical Society.

Astronomers have wondered about Scholz’s star at least since 2015, when a team of astronomers led by Eric Mamajek gave details of a possible stellar flyby, the closest documented so far, in a study in The Astrophysical Journal Letters.

The new study comes from the Complutense University of Madrid, from Carlos de la Fuente Marcos and Raúl de la Fuente Marcos (who are brothers), together with the researcher Sverre J. Aarseth of the University of Cambridge in the U.K. The researchers’ statement explained:

At a time when modern humans were beginning to leave Africa and the Neanderthals were living on our planet, Scholz’s star – named after the German astronomer who discovered it – approached less than a light-year from the sun. Nowadays it is almost 20 light-years away, but 70,000 years ago it entered the Oort Cloud, a reservoir of trans-Neptunian objects located at the confines of the solar system.

The de la Fuente Marcos brothers and Aarseth analyzed the nearly 340 objects of our solar system with hyperbolic orbits. Those are orbits that are very open and V-shaped.

Examples of orbital trajectories. The hyperbolic orbit – shown in blue – is found in particular for some comets in our solar system.

In this way, these researchers determined that the trajectory of some of our solar system’s smaller bodies must have been influenced by the passage of Scholz´s star. Carlos de la Fuente Marcos said:

Using numerical simulations, we have calculated the radiants or positions in the sky from which all these hyperbolic objects seem to come.

In principle, one would expect those positions to be evenly distributed in the sky, particularly if these objects come from the Oort Cloud; however, what we find is very different: a statistically significant accumulation of radiants. The pronounced over-density appears projected in the direction of the constellation of Gemini, which fits the close encounter with Scholz´s star.

The moment in which this star passed close to us and its position during prehistory coincide with the data of the new investigation and in those of Mamajek and his team, according to these scientists. De la Fuente Marcos said:

It could be a coincidence, but it is unlikely that both location and time are compatible.

He said the team’s simulations suggest that Scholz´s star approached even more closely than the 0.6 light-years pointed out in the 2015 study as the lower limit. The Oort Cloud, by some estimates, extends out at least that far and possibly much farther, perhaps even farther than halfway to, say, the distance of the next-nearest star, the Alpha Centauri system, about four light-years away.

The researchers say the close flyby of Scholz’s star 70,000 years ago did not disturb all the hyperbolic objects of the solar system, only those that were closest to it at that time. De la Fuente Marcos explained:

For example, the radiant of the famous interstellar asteroid `Oumuamua is in the constellation of Lyra (the Harp), very far from Gemini, therefore it is not part of the detected over-density.

The team expressed confidence that new studies and observations will confirm their work.

Scholz’s star may have come within a light-year of Earth, appearing in our skies at a time when modern humans were beginning to leave Africa and the Neanderthals were living on our planet. Image via José A. Peñas/SINC.

Bottom line: Scholz´s star is now 20 light-years away. But a study of the orbits of asteroids and Oort Cloud comets verifies a close flyby of this star 70,000 years ago.

Source: Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies

Source: The Closest Known Flyby of a Star to the Solar System (2015)

Via SINC/AlphaGalileo

Deborah Byrd

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