About 70,000 years ago, a binary stellar system called ‘Scholz’s star’ passed within only 52,000 astronomical units (AU) of the Sun, i.e., within the icy Oort Cloud, a region at the edge of our Solar System filled with trillions of comets a mile or more across. The movement of some of these objects is ‘still marked by that stellar encounter,’ according to a new study published in the Monthly Notices of the Royal Astronomical Society Letters.
Scholz’s star flew through the Oort Cloud 70,000 years ago. Image credit: José A. Peñas / SINC.
Scholz’s star, also known as WISE J072003.20-084651.2, is a low-mass binary system in the southern constellation Monoceros, approximately 20 light-years away.
First discovered in 2013 by German astronomer Ralf-Dieter Scholz, the binary system consists of a red dwarf star with a mass of just 0.09 solar masses and a substellar object called a brown dwarf.
The system’s trajectory suggests that 70,000 years ago it passed roughly 52,000 AU (about 0.8 light years, which equals 5 trillion miles, or 8 trillion km) away.
“Nowadays Scholz’s star 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,” said astronomers Carlos and Raúl de la Fuente Marcos of the Complutense University of Madrid and University of Cambridge’s Dr. Sverre Aarseth.
“It is likely that our ancestors saw its faint reddish light in the nights of prehistory.”
Artist’s conception of Scholz’s star — the red dwarf primary and its brown dwarf companion (foreground) — during its flyby of the Solar System 70,000 years ago; the Sun (left, background) would have appeared as a brilliant star. Image credit: Michael Osadciw / University of Rochester.
In the new study, the team analyzed nearly 340 solar system objects with hyperbolic (very open V-shaped) orbits, and in doing so they found that the trajectory of some of these objects is influenced by the passage of Scholz’s star.
“Using numerical simulations, we calculated the radiants or positions in the sky from which all these hyperbolic objects seem to come,” Dr. Carlos de la Fuente Marcos said.
“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.”
He added: “our simulations suggest that Scholz’s star approached close than 0.6 light-years pointed out in the 2015 study as the lower limit.”
“The close fly-by 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,” the astronomers noted.
“For example, the radiant of the recently-discovered interstellar asteroid 1I/2017 U1 Oumuamua is in the constellation of Lyra, very far from Gemini, therefore it is not part of the detected over-density.”
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Carlos de la Fuente Marcos et al. 2018. Where the Solar System meets the Solar Neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies. MNRAS Letters 476 (1): L1-L5; doi: 10.1093/mnrasl/sly019
