A low-mass red dwarf star passed through the outer Oort Cloud 70,000 years back in the closest approach made by any star into our system, discovers a team of researchers from various countries.
Lying in the constellation Monoceros and known as Scholtz’s star, it is a part of a binary system and has 8% the mass of the sun. Its companion, a brown dwarf, is said to have 6%.
The lowest end of the stellar spectrum, brown dwarfs are larger than gas giants but not as much so as to sustain hydrogen fusion for a larger period of time.
Due to its faint appearance, Scholtz’s star was discovered only a year ago by astronomer Ralf Dieter-Scholz in Potsdam, Germany, through the use of NASA’s WISE (Wide Field Infrared Survey Explorer), which mapped the entire sky in infrared during the years 2010 and 2011.
At the same time, the radial velocity of the star depicted that it was moving away from the solar system much faster than expected.
These motions led the researchers to conclude that either the star is headed toward our system, or moving away from it.
After analyzing the data, Mamajek concluded, “…The radial velocity measurements were consistent with it running away from the Sun’s vicinity–and we realized it must have had a close flyby in the past.”
Through the use of computer models, it was seen that the star passed about 5 trillion miles from our solar system around 70,000 years ago.
Mamajek and his team are 98 percent certain Scholtz’s star traveled through the outer Oort Cloud.
Although Scholtz’s star is 10th magnitude, too dim to be seen with the naked eye, it is magnetically active, which can cause it to flare at times and become significantly brighter. If this happened during its close approach to our solar system, prehistoric humans might have actually seen it.
The researchers published their findings in Astrophysical Journal Letters.