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I did not get the second part. Nostradamus predicted 40 years of catastrophes starting with the Solar eclipse in 1999. After these 40 years the golden age will come. How does the Barnard star fit in his prophesy?
One needs to know and study Esoteric Astrology in order to understand the prophecies of Nostradamus.
Nostradamus connects the year 1999 with the equinox of autumn that occurs always in the month of September or (Seventh month). The transition of the dark forces into the light forces is celebrated on October the 31st (the evening before all hallows) and it is exactly 40 days after the 21st of September. Therefore, by applying the law of analogies it is stated that from the eclipse of September 1999 until the year 2040 there will be 40 years. This coincides with the Katun 13 of the Mayans that starts in the year 2040. Katun 13 is the beginning of destruction according with the Mayans' astrology.
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he Barnard planet is a star. It is a red dwarf, relatively cool compared to the Sun and very dim. You are right that it is aproaching the Sun (I checked online and they estimate speed of 87 miles per second). But it cannot reach the Solar system that fast as Nostradamus claimed. The star will reach a minimum distance of less then 4 light years in about 8,000 years so this is a long long time.
So... I completely disagree with you that the Barnard star will cause the global catastrophe.
The terrifying disturbance of the orbit and motion of our planet Earth is scientifically justified by the great seer, Nostradamus, through the approach of another star that for seven days will appear to be like another sun.
XLI.
"The great star will burn for seven days,
The cloud will cause two suns to appear:
The big mastiff will howl all night
When the great pontiff will change country"
St. John’s Revelation: 8: 10-11 cites the above star, calling it “wormwood” (bitterness).
"And the third angel sounded, and there fell a great star from heaven, burning as it were a lamp, and it fell upon the third part of the rivers, and upon the fountains of waters;
And the name of the star is called Wormwood:"
Moreover, Nostradamus, in a famous letter addressed to Henry II, says:
“When the sun will be totally eclipsed, a new, colossal celestial body will be seen in the sky right in the day (by the astronomers), but the astrologers (he alludes to the “famous” present and future astronomers) will interpret the effects of this body, in another manner” (in a very modern way). As a result of this wrong interpretation, no one will gather supplies for the coming penuries (referring to the great catastrophe).
Nostradamus, physician, astrologer and illuminated clairvoyant, adds, to his predictions, the matter of the revolution of the axis of the earth, but he does not indicate an exact or proper date when this will happen. He links it, nevertheless, to the double eclipse that took place in the year 1999.
And oh yes! you are not the only one who desagree with this prediction, all of the present scientists of astronomy are in agreement with you.
But I am with Nostradamus and the Mayans because they are clairvoyant sages and they could see beyond the limitations of our present astrologers.
(Hercolubus or the Barnard Star belongs to the Solar System Tylar that also travels around in the Milky Way.)

(Both Solar Systems encounter each other in the outer space every sideral year, every 26000 years of the earth.)

Barnard's Star and its System is moving towards earth and the Earth and its System is also moving towards Barnard. Do you now understand the situation?