Astronomers recently uncovered an exciting piece of our cosmic history. About 4.4 million years ago, our sun had a close encounter with two massive stars. A “scar” in the nearby clouds of gas and dust gave away this monumental event.
These clouds stretch about 30 light-years from the sun, which is zooming through space at a speed of 58,000 miles per hour. Tracking the movements of the sun, these stars, and the clouds is a complex puzzle, as everything is in constant motion.
Michael Shull, an astronomer from the University of Colorado Boulder, described it as a “jigsaw puzzle,” with all the pieces moving in different directions. The stars involved are now located around 400 light-years away in the constellation Canis Major, also known as the Great Dog.
Situated alongside these clouds is a vast region in our galaxy called the “local hot bubble,” which lacks much gas and dust. This could be crucial for understanding what made Earth a suitable home for life. Shull pointed out that the sun resides within these clouds, which help shield us from harmful radiation.
The two stars, Epsilon Canis Majoris (Adhara) and Beta Canis Majoris (Mirzam), likely passed close enough to shine brightly in our skies—up to six times brighter than Sirius, currently the brightest star visible from Earth. They are about 13 times more massive than our sun and extremely hot, reaching temperatures of up to 45,000 degrees Fahrenheit.
When these stars approached, their intense ultraviolet radiation affected the nearby clouds, ionizing the hydrogen and helium atoms within them. This process stripped electrons from the atoms and left a detectable “scar.”
Previously, astronomers noticed unusually high levels of ionization in these clouds—20% of hydrogen and 40% of helium. This sparked questions about the cause, and the new research provides answers.
Interestingly, Shull and his team noted that other sources of ultraviolet radiation, including several white dwarf stars and supernova remnants, could have also contributed to the ionization. The explosive deaths of nearby stars likely created the local hot bubble, heating the area and influencing the clouds.
However, this ionization won’t last forever. Over millions of years, the atoms will regain electrons and return to neutral states. Similarly, the massive stars themselves are on borrowed time and may go supernova in a few million years.
While their explosions pose no risk to Earth, they would certainly create a stunning spectacle. Shull remarked that the bright light from a nearby supernova would illuminate the sky beautifully but safely.
This research can deepen our understanding of how such celestial events have shaped our solar system. The findings were published in The Astrophysical Journal. For more insights into this groundbreaking study, you can check out the full article here.
