For several hundred million years after the Big Bang, the Universe was bathed with darkness. Suddenly, something excited the hydrogen and the first stars burst into light.
Scientists believe that the first generation of stars in the Universe were immense but short-lived fireballs. Eventually, they exploded into supernovae.
Astrophysicists from MIT revealed that the very first stars exploded in an asymmetrical fashion, creating powerful jets that ejected heavy elements into neighboring galaxies and paved the way to the formation of the next generation of stars.
In the study published in the Astrophysical Journal, the team presented the first observational evidence of asymmetric supernovae that took place in the early universe.
A Nearby Ancient Star Provides Clues About Early Universe
For the study, the researchers looked at one of the surviving second generation of stars in the Universe. HE 1327-2326 was discovered in 2005 by Anna Frabel, an associate professor of physics at MIT.
At the time of discovery, the star was the most metal-poor ever observed. This indicated that it was formed back when the heavy elements were yet to be created.
"The smaller stars that formed as the second generation are still available today, and they preserve the early material left behind by these first stars," said Frebel. "Our star has just a sprinkle of elements heavier than hydrogen and helium, so we know it must have formed as part of the second generation of stars."
In May 2016, Frebel and team observed HE 1327-2326 using the Hubble Space Telescope. They recorded its starlight over multiple orbits and measured the minute abundances of its elements. They discovered that the star, which orbits close to Earth 5,000 light-years away, is rich in zinc.
Powerful Explosions In The Early Universe
They collaborated with colleagues from Japan who developed simulations of first supernovae and the second generations of stars that formed after. They pored through over 10,000 simulations and found that while spherical supernovae can produce the second generation of stars that had the same composition as HE 1327-2326, none of them had the zinc signal.
The simulation that created the same conditions as HE 1327-2326 involved aspherical supernova that spewed powerful jets. They said that the explosion has a power equivalent to about a nonillion times that of a hydrogen bomb.
"We found this supernova was much more energetic than people have thought before, about five to 10 times more," explained Rana Ezzeddine, lead author of the study and a postdoctoral student at MIT. "In fact, the previous idea of the existence of a dimmer supernova to explain the second generation stars may soon be retired."
They believe that the findings might also change the current understanding of reionization, the pivotal point in the history of the universe in which gas went from neutral to ionized. Frebel proposed that the explosion of the first stars contributed to the reionization of the universe that led to the formation of the galaxies.