Scientists shocked by abundance of massive stars; Predict increase in supernova explosion, black hole

ESA/Hubble & NASA

A new study claims that heavyweight stars might be abundant in the universe than previously recorded. These supersized stars might also be the reason behind the evolution of the universe. The paper has been published in the journal Science.

Heavyweight stars are responsible for the major events occurring in the cosmos. When big stars die they explode, thus creating supernovas. Remains of these supernovas and dead stars contain the neutron stars and black holes. Past studies suggested that stars above 150 solar masses cannot form. However, the current study proves the existence of stars up to 200 to 300 solar masses.

"In the past, it has been suggested that stars above 150 solar masses cannot form," said lead author Fabian Schneider, an astrophysicist at the University of Oxford in England. But in light of the new study, "it seems likely that stars up to 200 to 300 solar masses can actually form."

Speaking of the evolution of the universe, the massive stars are the source of the "metals" present in the cosmos. According to astronomers, these metals are heavier than helium. Schneider claims that the big stars forge these metals, reports

Big stars contain more fuel than the smaller ones and hence they burn longer thus generating more heat and radiation and charged particles. Previously it was believed that this radiation led to the process of reionization which helped the universe to evolve out of the darkness.

After the Big Bang, the universe was filled with electrically charged particles or ions. After 380,000 years the ions cooled down and transformed to neutral hydrogen gas which ionized after gravity pulled matter to form the first stars. The gas has stayed in the same form since then. After the process of reionization light began travelling freely through space.

According to Schneider, massive stars are rare and this makes studying them in details difficult. The heavyweight stars live for a shorter period of time as they burn hot thus exhausting their fuel. The sun now is 4.6 million years old and is expected to continue glowing for another 5 billion years.

Schneider and his team studied the Tarantula Nebula thoroughly to assess the lives and deaths of big stars. The Tarantula Nebula is located about 180,000 light-years from Earth in the Large Magellanic Cloud galaxy. This nebula consists of some massive stars having greatest masses yet detected including R136a1, the most recent star known to have more than 10 times the mass of the sun. In order to study the 800 massive stars in Tarantula Nebula scientists used the European Southern Observatory's Very Large Telescope in Chile.

This happens to be the largest star-forming region and is also called the 30 Doradus or 30 Dor. According to scientists, it is so powerful that even if it were only 1,300 light-years away and 1,000 light-years wide, it would do the work of 60 full moons and would be enough to cast shadows on Earth.

The research revealed that 30 Dor houses more massive stars than previously thought. The current study brushes off the previously calculated number of massive stars which they believed to be around 30 or 40 solar masses or less. The team has found stars up to 200 to 300 solar masses in size.

Why suddenly a hike in the number of massive stars?

One possible explanation is that Tarantula Nebula has only 40 percent "metal" as the sun and lower metallicity usually forms a greater number of massive stars. Also, since the region is known as the starbust region as it contains an extraordinary rate of star formation, it is believed that the previous generation of stars heated up the clouds which formed the later generation of massive stars.

If massive stars are more in the universe then, according to Schneider, it can increase supernova explosions by 70 percent and black hole formation might see a 180 percent increase. They can end up providing more ionizing radiation.