Strange star can reveal what ancient supernovae were like

A star with a curious chemical composition has been found. Called LAMOST J1010+2358, it sits in the Milky Way’s halo and contains evidence of ancient supernovae, which occurred when the universe’s first massive stars ended their lives in explosions.

After the Big Bang, the universe remained dark for a few hundred million years, but that changed when the first stars appeared. According to numerical simulations, they were a few hundred times the mass of the Sun.

Among these stars were those with 140 to 260 solar masses. At the end of their lives, they explode in pair-instability supernovae, a different type of supernova than stars of later generations. These cosmic explosions should have left chemical traces in the atmospheres of stars from other generations.

Now, researchers led by Zhao Gang of the Chinese Academy of Sciences may have found these remains. Through spectroscopic observations with the Subaru telescope, they found that the star J1010+2358 has a low abundance of sodium and cobalt, and that the ratio of sodium to iron in it is less than 1/100 compared to the Sun.

These and other features indicate that the star was born in a gaseous cloud dominated by the remnants of such a supernova, caused by the death of a 260-solar-mass star. “Prior to this study, no evidence of supernovae from such massive stars was found in metal-poor ones,” Gang said.

For the authors, the abundance of iron in the star is much higher than that of most low-metallicity stars. This suggests that second-generation stars, born from a gas pair dominated by unstable supernovae, may be more metal-rich than previously thought.