When the Blue Ring Nebula was first spotted by NASA’s Galaxy Evolution Explorer (GALEX), teenager Keri Hoadley said goodbye to middle school, and astronomers couldn’t understand what that faint gas bubble with a star in the center was. Now astrophysics and mathematics Keri Hoadley and her team have the answer: she is the youngest known example of two stars merged into one.
According to the researchers, the nebula was formed by the recent stellar fusion between the remnants of a sun like ours and those of another star 10% of its size. Upon dying, the larger star became a supergiant, dangerously approaching its mate, attracting her.
The tiny star, when swallowed, ejected its debris in a ring around the now swollen sun. The violent event that led to the formation of the Blue Ring Nebula launched a hot cloud of debris into space, which ended up dividing into two, both cone-shaped and traveling in opposite directions.
The mystery of blue light
Let’s go back to 2004, when scientists saw the blue nebula. GALEX was designed to understand star formation through the census of populations of young stars in other galaxies, using ultraviolet light.
Most of the stars captured by GALEX radiated near ultraviolet, which appears in the images in yellow, and distant ultraviolet, represented by blue – the mysterious nebula only emitted this light. The object inside looked like the remains of a supernova or an agonizing star like the sun.
But what was inside the Blue Ring Nebula was not rubble, but a living star. And it did not emit other wavelengths of light; only blue light. Two years passed, and the GALEX team, using the telescope at the Palomar Observatory and those at the WM Keck Observatory, discovered that something violent had happened to the star, and that it was attracting a great deal of material to itself. But where?
“For a long time we thought that there was a gifting planet being torn apart by the star, sending gas out of the system,” said astrophysicist Mark Seibert, a member of the GALEX team.
Mathematics and computing
Between 2012 and 2017, the GALEX team gathered data obtained from eight telescopes, historical observations of the star since 1895 and more from citizen scientists. The nebula, however, remained unexplained.
That was when Keri Hoadley joined GALEX and took it upon himself to end the mystery. The solution would come from the application of the collected data to mathematical and computational models – the help of the theoretical astrophysicist specialist in cosmic fusion simulations Brian Metzger was unique.