Scientists spot rare explosion of stars

After five years of observation, UCI researchers have used a new technique to find what they believe are the oldest large supernovae ever detected.

Cosmologist Jeff Cooke, the lead researcher on the project, said the discovery has the potential to help scientists understand how galaxies form and change over time because the method used to detect the stellar explosions allows them to look back to the formative years of the universe.

“When you go back in time you’re seeing a cleaner, smaller universe,” Cooke said.

The two supernovae — big stars whose lives end with an explosion after they burn up all of their fuel — are 11 billion years old (close to the estimated age of the universe, which is about 14 billion years). Previously, the oldest discovered supernovae were 6 billion years old.

In astronomy, age and distance are practically the same because light from stars travels at a set speed (a.k.a. the speed of light), so if it takes the light from a star explosion 11 billion years to get to Earth, then the star must have been 11 billion light years away when it blew up.

When things get farther, they fade, making them more difficult to find. In looking for supernovae, Cooke took a series of images of the same patch of sky from the Canada-France-Hawaii Telescope — not far from the Keck Telescope in Hawaii, which he used to find a far-away cluster of galaxies last year — and layered them on top of each other.

By juxtaposing so many images he was able to see weak lights more clearly and separate them from incidental noise and errors.

Although he is not a supernovae specialist, UC Santa Cruz cosmologist Joel Primack said that studying supernovae is important because they create all of the “heavy elements” that make up planets like Earth and our bodies. Primack and colleagues in Santa Cruz heard Cooke speak recently, when he presented his research there.

“These are the rarest things in the universe, these heavy elements. We take them for granted because we see them all around us,” Primack said.

By watching supernovae unfold, researchers get a glimpse into how such rare elements like silicon, oxygen and carbon come together to make rocky planets like Earth possible.

One big boon to Cooke in his research was the fact that even after a star explodes it leaves behind a sort of shell of glowing matter. This is important because the supernovae the cosmologist is analyzing were detected between 2003 and 2008.

When he identifies them today, the residues left in the sky that are still visible help him convince other researchers what they saw were actually supernovae and not some misleading substitutes.

“When I first did this I said surely it’s been done. It’s too obvious,” Cooke said.

Present and future research could help satiate people’s hunger for knowledge of the origins of the universe.