- NASA's Hubble Space Telescope captured a star that exploded and died 11 billion years ago.
- A massive galaxy cluster warped light from that supernova into three reflections.
- The three imprints show different colorful stages of the supernova explosion.
NASA's Hubble Space Telescope watched a distant star die, explode, and fade away in rare detail.
The star died more than 11 billion years ago, when the universe was less than a fifth of its current age of 13.8 billion years, but the light from its violent explosion just reached Earth. This is the first time astronomers have looked closely at a supernova so early in the universe's history.
Hubble watched the star collapse, expell its outer layers in a violent explosion, and then cool. Based on the supernova's brightness and how quickly it cooled, scientists calculated that this star was 500 times larger than the sun. The researchers' paper was published in the journal Nature on Wednesday.
"You've got the massive star, the core collapses, it produces a shock, it heats up, and then you're seeing it cool over a week. I think that's probably one of the most amazing things I've ever seen," Patrick Kelly, study leader and an assistant professor in the University of Minnesota's School of Physics and Astronomy, said in the NASA press release.
That's a rare sight, especially so early in the universe, since a supernova's explosion and cooling happens over the course of just a few hours or days.
The multi-colored faces of a supernova, warped in space-time
Hubble spotted this supernova through gravitational lensing. That's what happens when a cluster of distant galaxies is so massive that it warps space-time, bending and magnifying the light from stars far in the distance behind it. That creates mirror images of those stars, reflected back at us.
In this case, the gravitational lensing created three images of the same supernova at different points in time. That's because the light from the explosion took three different paths around the massive galaxy cluster. The paths had different lengths, so the light arrived at different times, reflecting images from three different stages in the star's death.
That's why the three reflections are different colors — as the supernova's temperature changed rapidly over the course of a week, so did its color. In the early, extremely hot phases, the star appeared blue. As it cooled, it looked redder.
"It is quite rare that a supernova can be detected at a very early stage, because that stage is really short," Wenlei Chen, a postdoctoral researcher in the University of Minnesota School of Physics and Astronomy, who studied this supernova, said in the statement.
"It only lasts for hours to a few days, and it can be easily missed even for a nearby detection. In the same exposure, we are able to see a sequence of the images — like multiple faces of a supernova," Chen said.