In the dense galaxy cluster Abell 2744, where gravity bends light like a lens, the James Webb Space Telescope spotted a new point of light. It appeared in images from 2023 and then began to change brightness. It was a supernova, the explosion of a dying star, but not just any kind: a Type IIP. These flashes linger in the sky for a long time because the star sheds a huge shell of gas before dying, and the shock wave lights it up from within.
The flash was named PLATE-23a. It erupted in a barred spiral galaxy similar to our own, but seven times farther away: its light took about seven billion years to reach us. The telescope tracked it for three years, capturing it in twelve different colors. This let scientists see the star first brighten, then slowly dim. Its surface temperature dropped from eight thousand degrees to six thousand in just two months, like a scorching furnace cooling to the glow of embers.
By the end of the first year after the blast, the glow stopped cooling and began to fade differently — a sign that the energy was no longer coming from hot gas but from the decay of radioactive elements ejected in the explosion. This is the first result from the PLATE project, which uses the cluster's cosmic lens to peer at distant flashes. If enough such events are found, we'll learn how stars died in the young universe.
The Abell 2744 cluster warps space so strongly that the same distant galaxy can appear multiple times, like reflections in a funhouse mirror.
In the novel 'Light of Distant Stars,' a lensed supernova helps the characters peer into the universe's past — here, it actually works.