STScI: Hubble Captures 3 Faces of Evolving Supernova in Early Universe

This is a five-panel graphic with a large panel on the left and four smaller panels on the right.
Context Image
The first and largest panel of this 5-panel graphic appears on the left side of the screen. It is double the size of the other four panels. At the bottom left corner is the label “Galaxy Cluster Abell 370.” The image is a field of many dozens of white, yellow, red, and blue galaxies of various sizes and shapes. Some of the galaxies appear as streaks or arcs. A box in the top, left corner of this image highlights the portion of the galaxy cluster where the supernova was multiply imaged. To its left are four smaller panels, stacked two by two on top of each other. Each of the four panels is a version of the field contained in the small box within the first, large panel to the left.
Panel A
Panel A, the top left of the four smaller panels, has a label on its top left that reads “A: Combined Image (2011 to 2016).” On the next line is “F814W,” which describes the filter used to produce this image. Panel A shows a large, fuzzy, circular galaxy in the center with many smaller galaxies surrounding it. Three of the galaxies are circled and numbered, left to right: 3, 1, and 2. These are multiple images of the same galaxy. On the bottom right is the label “Lensed Galaxy.”
Panel B
To the right of Panel A is Panel B. The label on the top left of this panel reads “B: Supernova Detection (December 2010).” On the next line is “F814W,” which describes the filter used to produce this image. The image in Panel B is very similar to that of Panel A, except that on the side of each of the three circled galaxies is a bright dot. On the bottom right is the label “Lensed Galaxy and Supernova.”
Panel C
Beneath Panel A is Panel C. The label on the top left of this panel reads “C: Difference Image. On the next line is the label, “Image B minus Image A.” In this image, the large, fuzzy, circular galaxy in the center is removed, as are the other galaxies, including the three multiply imaged galaxies containing the supernova. Three small, white dots are circled and numbered, left to right: 3, 1, and 2. These are the multiple images of the supernova. On the bottom right is the label “Supernova.”
Panel D
Panel D is beneath Panel B and to the right of Panel C. The label on the top left of this panel reads “D: Color Difference Image.” On the next line is the label “F814W+F110W+F160W.” This information describes the filters used to produce this image. The characters F814W appear in blue, the characters F110W appear in green, and the characters F160W appear in red. These describe the filters used to produce this image. At the center of the image is a blue, red, yellow, and green blob, which is the central galaxy shown in different filters. Panel D shows an image subtraction process similar to the subtraction process for Panel C, but uses multiple filters of data. Three, smaller, differently colored blobs are circled and labeled. The left circle contains a reddish orange blob labeled “3 (day 8).” The middle blob is blue and labeled “1 (day 0). The right blob is turquoise and labeled “2 (day 0).” These show the different colors of the cooling supernova at three different stages in its evolution. At the bottom right is the label “Supernova.” — Through a phenomenon called gravitational lensing, three different moments in a far-off supernova explosion were captured in a single snapshot by NASA’s Hubble Space Telescope. The light from the supernova, which was located behind the galaxy cluster Abell 370, was multiply lensed by the cluster’s immense gravity. This light took three different paths through the cosmic lens of the massive cluster. The three paths were three different lengths and affected to different degrees by the slowing of time and curvature of space due to the cluster, so when the light arrived at Hubble (on the same day in December 2010), the supernova appeared at three different stages of evolution. The left panel shows the portion of Abell 370 where the multiple images of the supernova appeared. Panel A, a composite of Hubble observations from 2011 to 2016, shows the locations of the multiply imaged host galaxy after the supernova faded. Panel B, a Hubble picture from December 2010, shows the three images of the host galaxy and the supernova at different phases in its evolution. Panel C, which subtracts the image in Panel B from that in Panel A, shows three different faces of the evolving supernova. Using a similar image subtraction process for multiple filters of data, Panel D shows the different colors of the cooling supernova at three different stages in its evolution. Credit: NASA, ESA, STScI, Wenlei Chen (UMN), Patrick Kelly (UMN), Hubble Frontier Fields

Three different moments in a far-off supernova explosion were captured in a single snapshot by NASA’s Hubble Space Telescope. The star exploded more than 11 billion years ago, when the universe was less than a fifth of its current age of 13.8 billion years.

This is the first detailed look at a supernova so early in the universe’s history. The research could help scientists learn more about the formation of stars and galaxies in the early universe. The supernova images are also special because they show the early stages of a stellar explosion.

“It is quite rare that a supernova can be detected at a very early stage, because that stage is really short,” explained Wenlei Chen, first author of the paper and a postdoctoral researcher in the University of Minnesota School of Physics and Astronomy. “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.”

This was possible through a phenomenon called gravitational lensing, which was first predicted in Einstein’s theory of general relativity. In this case, the immense gravity of the galaxy cluster Abell 370 acted as a cosmic lens, bending and magnifying the light from the more distant supernova located behind the cluster.

The warping also produced multiple images of the explosion over different time periods that all arrived at Earth at the same time and were caught in one Hubble image. That was possible only because the magnified images took different routes through the cluster due both to differences in the length of the pathways the supernova light followed, and to the slowing of time and curvature of space due to gravity.

The Hubble exposure also captured the fading supernova’s rapid change of color, which indicates temperature change. The bluer the color means the hotter the supernova is. The earliest phase captured appears blue. As the supernova cooled its light turned redder.

“You see different colors in the three different images,” said Patrick Kelly, study leader and an assistant professor in the University of Minnesota’s School of Physics and Astronomy. “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!”

This is also the first time astronomers were able to measure the size of a dying star in the early universe. This was based on the supernova’s brightness and rate of cooling, both of which depend on the size of the progenitor star. Hubble observations show that the red supergiant whose supernova explosion the researchers discovered was about 500 times larger than the Sun.