The Hubble Space Telescope has captured light from a supernova blast—an exploding star—that would have been seen from Earth 1,700 years ago.
Although there are no known records of anyone seeing it, a cosmic explosion that’s been compared to fireworks would have been visible to people in Earth’s southern hemisphere.
It’s now visible to the Hubble Space telescope as a delicate greenish-blue shell—a supernova remnant (SNR)—in a nearby galaxy to the Milky Way called the Small Magellanic Cloud (SMC).
The SNR is called 1E0102.2-7219, or E0102 for short. Here’s everything you need to know about how Hubble’s spectacular images have been used to precisely date an incredible supernova explosion.
What and where is E0102?
E0102 is the leftovers of a massive explosion of a star in a nearby dwarf galaxy—the SMC.
The images from Hubble show the aftermath of a supernova—the dissipating energy has created a spectacular display of greenish-blue filaments.
The above image of part of the SMC shows that E0102 is “close”—about 50 light-years—from a massive star-forming region of glowing hydrogen emission called N 76 and Henize. You can see that as the pink-ish section in the upper-right of the image. E0102 is at the center of the image.
What do we know about the star?
Not much, though it may have been a Wolf-Rayet star—a very large and old star made from heavy elements that had probably blown-off its hydrogen before the explosion.
Astronomers think that because the colors of E0102 indicate that it was rich in oxygen rather than hydrogen and helium.
How did astronomers use Hubble’s images?
Although E0102 was previously known about, its age was unknown. Treating E0102 as forensic evidence, astronomers used Hubble’s observations of E0102 taken a decade apart to calculate the cloud’s expansion rate.
They did that by calculating how fast 22 separate oxygen-rich knots of debris in the SNR had moved in 10 years. They then traced it back to the point in space where the progenitor star must have exploded.
Why Hubble’s longevity was so crucial
“A prior study compared images taken years apart with two different cameras on Hubble, the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys (ACS),” said Danny Milisavljevic of Purdue University in West Lafayette, Indiana, one of the leaders of the research team whose paper was presented yesterday at the 237th meeting of the American Astronomical Society.
“But our study compares data taken with the same camera, the ACS, making the comparison much more robust; the knots were much easier to track using the same instrument,” he said.
“It’s a testament to the longevity of Hubble that we could do such a clean comparison of images taken 10 years apart.”
What is the SMC?
The Small Magellanic Cloud is a satellite galaxy of our Milky Way. It’s about 200,000 light-years away in the constellation Tucana. It’s really easy to see in the night skies in the southern hemisphere.
Wishing you clear skies and wide eyes.