Astronomers have used the Hubble Space Telescope to turn back time and determine a more accurate estimate of a supernova explosion’s location and time. The star in question exploded a long time ago in the Small Magellanic Cloud, which is a satellite galaxy to the Milky Way. The exploded star left behind an expanding gaseous cloud.
The supernova remains are officially called 1E 0102.2-7219 and was first discovered by the NASA Einstein Observatory using x-rays. Researchers searched through archival images taken by Hubble and analyzed visible-light observations that were made a decade apart. Researchers measured the velocities of 45 tadpole-shaped, oxygen-rich clumps of material ejected by the supernova blast.
The scientists say that ionized oxygen is a particularly good tracer because it glows the brightest in visible light. To calculate the age of the supernova, astronomers use the 22 fastest moving ejected clumps or knots. Scientists determined the targets were the least likely to have been slowed by the passage through any interstellar material.
Once that determination was made, they traced the motion of the knots backward until the ejecta converged on a single point, which identified the explosion site. Once the supernova explosion site was known, the team was able to calculate how long it took the knots to travel from the explosion center to their current location.
Additional calculations allowed them to determine light from the blast arrived on Earth 1700 years ago during the Roman Empire’s decline. The light from the supernova would’ve been invisible to all but those living in the southern hemisphere of the Earth. The scientists point out there is no known record of the supernova explosion when it was first seen from Earth.