While time-travel, as shown in fiction, isn’t a reality, looking back in time to discover the secrets of the universe can be done.
Astronomers at NASA are doing a similar thing. According to the space agency, they “winding back the clock” to discover how and when a star blasted. The star in question exploded in the Small Magellanic Cloud a very long time ago. As you can guess, a stellar detonation is much like a bomb explosion. It leaves behind a trace like an expanding, gaseous corpse, a supernova. The remnant has been named 1E 0102.2-7219.
Now, they are retracing the speedy shrapnel from the blast to calculate using NASA's Hubble Space Telescope. The results have been promising. They have measured the velocities of around 45 tadpole-shaped, oxygen-rich clumps that were ejected by the supernova blast.
Ionized oxygen can be traced very well because it shines the brightest in visible light.
Around 22 fastest moving ejecta clumps, or knots, were picked to calculate the blast age accurately. They picked these particular knots because they think they would have been least impacted or slowed down by passage through interstellar material.
Imagine watching blast video in reverse. First, there will be debris, gradually it will start to contract. Then a point will come where everything is clear and the bomb is just being ignited. They used archival images from the telescope to attempt a similar “time-travel.” They traced the clumps’ motion backwards until all the ejecta or ejected material condensed to the one identifiable explosion site.
From there, they traced the speed at which these knots would have travelled from the explosion site to their current position in space.
Distance and time in space can be calculated with the help of light. Their estimates suggest the light from this particular blast arrived at Earth during the decline of the Roman Empire which was 1,700 years ago. Clearly, there no known records of any human civilization suggesting they witnessed a supernova blast in the skies.
Hubble has a few Advanced Camera for Surveys (ACS). Sharp and clear images from the ACS were used to track the ejecta from this supernova. Earlier, researchers had suggested calculating an average speed of all ejecta to determine their age. But the ACS revealed not all ejecta travel at the same speed. Some have been slowed down as they slammed into denser materials surrounding the supernova pre-explosion. Such knots were evicted from the study.
A neutron star, which is the crushed core of a blasted star, was observed for speed. Their best estimate is that it must have been travelling at more than 2 million miles per hour to have arrived at its current position from the centre of the explosion.
However, the particular core is only a suspected neutron and cannot be confirmed as one.
If you’re wondering how old the supernova is, you will have to wait. NASA reports the findings will be revealed at the American Astronomical Society's winter meeting.