When stars of a certain mass run out of fuel, they end their lives in spectacular fashion. The outer layers, no longer pushed out by energy production in the stellar core, collapse under gravity, accelerate, and eventually compress everything beneath them into a state where matter turns into energy. This energy is released in such a way that it creates an incredible explosion, known as a supernova.
It is not easy to catch stars going supernova in the act, but astronomers have gotten pretty good at recognizing their leftovers. These are called supernova remnants and researchers can learn a lot from them. One particular supernova remnant, known as SNR 1E 0102.2-7219, has been observed in detail by Hubble, and astronomers were able to do something quite ingenious with this data. They studied its evolution backward to work out exactly when the supernova took place.
Supernova remnants are made of large ribbons of gas moving at incredible speed. As revealed in their paper that will be published in The Astrophysical Journal, for 1E 0102.2-7219, the average speed for the gaseous ejection was 3.2 million kilometers per hour (2 million miles per hour). You could go around the world in 45 seconds at that speed.
Previous estimates suggested that the light of the supernova reached Earth between 1,000 and 2,000 years ago. The team believes that their estimate is more robust, placing it at 1,700 years ago.
This time-lapse video shows the movement of a supernova remnant—the gaseous remains of an exploded star—that erupted approximately 1,700 years ago. Credit: NASA, ESA, A. Pagan (STScI), J. Banovetz and D. Milisavljevic (Purdue University)
The study also suggests some intriguing happenings in the immediate aftermath of the explosion. The team believes that the asymmetric shape of the remnant is due to the collision between the supernova blast wave and some material present only around a certain part of the system. Possibly this material was released by the star itself before it went kaboom.
The Hubble data also provides another important measurement on the system. A supernova leaves a compact object like a neutron star or black hole. Researchers believe that this particular explosion created a neutron star and the explosion was powerful enough to ricochet this object out from the center of the explosion, estimated to be moving at 830 kilometers per second (1.9 million mph).
