NASA's Kepler captures details of unusual stellar explosion
The universe is full of mysterious exploding phenomena that go boom in the dark. NASA’s Kepler Space Telescope has caught a kind of stellar explosion called a Fast-Evolving Luminous Transient (FELT) in the act thereby helping scientists to solve the mysterious ephemeral event. Stellar explosions forge and distribute materials that make up the world in which we live, and also hold clues to how fast the universe is expanding.
Now, scientists have used US Space agencu’s Kepler to catch FELTs in the act and determine their nature. They appear to be a new kind of supernova that gets a brief turbo boost in brightness from its surroundings. “We collected an awesome light curve. We were able to constrain the mechanism and the properties of the blast,” said Armin Rest from the Space Telescope Science Institute in the US.
“We could exclude alternate theories and arrive at the dense-shell model explanation. This is a new way for massive stars to die and distribute material back into space,” said Rest. Kepler’s ability to precisely sample sudden changes in starlight has allowed astronomers to quickly arrive at this model for explaining FELTs, and rule out alternative explanations. Researchers conclude that the source of the flash is from a star after it collapses to explode as a supernova.
The big difference is that the star is cocooned inside one or more shells of gas and dust. When the tsunami of explosive energy from the blast slams into the shell, most of the kinetic energy is immediately converted to light. The burst of radiation lasts for only a few days – one-tenth the duration of a typical supernova explosion. Over the past decade several FELTs have been discovered with timescales and luminosities not easily explained by traditional supernova models. Only a few FELTs have been seen in sky surveys because they are so brief.
Unlike Kepler, which collects data on a patch of sky every 30 minutes, most other telescopes look every few days. Therefore, they often slip through undetected or with only one or two measurements, making understanding the physics of these explosions tricky. In the absence of more data, there have been a variety of theories to explain FELTs: the afterglow of a gamma-ray burst, a supernova boosted by a magnetar (neutron star with a powerful magnetic field), or a failed Type Ia supernova. Kepler’s precise, continuous measurements that allowed astronomers to record more details of the FELT event.