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Kepler solves the mystery of fast and furious explosions

This illustration shows a proposed model for a mysterious astronomical event called FELT (Fast-Evolving Luminous Transient). In the left panel, an aging red giant star loses mass due to a stellar wind. This ballts into a huge gas envelope around the star. In the center, the core of the massive star implodes to trigger a supernova explosion. In the right field, the supernova shock wave plows into the outer shell and converts the kinetic energy of the explosion into a brilliant flash of light. The radiation flash lasts only a few days – one tenth of the duration of a typical supernova explosion. Credit: NASA, ESA and A. Feild (STScI)

The universe is full of mysterious exploding phenomena that are booming in the dark. One particular type of ephemeral event known as FELT (Fast-Evolving Luminous Transient) has confused astronomers for a decade because of its short duration.

Now NASA's Kepler Space Telescope – designed to hunt planets in our galaxy – has also been used to catch FELTs in the act and determine their nature. They seem to be a new kind of supernova that gets a short burst of turbo in brightness from their environment.

Kepler's ability to accurately detect sudden changes in starlight has enabled astronomers to quickly find this model to explain FELTs and to exclude alternatives

The researchers conclude that the source of lightning stems from a star after this collapsed to explode as a supernova. The big difference is that the star is shrouded in one or more shells of gas and dust. When the tsunami of explosive energy from the explosion falls into the shell, most of the kinetic energy is immediately converted into light. The radiation outbreak lasts only a few days – one tenth of the duration of a typical supernova explosion.

Over the past decade, several FELTs with time scales and brightnesses have been discovered that are not easily explainable with conventional supernova models. And only a few FELTs have been seen in heavenly surveys because they are so short. Unlike Kepler, which collects data about a celestial area every 30 minutes, most other telescopes look every few days. Therefore, they often slip undetected or with only one or two measurements, which makes it difficult to understand the physics of these explosions.

In the absence of further data, there were a number of theories to explain FELTs: the afterglow of a gamma-ray burst, a supernova amplified by a magnetar (neutron star with a strong magnetic field), or a failed supernova of the Ia type.

Then came Kepler with his precise, continuous measurements that allowed astronomers to record more details of the FELT event. "We have an impressive light curve," said Armin Rest of the Space Telescope Science Institute, Baltimore, Maryland. "We were able to limit the mechanism and properties of the explosion, we could exclude alternative theories and come to explain the dense shell model, which is a new way for massive stars to die and distribute matter into space."

"With Kepler we are now really able to connect the models with the data, "he continued." Kepler just makes the difference here. When I saw the Kepler data for the first time and realized how short that transient is, my jaw dropped. I said, "Oh wow!"

"The fact that Kepler has fully grasped the rapid development really limits the exotic ways in which stars die, and the wealth of data allowed us to unravel the physical properties of the phantom beam, for example, how much of the material Star at the end of his life, and the hypersonic velocity of the blast, this is the first time that we can test FELT models with a high degree of accuracy and combine theory with observations, "said David Khatami of the University of California at Berkeley.

This discovery is an unexpected consequence of Kepler's unique ability. This ability is needed for Kepler to discover extrasolar planets that pass shortly before their host stars and temporarily dim the starlight by a small percentage.

The Kepler observations indicate that the star ejected the shell Less than a year before it became a supernova, there is a glimpse of poorly understood fatalities of stars – the FELTs apparently come from stars that are about to die Dying to Make "Near-Death Experiences" Before They Explode

The science team's study appears on March 26, 2018 in the online edition of Nature Astronomy .

Rest says the next steps will be to find more of these items in the ongoing K2 mission or in the next mission of this type, TESS. This will allow astronomers to launch a follow-up campaign spanning different wavelengths, limiting the nature and physics of this new kind of explosion.

Further information:
For the first time caught: The early lightning of an exploding star

Further information:
A Fast-developing Radiant Transient Discovered by K2 / Kepler Nature Astronomy (2018) DOI: 10.1038 / s41550-018-0423-2, https://www.nature.com/articles/ s41550-018 -0423-2

Nature Astronomy

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