New type of exploding star observed

The Kepler Space Telescope has enabled astronomers to study a new kind of exploding star.

FELT

An artist’s depiction of a FELT event. In the left image, a dying red star ejects mass into space. This creates a shell around the star. In the centre image, the star’s core explodes. In the right image, the supernova shockwave hits the shell, converting the energy into a burst of light. Image Credit: NASA, ESA, and A. Feild (STScI)

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Astronomers have been able to analyse a new type of stellar explosion that had previously eluded detailed observation.

Known as a FELT (Fast-Evolving Luminous Transient), these phenomena are a newly discovered kind of supernova, or exploded star.

NASA’s Kepler Telescope – normally used to search for planets orbiting stars outside our Solar System – has been used to view these events and enable astronomers to learn more about them.

FELTs are supernovae that get a brief but powerful boost in brightness.

The cause of this flash is a star that collapses and explodes as a supernova, but on these occasions the star is enclosed in one or more shells of gas and dust.

Energy from the explosion hits the shell, and the energy is converted into light.

This burst in radiation last just a few days, which is about 10 per cent of the length of a typical supernova.

Due to their brevity, only a few have been seen in past sky surveys.

But Kepler collects data on a patch of sky every 30 minutes, meaning it is able to observe FELTs that might be missed by other surveys.

Kepler observations also revealed that the stars in question eject the shell of matter less than a year before going supernova.

This means that FELTs occur in stars that eject shells of matter in mini eruptions shortly before they explode.

“We collected an awesome light curve,” says Armin Rest of the Space Telescope Science Institute.

“We were able to constrain the mechanism and the properties of the blast.

We could exclude alternate theories and arrive at the dense-shell model explanation.”

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“This is a new way for massive stars to die and distribute material back into space.