Astronomers capture amazing first moments of a star’s death

30 Nov 2018

An exploding white dwarf hits a neighbouring star to cause a supernova, which appears to be the cause of SN 2018oh. Image: NASA/JPL-Caltech

An international team was lucky enough to see the first moments of a star dying in unprecedented detail.

It seems almost fitting that in the final days before the retirement of one of the greatest space telescopes of the 21st century, Kepler should spot the slide into death of a star hundreds of millions of light years away.

In a recently published study, an international team of researchers documented how the Kepler space telescope – in coordination with ground-based telescopes – detected the light emanating from a exploding star, otherwise known as a supernova called SN 2018oh.

“Kepler – in its final days before running out of fuel and being retired – observed the minute changes in brightness of the star’s explosion from its very beginnings, while the ground-based telescopes detected changes in colour and the atomic make-up of this dying star,” said Dr Brad Tucker from the Australian National University.

“With the combined data from these telescopes, astronomers achieved what they had hoped for – an unprecedented observation of the onset of a star’s death.”

Not your average supernova

Located 170m light years away, SN 2018oh is an example of a Type Ia supernova used by astronomers to measure the expansion of the universe and discover more about the nature of dark energy. Until the introduction of Kepler in 2009, it was nearly impossible to study the early stages of a star explosion.

Type Ia supernovae brighten over the course of a three-week period before gradually fading away. However, SN 2018oh brightened rapidly a few days after the initial explosion, three times faster than a typical supernova at this time period.

Observations using the Dark Energy Camera at Cerro Tololo Inter-American Observatory in Chile and the Panoramic Survey Telescope and Rapid Response System at Haleakala Observatory in Hawaii revealed the supernova to be a gleaming blue spectacle. This was during an intense period of its demise when it was extremely hot at a temperature of billions of degrees Celsius.

In trying to explain the cause of this supernova, Tucker said that theoretical models suggest an exploding white star which had exhausted its nuclear fuel hit a neighbouring star.

“It’s possible in the case of SN 2018oh that the shockwave from the exploding white dwarf ran into the companion star, creating an extremely hot and bright halo that accounts for the added brightness and heat we observed,” Tucker said.

He added that finding out the frequency and distribution of this kind of Type Ia supernova would help to refine the models used in cosmology to estimate the rate of expansion of the universe.

Colm Gorey was a senior journalist with Silicon Republic