Supernova: Hubble captures stunning video of the death throes of a star

NASA‘s Hubble Space Telescope has captured the explosive final moments of a star as it goes supernova in a galaxy 70 million light years from the Earth.

Astronomers from Johns Hopkins University used images from the space telescope to track the fading light of the supernova to the spiral galaxy NGC 2525.   

The supernova, formally known as SN2018gv, was first spotted in mid-January 2018 in the constellation of Puppis in the Southern Hemisphere.

The team created a time-lapse video using images of the supernova taken between February 2018 and February 2019 and show it gradually fading to obscurity.

At its peak the explosion would have been up to five billion times brighter than the Sun, eclipsing all other stars and galaxies around it. 

The supernova, within galaxy NGC 2525, appeared like a very bright star located on the outer edge of one of its spiral arms when it was first observed. 

Astronomers working on a project to measure the expansion rate of the universe first pointed Hubble towards the supernova in February 2018.

Supernovae like this one can be used as cosmic tape measures, allowing astronomers to calculate the distance to their galaxies.  

Nobel Laureate Adam Riess from John Hopkins University used this supernova as a ‘candle’ to mark a point in space as part of the measurement of the expansion rate.

‘No Earthly fireworks display can compete with this supernova, captured in its fading glory by the Hubble Space Telescope,’ Riess said.

Supernovae are powerful explosions which mark the end of a star’s life and this explosion is what is known as a Type 1a supernova.

This type of cosmic firework display originates from a white dwarf star that is in a close binary system accreting material from its companion star. 

If the white dwarf reaches a critical mass  – 1.44 times the mass of our Sun – then its core becomes hot enough to ignite carbon fusion.

This triggers a runaway process that fuses large amounts of oxygen and carbon together in a matter of seconds and the energy released ‘tears the star apart’.

Matter is ejected from the star in a violent explosion – reaching speeds of up to 6 per cent of the speed of light and emitting huge amounts of radiation.  

Type Ia supernovae consistently reach a peak brightness of 5 billion times brighter than our Sun before fading over time.

Because supernovae of this type produce this fixed brightness, they are useful tools for astronomers, known as ‘standard candles’, which act as cosmic tape measures. 

Knowing the actual brightness of the supernova and observing its apparent brightness in the sky, astronomers can calculate the distance to these grand spectacles and therefore their galaxies. 

Riess and his team combined the distance measurements from the supernovae with distances calculated using variable stars known as Cepheid variables. 

Cepheid variables pulsate in size, causing periodic changes in brightness. 

As this period is directly related to the star’s brightness, astronomers can calculate the distance to them.

The team are interested in accurately measuring the distance to these galaxies since it helps them better constrain the expansion rate of the universe.

This expansion rate is also known as the Hubble constant. 

This value accounts for how fast the universe is expanding depending on its distance from us, with more distant galaxies moving faster away from us. 

Since it launched, NASA/ESA’s Hubble Space Telescope has helped dramatically improve the precision of the Hubble constant. 

Results from the same observing program led by Riess have now reduced the uncertainty of their measurement to an unprecedented 1.9 per cent. 

Further measurements of the galaxy the supernova was found in will contribute to their goal of reducing the uncertainty down to 1 per cent.

Achieving this goal will allow them to pinpoint how fast the universe is expanding. 

A more accurate Hubble constant may uncover clues about the invisible dark matter and mysterious dark energy that make up the majority of our universe.