Astronomers using the NASA/ESA Hubble Space Telescope have tracked the fading light of a Type Ia supernova in NGC 2525, a barred spiral galaxy located approximately 70 million light-years away in the southern constellation of Puppis.
Hubble began observing a supernova called SN 2018gv in February 2018, after it was first detected by amateur astronomer Koichi Itagaki a few weeks earlier in mid-January.
“No Earthly fireworks display can compete with this supernova, captured in its fading glory by Hubble,” said Professor Adam Riess, a Nobel laureate and a researcher at the Space Telescope Science Institute and Johns Hopkins University and leader of the High-z Supernova Search Team and the Supernovae H0 for the Equation of State (SH0ES) Team.
Type Ia supernovae like SN 2018gv originate from a white dwarf 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), its core becomes hot enough to ignite carbon fusion, triggering a thermonuclear runaway process that fuses large amounts of oxygen and carbon together in a matter of seconds.
The energy released tears the star apart in a violent explosion, ejecting matter at speeds up to 6% 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.
Professor Riess and colleagues 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: allowing them to act as another ‘standard candle’ in the cosmic distance ladder.
The researchers are interested in accurately measuring the distance to these galaxies since it helps them better constrain the expansion rate of the Universe, 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.