An international team including Lancaster astrophysicists have analysed the first light of a supernova which exploded about 170 million years ago, the light from which reached Earth in early 2018.

Along with Dr Jakob Nordin, a collaborator at Humboldt University of Berlin, Dr Steven Williams and Professor Isobel Hook obtained and analysed follow-up observations from the European Southern Observatory's New Technology Telescope (NTT) in Chile, as part of the ePESSTO project (www.pessto.org).

The All-Sky Automated Survey for Supernovae first detected the supernova (named SN 2018oh) from the ground, which was then followed by telescopes across the world.

Once the data from NASA’s Kepler space telescope (now retired) were received, they revealed the first moments of the explosion. This enabled astronomers to observe the supernova explosion as part of a unique scientific experiment.

SN 2018oh is an example of a Type Ia supernova — the kind that astronomers use to track the expansion of the universe and probe the nature of the invisible “dark energy” that makes up a large fraction of our Universe.

Astrophysicist Dr Steven Williams from Lancaster University said: "Compared to what we normally expect in a Type Ia supernova, SN 2018oh shows excess emission at early times. This reveals that there is additional energy being released shortly after the explosion.”

“Currently, astronomers are uncertain as to what causes this, but one possibility is that the material ejected in the explosion may be interacting with a companion star to the exploding white dwarf.”

A white dwarf is the remains of a star that has ceased nuclear burning, leaving behind a dense core made up of carbon and oxygen. If the white is massive enough it can then explode as a Type Ia supernova.

"Another possibility is that there is extra nickel-56 in the outer layers of the ejected material. The radioactive decay of this nickel isotope powers the light curves of these types of supernova explosions, and is the reason they are so luminous. If there was extra nickel-56 in the outer layers, this would make the supernova brighter than would otherwise be expected shortly after explosion."

Three research papers by 130 scientists attempt to explain the resulting unusual data revealed in the details of SN 2018oh, which lies in the spiral galaxy UGC 4780 in the Cancer constellation.

One of the papers has been accepted for publication in The Astrophysical Journal Letters, while the other two have been accepted to The Astrophysical Journal.

The authors of these papers include scientists from dozens of institutions, including members of the Kepler team. Additional observatories providing valuable data to support the experiment include the NTT, Las Cumbres Observatory, a global network of robotic telescopes based in Goleta, California; Tsinghua-NAOC and Lijiang Telescopes in China; Konkoly Observatory in Hungary; Lick Observatory on Mount Hamilton in California; Las Campanas Observatory in Chile, and others.

NASA's Ames Research Center in California’s Silicon Valley manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.