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A supernova surrounded by stars

Our physicists are part of an international team that has successfully used a first-of-its-kind technique to measure the expansion of the Universe.

Data from their research provides an insight into a longstanding debate in the field of astronomy and could also help scientists more accurately determine the age of the Universe.

Gravitational lensing

The team used gravitational lensing, where a distant object is magnified by the large mass of a foreground galaxy cluster, to chart the position of an exploding star called a supernova.

They predicted that the supernova, first discovered in 2014, would reappear in a new position in 2015, which was confirmed by observations.

By using the time delays between the appearances of the 2014 and 2015 images, the researchers were able to measure the expansion of the Universe - also called the Hubble constant - using a theory developed in the 1960s that had previously been impossible to use.

Expansion of the Universe

In astronomy, there are two precise measurements of the expansion of the Universe.

One measurement uses nearby direct observations of supernovae, while the second uses the radiation that began to stream freely through the Universe shortly after the Big Bang – called the cosmic microwave background.

However, these two measurements differ by about ten per cent, which has caused widespread debate among physicists and astronomers. If both measurements are accurate, it means current theories about the make-up of the Universe are incomplete.

Independent measurement

The latest research involving Durham addresses this problem by using an independent way to measure the expansion rate of the Universe.

This new measurement agrees more with measurements for the expansion of the Universe using the cosmic microwave background, but doesn’t rule out those involving nearby observations of exploding stars.

The researchers say that if future observations of gravitationally-lensed supernovae give a similar result, then it would identify an issue with the current supernova value.

Alternatively, it could affect our understanding of galaxy cluster dark matter – a material thought to be common in the Universe that provides the gravity to hold galaxy clusters, and any other objects in the Universe, together.

Find out more

Main banner image credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI).