June 18, 2021

The formation of the Universe can only be understood with time

Schematic representation of the expansion of the Universe throughout its history

Schematic representation of the expansion of the Universe throughout its history

Analysis of more than 1,000 supernova explosions has revealed that models for the expansion of the Universe better match the data when a time-dependent variation.

If shown to be correct with higher quality future data from the Subaru Telescope and other observatories, these results could indicate as yet unknown physics working on the cosmic scale, the NAOJ (National Astronomical Observatory of Japan) reports in a statement.

Edwin Hubble’s observations more than 90 years ago showing that the expansion of the Universe remains a cornerstone of modern astrophysics. But when you get into the details of calculating how quickly the Universe expanded at different times in its history, scientists have difficulties in obtaining theoretical models that coincide with the observations.

To solve this problem, a team led by Maria Dainotti, a professor at NAOJ and the SOKENDAI Graduate University for Advanced Studies, analyzed a catalog of 1,048 supernovae that exploded at different times in the history of the Universe. The team found that theoretical models can be matched with observations if one of the constants used in the equations, appropriately called the Hubble constant, is allowed to vary over time.

There are several possible explanations for this apparent change in the Hubble constant. A probable but boring possibility is that there are observation biases in the data sample. To help correct for possible biases, astronomers are using the Hyper Suprime-Cam instrument on the Subaru telescope to observe fainter supernovae over a wide area. The data from this instrument will increase the sample of supernovae observed in the early Universe and reduce the uncertainty in the data.

But if the current results are kept under further investigation, if the Hubble constant is changing, that opens the question of what is driving the change. Answering that question might require a new, or at least modified, version of astrophysics.

These results are published in the ‘Astrophysical Journal’.


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