Supernova analysis points to variable dark energy
More and more analyses indicate that dark energy is not constant – with potentially far-reaching consequences. Now a supernova study has been added.
The supernova 1994D at the galaxy NGC 4526
(Image: NASA/ESA, The Hubble Key Project Team and The High-Z Supernova Search Team)
The largest standardized database of type Ia supernovae has now provided the next clue that the mysterious dark energy is changing as the universe evolves. The Supernova Cosmology Project's discovery is not yet confirmed, but it could be another piece of the puzzle on the way to what could be the biggest discovery in cosmology for decades. If confirmed, it would be a "dramatic departure from Albert Einstein's cosmological constant" and a deviation from the standard model of cosmology, as the research team explained.
The evidence is mounting
For their analysis, the research group compared a total of 2087 type Ia supernovae and compiled them in a standardized database called "Union3". The predecessor from 2010 only contained 557 of these special stellar explosions. They are of particular interest to researchers because they are very predictable and have a consistent brightness, which makes them so-called standard candles. This means that they can be used for cosmic distance measurements over particularly large distances. Union3 can be used to look back about seven billion years, the team explains.
The investigation of the database has now revealed "indications" that dark energy changes over time. However, they are not clear enough to say definitively that it has become weaker. But they would point in the same direction as a finding by the Dark Energy Spectroscopic Instrument (DESI) , which caused a stir last year. Further analysis of supernovae also seems to support this conclusion. Nobody is "jumping around enthusiastically" yet, says Nobel Prize-winning physicist Saul Perlmutter, who was involved in the Union3 study. But people are at least sitting up in their chairs. It is exciting that we are now reaching a level of precision "where it gets interesting".
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Far-reaching consequences possible
If – the influence of dark energy decreases over time, as suggested in the paper now published in The Astronomical Journal –, this would have significant consequences. This is because the balance between normal matter and dark energy determines, among other things, the fate of the cosmos as a whole. This balance is the fundamental component for the expansion of the universe. Even the currently accepted values for the age and size of the universe could then be incorrect. The first indications of the variability of dark energy weregathered by the DESI in the first year after its commissioning.
If the evidence is further confirmed, it could be the biggest discovery in the exploration of the cosmos for more than a quarter of a century. After Edwin Hubble and others first proved at the beginning of the 20th century that the universe was expanding, researchers long assumed that this expansion was slowing down. It was not until 1998 that the analysis of distant supernovae revealed that, on the contrary, the expansion was actually accelerating. In 2011, the Nobel Prize in Physics – was awarded to Perlmutter and others for this discovery. Dark energy is said to be responsible for this acceleration. However, the possible discovery now makes it clear just how mysterious its nature still is.
(mho)
