Gravitationally Lensed Supernovae

The recent triumphs of observational cosmology are staggering.

Driven by impressive developments in technology, and thanks to important intellectual insights, observations that map out the expansion of the Universe over its 14 billion years of existence have been carried out.

Pioneered by distance measurements of high-redshift Type Ia supernovae (SNe Ia) and confirmed by early Universe data from the Cosmic Microwave Background (CMB), we discovered that the expansion of the Universe started to accelerate about half-way through the look-back time to the Big Bang, suggesting the existence of dark energy.

At smaller scales, dark matter is needed to hold together structures like galaxies and clusters of galaxies. These findings led to the “standard model” of cosmology, known as ΛCDM, already the subject of two Nobel prizes.

However, the nature of both dark matter and dark energy remains a mystery, hence the need for both new theoretical and empirical insights. It is in that context that the “Hubble tension” has gained a lot of interest.

The expansion rate of the Universe, the Hubble constant, H0, measured in the nearby universe and the value inferred from CMB differ by 9%.

This discrepancy has been claimed to be statistically significant and the theoretical community is busy looking into new physics that could account for it.Given the potentially profound implications, this proposal puts forward an ambitious program using space observations of strongly lensed SNe Ia to either confirm or refute the cosmological origin of the Hubble tension and offer new tests of the ΛCDM paradigm.

Furthermore, observations of highly magnified SNe Ia will allow us to accurately test the validity of the “standard candle” nature of  SNe Ia as they are used as distance indicators,  key for precision cosmology and essential for our ability to understand if dark energy is equivalent with Einstein’s Cosmological Constant, Λ, or not.

Through studies of flux ratios of multiple images of strongly lensed SNe, we will also probe the density gradient and granularity of the matter in the inner cores of lensing galaxies, a sensitive probe of dark matter properties.

Last but not least, observations of lensed SNe offer unique insights into the properties of dust in the interstellar medium of high-z galaxies, important for extinction corrections in cosmology.