Our next event is a plenary talk by Marcelle Soares-Santos on Cosmology in the era of Multi-Messenger Astronomy.
Note the title slide shows a rare binary merger.
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Two ways to measure the expansion rate of the universe (supernova and CMB), and thus the age of the universe have a building discrepancy. Finding new ways to measure the age of the universe is becoming more and more important to determine which method is correct.
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The Dark Energy Survey (DES) seeks to combine multiple Dark Energy Probes, rather than using a single probe. Results include data on the cosmic shear, galaxy-galaxy lensing, and galaxy-galaxy clustering.

If you're interested in learning more about the Dark Energy Survey, beyond this thread, check out their website!
https://www.darkenergysurvey.org/ 
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Binary systems, like the own showed in the 1st tweet in this thread, are difficult to find. There are two signatures used to make this search easier, including relativistic outflows and sub-relativistic outflows.
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When gravitational waves are detected, we can't know exactly where they originated from. Dr. Soares-Santos and her team were able to identify a merging event (shown in first tweet in this thread) as the source behind gravitational waves.
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The main source of gravitational waves is black-hole black-hole merging event, but these merging events are difficult to detect. Are there other counterparts to a black-hole merging event, that would be easier to detect? Ongoing research suggests not (for now).
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How can we connect blackhole merging events to cosmology? We can combine merging events to constrain the Hubble constant, as described by Palmese et al. (2020)
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The more merging events we can detect, the better we can constrain the Hubble Constant, and therefore the age of the universe. According to this figure, we should have a well constrained value by *2023.*

In summary, monitoring merging events can be used as a new technique to determine the Hubble Constant and the rate our universe is expanding. This is important, because supernova and CMB based measurements have a growing discrepancy.
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