Understanding Gravitational Lensing

Simply put, gravitational lensing is a phenomenon where a massive body, like a galaxy, a cluster of galaxies, or a black hole, creates a gravitational field that distorts and magnifies the light from objects situated behind it.

• This phenomenon is a direct result of Einstein’s theory of general relativity, which posits that mass can bend light.
• Gravitational lensing is a powerful tool for astronomers as it assists in the study of black holes, dark matter, and other celestial phenomena.
• Similar to how a camera lens or magnifying glass works, gravitational lensing bends light rays that pass through it, focusing the light elsewhere. This process is known as refraction.
• Currently, scientists from across the globe are conducting three major gravitational lensing experiments. The most extensive of these is the Hyper Suprime-Cam (HSC) Survey.
• The observations were made using the Hyper Suprime-Cam (HSC), one of the most powerful astronomical cameras in the world, located atop the 8.2m diameter Subaru Telescope on Mauna Kea in Hawai’i.

Unveiling the Experiment Details:

• Dark energy and dark matter combined make up 95% of the known universe.
• Despite its prevalence, very little is known about the nature of dark matter or how it has evolved over time.
• A team of astrophysicists and cosmologists, including Dr. Surhud More from the Inter-University Center for Astronomy and Astrophysics (IUCAA), successfully characterized the structure of dark matter.
• The team made use of images captured by the Subaru telescope in Hawai’i.
• The team’s research helped them conclude that the 'clumpiness' of matter is less than what was previously estimated based on observations of the Cosmic Microwave Background (CMB) in the universe.

Discover more about dark matter in the linked article.

The Findings and Their Methodology:

• The team measured the 'clumpiness' (referred to as S8 by scientists) of the universe and found it to be 0.76, which is consistent with findings from other gravitational lensing surveys.
• However, this value contrasts with the S8 value of 0.83 predicted by the Cosmic Microwave Background, dating back to the universe's origins approximately 380,000 years ago.

The Significance of These Findings:

• Understanding the density and 'clumpiness' of dark matter is crucial for unraveling how the structure of the universe has evolved over time.
• By mapping dark matter in a tomographic (3D) manner, we are now able to test the cosmological model more rigorously.