What is Gravitational Lensing?

January 10, 2025

Recent advancements in astrophysics have led to a groundbreaking discovery involving the identification of 44 previously unknown stars within a distant galaxy cluster. This research, conducted by the Centre for Frontier Science at Chiba University, Japan, and supported by over 45 international partners, utilised the James Webb Space Telescope (JWST) and a technique known as gravitational lensing. The findings provide vital information about the behaviour of stars during important period in the Universe’s history, referred to as “cosmic noon.”

Gravitational Lensing

Gravitational lensing is a phenomenon where a massive foreground galaxy cluster bends and magnifies the light from a more distant galaxy. This effect allows astronomers to study objects that would otherwise be too faint or distant to observe. In this case, the galaxy cluster Abell 370 acted as a lens, stretching the light from the Dragon Arc into an elongated shape, akin to a “hall of mirrors.”

The Role of the James Webb Space Telescope

The JWST played important role in this discovery. It provided high-resolution images over a year-long observation period. The telescope’s advanced capabilities allowed researchers to peer through cosmic dust, revealing hidden stars that were previously obscured. This technology has transformed our understanding of star formation in distant galaxies.

Identifying the Stars

The research team identified 44 stars based on their brightness variations during the study. These stars were confirmed as individual entities rather than clusters or supernovae. The size of the observed points, after accounting for lensing effects, indicated they were distinct stars, marking milestone in astronomical research.

Into Cosmic Noon

The term “cosmic noon” refers to a period approximately eight to ten billion years ago when star formation peaked in the Universe. The findings from this study provide a unique glimpse into the composition and behaviour of stars during this era. The research indicates that stars from this time behaved differently than those in the present day, contributing to our understanding of cosmic evolution.

The Importance of Red Supergiants

Many of the newly identified stars are classified as red supergiants. These massive stars are typically shrouded in cosmic dust, making them challenging to detect. The JWST’s capabilities allowed the research team to observe these stars more clearly, revealing their characteristics and contributing to our understanding of stellar evolution.

Abell 370 is a massive galaxy cluster that magnifies distant objects.
Cosmic noon refers to a peak period of star formation in the Universe.
Red supergiants are massive stars often obscured by cosmic dust.
The Dragon Arc is a distant galaxy observed through gravitational lensing.
The Centre for Frontier Science is based at Chiba University, Japan.

Future Research Directions

The research team plans to continue their observations of the Dragon Arc to distinguish between various stellar populations magnified by Abell 370. This ongoing study aims to deepen our understanding of star formation and the characteristics of galaxies during critical periods in cosmic history. The implications of this research extend beyond mere identification, as they offer a window into the processes that shaped the Universe as we know it .

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