Mar 26, 2024 - The James Webb Space Telescope, a marvel of international collaboration between NASA, ESA, and CSA, has unveiled a breathtaking new image of the galaxy I Zwicky 18 (I Zw 18). This image offers a spectacular look into the heart of a dwarf irregular galaxy, teeming with star formation and providing valuable insights into the early Universe.

A Galaxy Frozen in Time

Discovered in the 1930s by astronomer Fritz Zwicky, I Zw 18 resides roughly 59 million light-years from Earth. Unlike our majestic spiral Milky Way, I Zw 18 is a dwarf irregular galaxy, significantly smaller and lacking a well-defined structure. This characteristic makes it particularly intriguing, as it resembles the types of galaxies that populated the early Universe.

Starbursts and Dusty Bubbles

The image reveals a captivating scene. Two prominent starburst regions, evident as bright, white and blue lobes, reside at the galaxy's core. These regions are cradles of intense stellar activity, where new stars are born at a furious pace. The surrounding wispy brown filaments are bubbles of gas, sculpted and heated by the energetic winds and radiation unleashed by these young, hot stars.

A Companion's Influence?

Interestingly, a neighboring galaxy can be seen in the wider-field view. This companion galaxy might be playing a role in I Zw 18's recent star formation frenzy. Gravitational interactions between galaxies can trigger bursts of star formation, and this could be the case here.

Ancient Light and Modern Mysteries

The image also showcases a captivating background. The orange blobs scattered around I Zw 18 represent the faint glow of ancient, fully formed galaxies residing at much greater distances. Studying these distant galaxies alongside I Zw 18 allows astronomers to piece together the grand narrative of galaxy evolution across cosmic time.

Peering into the Stellar Cradle

This Webb observation is part of a program dedicated to studying the life cycle of dust within I Zw 18. Dust plays a crucial role in star formation, and by studying its properties at infrared wavelengths, Webb delves deeper than ever before. Notably, I Zw 18 possesses one of the lowest abundances of elements heavier than helium among local galaxies. This characteristic makes it a valuable natural laboratory, potentially mirroring the conditions present in the very first star-forming galaxies at high redshifts (greater distances and therefore looking back further in time).

Rewriting the Star Formation Story

Previously, I Zw 18 was thought to be a late bloomer, having only recently begun churning out stars. However, past observations with Hubble revealed the presence of fainter, older red stars. This discovery pushed back the estimated timeframe for star formation in I Zw 18 by at least a billion years, possibly even ten billion years. The new Webb data adds another layer of complexity. By analyzing the stellar populations within the two starburst regions, Webb suggests that these bursts occurred at different epochs. The evidence points towards a more recent starburst in the northwest lobe compared to the southeast lobe.

A Glimpse into the Early Universe

The James Webb Space Telescope's observations of I Zw 18 provide a captivating glimpse into the workings of a dwarf irregular galaxy. By studying its ongoing star formation, the properties of dust, and the unique stellar population, astronomers gain valuable insights into the processes that governed galaxy evolution in the early Universe. This is just the beginning of an exciting journey of discovery, as Webb continues to unravel the mysteries of I Zw 18 and other fascinating objects in the cosmos.

 Source - ESA