Cosmic Community of Abell 1489

Punctuating the deep black of this Image of the Week are hundreds of blobs of light, each one an entire galaxy in our Universe. Many of the yellowish points are members of the galaxy cluster Abell 1489, imaged here using the Gemini Multi-Object Spectrograph (GMOS) on Gemini North, one half of the International Gemini Observatory, supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab.

Galaxy clusters are immense neighborhoods of galaxies gravitationally bound together. These massive formations serve as tools for astronomers to understand the Universe’s dark matter distribution, structure, and overall evolution. Astronomers classify galaxy clusters in several ways and have compiled multiple catalogs of clusters. This particular cluster has been labeled using the Abell classification scheme. Within this scheme, clusters are mainly sorted by their richness — the number of galaxies they contain — and their distance from us. Abell 1489 was categorized with a richness of Group 4. This means it has between 200 and 299 galaxies, which also makes it one of the richer clusters in the Abell catalogue.

Abell 1489 appears fainter in most telescopes than other galaxy clusters, indicating that the structure is immensely distant from Earth. Yet images like this demonstrate the sensitivity of instruments like GMOS to resolve this cluster’s distant light and reveal its richness. This abundance is of particular importance for future study: the mass of all these galaxies together makes this cluster behave as a ‘magnifying glass’ to view light sources that are even farther away. These effects of gravitational lensing are visible as arcs of light, such as in the upper middle section of this image. The Gemini telescopes are some of the few telescopes that can show lensing in such clarity.