Hubble’s detailed image of the spiral galaxy ESO 422-41 highlights both its star-studded nature and its historical significance for astronomical research.

The Hubble Image of the Week shows spiral galaxy ESO 422-41, located about 34 million light-years from Earth in the constellation Columbus. The jagged, star-filled structure of the galaxy’s spiral arms and the glow of its dense core are shown here in intricate detail by Hubble’s Advanced Camera for Surveys. But images of this galaxy have a long history.

Historical context of astronomical observations

The name ESO 422-41 comes from its designation in the European Southern Observatory’s Southern Sky Atlas (B). In the days before automated sky surveys by space-based observatories such as ESA’s Gaia, many stars, galaxies and nebulae were discovered through large-scale photographic surveys.

Astronomers used large, state-of-the-art telescopes of the time to take hundreds of photographs covering a specific area of ​​the sky. They then tried to catalog all the new astronomical objects discovered by examining the resulting photographs.

Advances in astronomical technology

In the 1970s a new telescope at ESO’s La Silla facility in Chile carried out a survey of the southern sky, which had not yet been explored as thoroughly as the northern sky. The main technology for recording images at the time was glass plates treated with chemicals. The resulting collection of photographic plates became the ESO Southern Sky Atlas (B).

By examining the plates together, astronomers from ESO and Uppsala in Sweden recorded hundreds of galaxies (ESO 422-41); Only one of these is a cluster of stars and nebulae. Many were new to astronomy.

The evolution of shooting the sky

Since then, astronomical sky surveys have progressed from digital computer surveys such as the Sloan Digital Sky Survey and Legacy Surveys to surveys by space telescopes such as Gaia and the Wide Field Infrared Survey Explorer.

Despite this, photographic surveys of the sky have contributed greatly to astronomical knowledge for decades, and glass plate archives serve as an important historical reference for large areas of the sky. Some of these are still actively used today, for example, to study time-varying stars. And the objects discovered by these studies, including ESO 422-41, can now be examined in depth with telescopes such as Hubble.