NASA asks volunteers to find overlapping galaxies for cosmic dust research

NASA announced Overlap Zoo on September 30, 2026, inviting volunteers online to identify galaxies that appear to overlap in telescope images. The project aims to find pairs suitable for studying cosmic dust: light from a galaxy in the background can reveal dust in one closer to Earth. The classifications will help researchers select targets for later analysis; NASA has not reported results from the new project.

Participants will examine images that Galaxy Zoo volunteers previously flagged as possible overlapping pairs. Overlap Zoo teaches them to check whether a pair is present, classify features of each galaxy and mark their outlines. NASA says people can work through as many images as they like, with no prior experience required and an internet-connected computer sufficient to take part.

How overlapping galaxies reveal dust

An overlap is a matter of viewing angle: two galaxies line up along the observer’s line of sight. In a useful pair, the more distant galaxy provides a bright background against which dust in the nearer one appears as a darker silhouette. Researchers can study how that dust is distributed and how it blocks, scatters or dims light passing through it.

The technique has an established scientific basis. In a 2016 paper on the STARSMOG programme, astronomers B. W. Holwerda and W. C. Keel described using overlapping, or occulting, galaxy pairs to measure dust in foreground galaxies. They reported using Hubble Space Telescope observations to map that dust in fine detail. Their work provides context for the method; it does not report findings from Overlap Zoo.

Why Overlap Zoo needs volunteers

NASA says the growing number of galaxy observations makes it difficult for astronomers to classify every candidate pair themselves. Trevor Butrum, the project lead and a graduate student, said volunteers’ work would be valuable in creating a large, clean catalog for further analysis. Identifying a promising image is an early step: researchers would still need to determine which pairs can support the intended dust measurements.

Galaxy Zoo offers a precedent for large public classification efforts. Its project account says its first phase began in July 2007 with images of one million galaxies from the Sloan Digital Sky Survey. It reports receiving more than 50 million classifications from over 150,000 people in the first year. Those figures describe Galaxy Zoo’s earlier work, not participation in Overlap Zoo.

The new project builds directly on that earlier image sorting. Rather than asking volunteers to begin with an unfiltered collection, NASA says it presents possible overlaps already identified by Galaxy Zoo participants. The additional checks are intended to help distinguish useful galaxy pairs and record their visible features in a form researchers can assess.

What happens after the images are classified

NASA describes the goal as a catalog of galaxy pairs suitable for dust studies. Its announcement does not give a completion date, a count of finished Overlap Zoo classifications or a timetable for publishing the first catalog. It also reports no dust measurements produced by the new volunteer work. The immediate contribution is the identification and description of candidate systems for scientists to examine.

That distinction matters because an apparent overlap alone does not measure the amount of dust. The foreground galaxy must be assessed against light from the one behind it before researchers can map where dust lies or quantify how much it dims starlight. The STARSMOG paper shows what an analysis of suitable pairs can investigate; NASA presents Overlap Zoo as a way to help find more candidates for that kind of work.

For readers who want to participate, NASA directs volunteers to Overlap Zoo and says its instructions teach the classification task as they go. Each checked image can contribute to the search, but the scientific value of the resulting catalog will depend on the pairs researchers confirm and the analyses they subsequently report.