New study identifies hundreds of previously undocumented satellite systems orbiting dwarf galaxies

Rather than focusing on large galaxies like the Milky Way, a new survey dramatically shifts the focus to dwarf galaxies.
UPDATED AUG 7, 2025
The Milky Way has a number of satellite galaxies, but the biggest one is the Large Magellanic Cloud (Representative Cover Image Source: NASA)
The Milky Way has a number of satellite galaxies, but the biggest one is the Large Magellanic Cloud (Representative Cover Image Source: NASA)

A groundbreaking new study led by astronomers at Dartmouth has vastly expanded our knowledge of galactic ecosystems, identifying hundreds of potential satellite galaxies orbiting dwarf galaxies. The multi-institutional team's findings, published in The Astrophysical Journal, challenge existing assumptions about how these smaller galaxies are formed and how they interact with their environments, according to Dartmouth

Candidate satellite galaxies for a dwarf galaxy called ESO486-G21 (Image Source: Dartmouth | Laura Hunter)
Candidate satellite galaxies for a dwarf galaxy called ESO486-G21 (Image Source: Dartmouth | Laura Hunter)

Traditionally, most research on galactic satellites has focused on large galaxies, such as the Milky Way. However, this new survey dramatically shifts the focus to dwarf galaxies, systems that are less than a tenth the size of our galaxy. The study nearly triples the number of dwarf galaxies that have been surveyed for satellites, providing a massive new dataset for astronomers to analyze. 

Our galaxy, the Milky Way, is typical: it has hundreds of billions of stars, enough gas and dust to make billions more stars, and at least ten times as much dark matter as all the stars and gas put together (Cover Image Source: NASA)
Our galaxy, the Milky Way, is typical: it has hundreds of billions of stars, enough gas and dust to make billions more stars, and at least ten times as much dark matter as all the stars and gas put together (Image Source: NASA)

The survey identified 355 candidate satellite galaxies, with 264 of these being previously uncatalogued. Researchers suggest that 134 of the candidates are highly likely to be true satellite galaxies. “This project fills a critical gap, offering fresh insights into the process of how galaxies form and their connection to dark matter," said author Burçin Mutlu-Pakdil, an assistant professor of physics and astronomy." Our goal is to build a statistical sample of the smallest galaxies in the universe, as they are the most dominated by dark matter and serve as clean laboratories for understanding its nature.” 

The survey, led by postdoctoral fellow Laura Hunter, analyzed publicly available imaging data from the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys. The team used an algorithm to identify potential satellites and then visually inspected each candidate to ensure accuracy. By studying these systems, the research aims to unlock clues about conditions in the early universe and how galaxies evolve. Previous studies of larger galaxies have suggested a correlation between a host galaxy's size and the number of satellites it possesses. The new data will enable scientists to test whether this principle applies to the much smaller dwarf galaxies. 

Hubble displays a dwarf spiral galaxy (Image Source: NASA/ESA)
Hubble displays a dwarf spiral galaxy (Image Source: NASA/ESA)

Hunter explains, “Astronomy is a field where you can’t run experiments; all you can do is observe and make as many measurements as you can," and "then put that data into a simulation and see whether it reproduces your observations. If it doesn’t, that tells us that there’s something wrong with our assumptions or our model of the universe.” This new survey is the initial phase of a broader effort. The research team is currently conducting a follow-up campaign to confirm the candidates and analyze their properties, such as size, gas content, and star formation rates. This work is expected to have a significant impact on our understanding of dark matter and the formation of galaxies on the smallest scale. 

The Dartmouth team's work to understand how galactic interactions influence satellite formation is complemented by detailed observations of individual systems. A prime example is the dwarf galaxy NGC 4449, which the NASA/ESA Hubble Space Telescope recently focused on. Located just 12.5 million light-years away in the constellation Canes Venatici, this small but mighty galaxy is a prime example of a "starburst galaxy," a system undergoing an extraordinary period of star creation. The dwarf galaxy's proximity to Earth makes it an ideal cosmic laboratory for studying how these gravitational encounters fuel the creation of new stars and shape galactic evolution, providing a valuable case study for the statistical data gathered by the Dartmouth team. 

MORE STORIES

Comet C/2025 N1 (ATLAS) is on a hyperbolic trajectory; it will pass through our solar system only once before exiting forever.
1 day ago
A new study suggests our planet's crust holds chemical clues to its cosmic journeys.
1 day ago
Scientists have analyzed rocks from the crater floor, uncovering a diverse set of minerals that tell the story of a complex history of water-rock interactions.
5 days ago
Critical data from global observatories like the European Southern Observatory's (ESO) Very Large Telescope has unveiled new challenges for the 2031 rendezvous.
5 days ago
This achievement is a significant step in humanity's quest to answer one of the most fundamental questions: "Are we alone?"
5 days ago
The Moon is slowly drifting away from Earth, a continuous process driven primarily by the gravitational tug-of-war between our planet's oceans and its lone natural satellite.
5 days ago
Gravity is the force behind tidal locking, but the Moon's unique case is rooted in a cataclysmic event.
6 days ago
For decades, thick clouds of gas and dust have obscured the true three-dimensional shapes of these stellar nurseries, making them notoriously difficult for scientists to study.
7 days ago
After capturing a second visible-light aurora from the planet's surface, NASA's Perseverance rover confirmed the breakthrough.
Sep 16, 2025
NASA has discovered a Martian rock sample containing mineral and organic signatures that, on Earth, are found almost exclusively with biological activity.
Sep 16, 2025