The Magellanic clouds, seen here above Paranal Observatory in Chile, are due for a name change, some astronomers say.Juan Carlos Munoz-Mateos/ESO

The Small Magellanic Cloud (SMC), a hazy blob in the night sky easily visible to people in the Southern Hemisphere, has long been considered a lone dwarf galaxy close to the Milky Way. But a study posted online this month, and accepted by The Astrophysical Journal, suggests the familiar site is not a single body, but two, with one behind the other as viewed from Earth.

By tracking the movements of clouds of gas within the SMC and the young stars recently formed within them, astronomer Claire Murray of the Space Telescope Science Institute and her colleagues have found evidence of two stellar nurseries thousands of light-years apart. If confirmed, the reassessment will likely amplify calls from an increasing number of astronomers to change the SMC’s name and that of its neighbor, the Large Magellanic Cloud (LMC).

Sixteenth century Portuguese explorer Ferdinand Magellan, after whom the galaxies are named, was not an astronomer, did not discover them, and is recorded as having murdered and enslaved Indigenous people during his first-ever circumnavigation of the globe. As a result, astronomer Mia de los Reyes of Amherst College called for renaming the SMC and LMC in an opinion piece for Physics magazine in September. The idea has since “gotten a lot of informal support,” she says.

The two Magellanic clouds are in the gravitational sway of the much larger Milky Way and are on course to pass through it in the future. The LMC is a disk galaxy, like the Milky Way in miniature. But the SMC is irregular in shape, two-thirds of the LMC’s mass, and often gets overlooked in favor of its heftier neighbor. “The SMC got the short end of the stick,” de los Reyes says. “It’s less well modeled.”

Some previous studies have suggested there may be multiple components to the SMC, but the truth has not been easy to pin down. The SMC “has suffered most” in its gravitational interactions with the LMC and the Milky Way, Murray says. “It’s simply full of disrupted gas. It’s a train wreck of sorts.”

So, she and her team set out to reinvestigate both the system’s stars and its gas, using what Murray calls the “latest and greatest” instruments available. To probe the SMC’s gas they turned to the Australian Square Kilometre Array Pathfinder, a radio telescope made up of 36 dishes each 12 meters in diameter. With it, they zoomed in on radio waves emitted by atomic hydrogen gas. They then plotted the location and velocity of thousands of the SMC’s young stars of less than 10 million years in age, using Gaia, an orbiting observatory from the European Space Agency. Over the past decade, Gaia has logged such data for more than 1 billion stars across the Milky Way with unprecedented accuracy.

Combining those two sets of data and assuming any stars that young would still be moving in concert with the clouds of gas from which they formed, they identified two distinct star-forming clouds with different levels of heavy element enrichment. By measuring how much light from the two clouds is absorbed by dust between them and Earth, they calculated that one is more distant than the other. But determining the amount of separation proved tricky. “Measuring distance to gas is very challenging,” Murray says. In the new study, her team describes constructing a simple computer model of the system. With the available data plugged in, it predicts the two clouds are 16,000 light-years apart—more than half the distance between Earth and the center of the Milky Way.

This view of the SMC “is much more compelling” than previous attempts to untangle its parts, de los Reyes says, and relies on “better data.”

The question remains over whether these are two separate objects that have drifted close together by their mutual gravity or whether one is debris drawn from the other by a close encounter with another galaxy such as the LMC. That the two parts seem to contain similar masses of gas is “suggestive of two systems” without a connection, Murray says. But de los Reyes counters that the level to which previous generations of stars have enriched the two gas clouds with heavier elements is “relatively similar,” suggesting they are “not entirely unrelated.”

If further studies confirm that the SMC is not one thing, but two, a new name or names will be in order. De los Reyes argues that whatever the clouds are called, astronomers need to oust Magellan. She points out that the objects had been known and described by peoples in the Southern Hemisphere for thousands of years, as well as recorded by Italian and Arabic explorers before Magellan’s voyage.

The astronomical community has embraced Magellan in other ways. There are craters on the Moon and Mars named in his honor, NASA’s Magellan mission to Venus, and the twin Magellan Telescopes in Chile and the Giant Magellan Telescope currently under construction there. De los Reyes says the atrocities that Magellan and his crews committed in Argentina, Guam, and the Philippines during their travels make him an unsuitable candidate for these honors and for having his name inscribed in the more than 17,000 peer-reviewed papers on topics related to his namesakes.

De los Reyes is now working with the International Astronomical Union (IAU), which manages the naming of celestial objects, to present a resolution to its general assembly in Cape Town, South Africa, in August 2024. But what to call the familiar clouds? Murray suggests one of their many Indigenous names. De los Reyes says the IAU resolution will include several options for members to vote on. She likes the idea of keeping the acronyms SMC and LMC—“to maintain continuity in the literature”—and just changing the “M” to something “more physically meaningful” such as “milky” to tie in with the Milky Way, or “meridional” which can refer to southern things.