Undergraduate student may have solved puzzle regarding isolated galaxies that have stopped producing stars

An undergraduate astrophysics student at UC Berkeley has found three unusual galaxies—cataloged as Shapiro Dwarf Galaxies I, II and III. Each galaxy is far from other galaxies and has stopped making stars, a combination that is extremely rare. The discovery, published in The Astrophysical Journal, provides compelling observational evidence of a long-held astronomical theory.

“Dwarf galaxies exist both in isolation and as satellites around larger galaxies like our own Milky Way,” said Julian Shapiro, the study’s sole author, who conducted his research while still in high school. “In isolation, these galaxies are expected to be actively forming stars, as there are no larger galaxies to strip their star-forming gas, but the galaxies I discovered break this rule.

“My paper argues that they may be among the first resolved ‘backsplash’ galaxy candidates, or galaxies that once passed close to a large neighbor, whose pressure removed their gas, before being flung outward.”

Isolated galaxies with no new stars

Usually, small dwarf galaxies found in isolated, low-density regions of deep space still contain cold gas that allows them to produce stars. Conversely, dwarf galaxies that have stopped forming stars—or have become “quenched”—are usually found in dense environments or near larger host galaxies, where strong hydrodynamic and gravitational forces siphon off their gas.

The three dwarf galaxies Shapiro discovered present a puzzle: They are both isolated and quenched. Astrophysicists have been attempting to explain what causes these two traits to coexist.

Shapiro believes the three dwarf galaxies once plunged through the gravitational well of a massive host galaxy—with Messier 101, known as the Pinwheel Galaxy, being the primary candidate—where environmental forces violently stripped away their star-forming gas before flinging them out into deep space. Alternatively, Shapiro Dwarf Galaxy II lies close enough to spiral galaxy NGC 5585 to possibly be a faint satellite rather than a backsplash galaxy.

The standard cosmological model, referred to as lambda-cold dark matter (ΛCDM), predicts that backsplash galaxies should be common, but identifying examples in the local universe has proven elusive. Shapiro’s findings show that the standard physics model likely holds true even in milder cosmic neighborhoods while offering individual candidates to be confirmed through follow-up observations. The paper also lends credence to the hypothesis that external forces must be responsible for stripping isolated, quenched galaxies of their star formation ability.

Simulations guide the search

Shapiro used simulations to determine where backsplash dwarf galaxies were most likely to exist near a Milky Way–like galaxy and where the telescope archives could detect them. His paper proposes new methods for predicting the frequency of these galaxies.

“Building the foundational knowledge necessary to detect the galaxies, develop modeling and analysis code, and analyze the results in comparison to our cosmological model was a challenge,” said Shapiro. “I was fortunate that many of the leading journals in the field are free to access, which helped me gain an understanding of the necessary techniques and background.”

Much of Shapiro’s research was spent estimating distances to determine whether the dwarf galaxies were truly isolated. He hopes that follow-up measurements from high-resolution space telescopes will definitively map the exact positions of the dwarf galaxies and rule out alternative scenarios for their quenched conditions. Shapiro expects that the new Vera C. Rubin Observatory will reveal many potential backsplash galaxies like the ones he uncovered.

High school research earns recognition

It is rare for any undergraduate student to publish their own research, but Shapiro’s case is especially notable as he originally conducted his research while in high school. Now in his first semester at Berkeley, Shapiro is taking astrophysics courses—along with some math and physics requirements—in pursuit of an eventual major.

“I envision my work serving as inspiration for young people aspiring to pursue research in astrophysics,” said Shapiro. “Often, school curriculums provide limited introductions to astronomy, and it is difficult for students to find mentorship and build experience in the field. My paper demonstrates that public archival telescope data is a critical tool for new discoveries in our understanding of cosmology and how our universe evolved, and that young astronomers are capable of uncovering these findings.”

The Davidson Institute recognized Shapiro’s backsplash galaxy research by naming him a 2026 Davidson Fellow. He also won the Astronomical League’s National Young Astronomer Award in 2025.

Celebrated Berkeley astronomy professor Alex Filippenko praised the advanced manner in which Shapiro conducted his research and analyzed his findings.

“Julian conducted some remarkably sophisticated research while still in high school, which is highly unusual and was recognized with the prestigious Davidson Fellowship,” said Filippenko. “I feel very fortunate that he chose UC Berkeley for his undergraduate studies in astrophysics, and especially that he decided to join my research team.”

Shapiro will work with Filippenko’s research group to study the Hubble tension—a scientific disagreement over the universe’s rate of expansion. He is also hoping to conduct follow-up observations of the Shapiro Dwarf Galaxies.

Who’s behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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