Do grey aliens live on one of these 1500 Earth-like planets?

Backyard Worlds keeps turning up objects that sit right on the line between planets and stars, and the citizen scientists who sift through the data keep proving they belong in the conversation. The project’s early haul of roughly 1,500 brown dwarfs has grown past three thousand in a decade, and the newest batch includes objects cold enough that liquid water could plausibly exist on their surfaces. That detail alone keeps the grey-alien speculation alive without stretching the facts.

Citizen astronomers

Backyard Worlds: Planet 9 began as a Zooniverse collaboration between NASA scientists and volunteers who review images from NEOWISE, the retired Spitzer telescope, and NOIRLab facilities. The original volunteer pool was described as more than 100,000; current estimates place active participation near 200,000. Over ten years the group has logged millions of classifications and produced a 2026 paper in The Astronomical Journal that lists 61 citizen scientists among its 75 authors. The same platform still hosts fresh data releases, so the workflow that started the project continues without interruption.

Space dwarfs

Brown dwarfs form hot and then cool across cosmic time, drifting through a temperature range that lands between gas-giant planets and the smallest stars. The expanded catalog now exceeds three thousand objects, many of them within a few dozen light-years of the Sun. Astronomers estimate one brown dwarf for every three to four stars in the solar neighborhood, a ratio that revises earlier tallies and places more potential hosts for complex chemistry closer than previously counted.

A discovery of great importance

Many of the new finds sit below the boiling point of water, allowing water-cloud decks to form in their atmospheres. Aaron Meisner, an astronomer on the team, noted that these cool worlds give researchers fresh laboratories for studying planetary formation and atmospheric physics beyond our solar system. The record holder remains WISE 0855, first measured at roughly minus ten degrees Fahrenheit. JWST NIRSpec observations taken in 2024 captured its spectrum from one to five microns, refined temperature estimates, and confirmed carbon-monoxide absorption consistent with vertical mixing. Those data place WISE 0855 in clearer context among the growing population of cold brown dwarfs rather than treating it as an isolated anomaly.

Contributions from viewers like you

The 2026 paper demonstrates that volunteers are no longer simply classifiers; they appear as co-authors on peer-reviewed work and have driven several of the project’s landmark results. Two participants have since moved into professional astronomy roles, and nine others have earned co-author credits on additional Astrophysical Journal papers. The sustained effort across a full decade shows that distributed human review still outperforms current AI tools when the task is spotting faint, slow-moving sources in archival images.

Project Evolution and Spin-Off Initiatives

After the initial success, the team launched dedicated follow-on efforts. Backyard Worlds: Cool Neighbors began in mid-2023 and pairs machine-learning filters with volunteer review to target even colder objects. Backyard Worlds: Binaries concentrates on ultracool companions and wide-orbit systems. Both projects continue to upload new data sets, keeping the original volunteer base engaged while expanding the types of discoveries the community can pursue.

JWST Observations of the Coldest Brown Dwarfs

Beyond WISE 0855, JWST has targeted other Y-dwarfs such as WISE 1534–1043, nicknamed “The Accident.” Early spectra from these objects reveal cloud structures and chemical abundances that ground-based telescopes could not resolve. The observations supply direct atmospheric benchmarks that theorists can use to model how the coldest brown dwarfs retain heat and whether similar conditions could appear on free-floating exoplanets.

Binary Systems and Companions Among Ultracool Dwarfs

Recent catalogs show that many ultracool dwarfs travel with stellar companions. 2024 studies added 89 new ultracool companions to FGK stars, a 42 percent increase over prior counts. Additional systems pair M-dwarfs with T-dwarfs or place ultracool objects in wide orbits around white dwarfs, some extending thousands of astronomical units. Citizen scientists flagged several of these co-moving pairs, demonstrating that the neighborhood map grows more crowded the longer volunteers keep looking.

Citizen Scientists as Co-Authors and Career Pathways

The 2026 paper is not an outlier. Volunteers have built custom search scripts that later appeared in professional analyses, and several have presented at conferences alongside staff astronomers. The project’s longevity has turned a one-time outreach experiment into a pipeline that feeds both new discoveries and new researchers into the field.

The grey-alien angle remains speculative, yet the data keep shrinking the distance between Earth and the nearest potentially habitable-temperature worlds. Each new brown dwarf adds a data point, and each volunteer click moves the catalog forward. After ten years the experiment shows no sign of winding down.