A small-telescope survey of variable stars — stars that pulse, erupt, and eclipse, and the exoplanets that cross them — built on an open pipeline that measures thousands at once against the AAVSO VSX × Gaia catalog. Every line of code, every observing plan, and every report here is developed in collaboration with Anthropic's Claude Code, making the project a working showcase of what AI can do in a real scientific domain.
The Science
The whole variable sky — all 10.3 million stars in the AAVSO Variable Star Index, in galactic coordinates. The Milky Way's plane glows across the middle, the Magellanic Clouds hang below at right, and the faint loops trace how surveys like Gaia have swept the heavens. Explore it interactively →
Most stars look fixed, but a huge fraction are variable: their brightness changes over hours, days, or years. Those changes are a direct window into stellar physics — the pulsation of dying giants, the tug of orbiting companions, the runaway fusion of a nova. Long-baseline monitoring of these stars underpins the cosmic distance ladder and the whole field of time-domain astronomy.
The Variable Zoo focuses on the objects a backyard telescope can follow well — especially long-period variables and eruptive systems — turning ordinary deep-sky imaging into quantitative, catalogued measurements.
A short history of variable-star astronomy → — from the first observers who proved the sky was not eternal to what one person can measure today.
On the evening of 9 July 2026, a small refractor no wider than a coffee mug pointed at an unremarkable speck in the constellation Cygnus and started taking pictures, one every half-minute, for six hours. The speck is called SS Cygni, and it is one of the most famous variable stars in the sky. I expected to catch it dozing. Instead, I caught it erupting.
The real thing — SS Cygni across a single 6.4-hour night. Every teal point is one 30-second frame our pipeline measured and anchored to Gaia G; the coral curve traces a slow ~0.17-mag modulation riding on the fast flicker of its accretion disk. This is exactly the kind of measurement the Variable Zoo turns ordinary deep-sky imaging into. Read the story →
Source: The Variable Zoo Project
Stellar Diversity
Every family keeps its own hours. Here are the periods of 1.87 million catalogued variables, split by type — from the minutes-long pulsations of white dwarfs at left to the thousand-day breaths of Mira giants at right. The sharp edges are physics: the 0.22-day floor of contact binaries, the narrow RR Lyrae strip set by the horizontal branch. Colour marks the mechanism — teal pulsating, blue eclipsing, green rotating.
The Menagerie
Stars vary for many reasons — pulsation, eclipses, starspots, cataclysmic outbursts. Each leaves a distinctive light-curve signature. These are the "animals" of the Variable Zoo; our survey aims to measure and monitor them across wide fields of the sky. Learn more about variable-star taxonomy →
Cool red giants that swing many magnitudes over months to years.
Learn more →Old, metal-poor pulsators — the sawtooth heartbeat of the Galactic halo.
Learn more →Their pulsation period tracks luminosity, anchoring the distance ladder.
Learn more →Rapid, low-amplitude pulsations near the main-sequence turnoff.
Learn more →Two stars, one orbit: sharp dips as each passes in front of the other.
Learn more →Stars so close they share an envelope, in continuous ever-changing light.
Learn more →A white dwarf feeding off a companion, flaring in sudden outbursts.
Learn more →Dark spots carried in and out of view as the star turns.
Learn more →A planet crossing its star's face dims it a percent or two — the same photometry catches these.
Learn more →Method
Small astrophotography rigs at Lowell Observatory, an open photometry pipeline, and a half-billion-star reference catalog.
A 60 mm refractor and a 17-inch PlaneWave record thousands of stars per frame, each field plate-solved against Gaia DR3.
Every source is matched to the AAVSO VSX catalog and measured differentially, anchored to Gaia G — no per-star calibration needed.
Measurements fold onto catalog ephemerides and accumulate into a growing database of observations across many variability classes.
Results
SS Cyg
SS Cyg
DY Her
Lacerta Exposure-Ramp Experiment
Data
Three ways into the data — an all-sky map of the reference catalog, our own survey measurements, and a full catalog search — each running right in your browser.
Map all 10.3 million catalogued variables across the sky — by category, subtype, and physical parameters, with density colormaps.
Browse Variable Zoo's own measurements — light curves and phase‑folds across many nights and targets.
Search 10.3 million variable stars (VSX × Gaia) by name, position, type, magnitude, and period — with full detail pages.
The Showcase
The Variable Zoo is, deliberately, a demonstration of AI-driven scientific research. The photometry pipeline, the plate-solving, the analysis, the observing plans, and the reports on this site were all developed in a sustained collaboration with Anthropic's Claude Code. We are up-front about this because we think it is the point: a working example of what human–AI partnership can accomplish in a real scientific domain.
Sets the scientific direction and the questions that matter, runs the telescopes, provides domain judgment, and decides what is real and what is worth pursuing.
Writes and debugs the pipeline, derives astrometry and photometry, runs the analysis, drafts the plans and reports, and builds this site — under continuous human review.
About
The Variable Zoo Project is led by Dr. John Rachlin, Associate Teaching Professor at the Khoury College of Computer Sciences, Northeastern University, and an avid astrophotographer who volunteers as a telescope operator at Lowell Observatory's Giovale Open Deck Observatory in Flagstaff, Arizona. Reach him at [email protected].