juliensimon/galaxy-zoo-2-morphology
Galaxy Zoo 2 Morphological Classifications Part of the Astronomy Datasets collection on Hugging Face. 243,500 citizen-science galaxy morphology classifications from Galaxy Zoo 2, the largest visual morphological classification project in astronomy. Each galaxy was classified by multiple volunteers answering a decision tree of questions about shape, structure, and features. Dataset description Galaxy Zoo 2 asked hundreds of thousands of volunteers to classify… See the full description on the dataset page: https://huggingface.co/datasets/juliensimon/galaxy-zoo-2-morphology.
Galaxy Zoo 2 Morphological Classifications
Part of the [Astronomy Datasets](https://huggingface.co/collections/juliensimon/astronomy-datasets-69c24caf2f17e36128946743) collection on Hugging Face.
243,500 citizen-science galaxy morphology classifications from Galaxy Zoo 2, the largest visual morphological classification project in astronomy. Each galaxy was classified by multiple volunteers answering a decision tree of questions about shape, structure, and features.
Dataset description
Galaxy Zoo 2 asked hundreds of thousands of volunteers to classify galaxy images from the Sloan Digital Sky Survey (SDSS). This dataset contains the spectroscopic-redshift sample (Table 5 from Willett et al. 2013): 243,500 galaxies with vote counts, vote fractions, weighted fractions, debiased probabilities, and classification flags for 11 morphological tasks spanning 37 possible answers.
The decision tree covers: smooth vs. featured, edge-on disk, bar presence, spiral structure, bulge prominence, oddities (ring, lens, disturbed, irregular, merger, dust lane), roundedness, bulge shape, and spiral arm properties (tightness, count).
Quick stats
- 243,500 galaxies classified
- 103,515 classified as smooth/elliptical
- 139,738 classified as featured/disk
- 86,775 with spiral structure (debiased probability > 0.5)
- 34,286 barred galaxies (debiased probability > 0.5)
- 29,597 edge-on galaxies (debiased probability > 0.5)
- 179.4 average votes per galaxy
Schema
The dataset has 237 columns. Key columns:
For each of the 11 morphological tasks (t01-t11) and their answers (a01-a37), there are up to 6 columns:
Usage
from datasets import load_dataset
ds = load_dataset("juliensimon/galaxy-zoo-2-morphology", split="train")
df = ds.to_pandas()
# Elliptical galaxies (smooth, debiased probability > 0.8)
ellipticals = df[df["t01_smooth_or_features_a01_smooth_debiased"] > 0.8]
# Barred spiral galaxies
barred_spirals = df[df["is_barred"] & df["is_spiral"]]
# Edge-on disks
edge_on = df[df["is_edge_on"]]
# Distribution of morphological classes
print(df["gz2class"].value_counts().head(10))
# Merger candidates (odd feature = merger, debiased > 0.5)
if "t08_odd_feature_a24_merger_debiased" in df.columns:
mergers = df[df["t08_odd_feature_a24_merger_debiased"] > 0.5]Data source
Galaxy Zoo 2 — Willett et al. (2013), "Galaxy Zoo 2: detailed morphological classifications for 304,122 galaxies from the Sloan Digital Sky Survey", MNRAS, 435, 2835. arXiv:1308.3496
This table is the spectroscopic-redshift subsample (Table 5).
Related datasets
- open-ngc — NGC/IC galaxy and nebula catalog
- exoplanets — NASA Exoplanet Archive
- messier-objects — Messier catalog of deep-sky objects
Pipeline
Source code: juliensimon/space-datasets
Citation
@dataset{galaxy_zoo_2_morphology,
author = {Simon, Julien},
title = {Galaxy Zoo 2 Morphological Classifications},
year = {2026},
publisher = {Hugging Face},
url = {https://huggingface.co/datasets/juliensimon/galaxy-zoo-2-morphology},
note = {Based on Galaxy Zoo 2 data (Willett et al. 2013, MNRAS 435, 2835)}
}