juliensimon/gravitational-lenses

---
license: cc-by-4.0
pretty_name: "Strong Gravitational Lens Catalog"
language:
- en
description: "32,838 strong gravitational lenses from the lenscat catalog, including galaxies and galaxy clusters with coordinates, redshifts, and confidence gradings."
task_categories:
- tabular-classification
tags:
- space
- gravitational-lensing
- astronomy
- cosmology
- open-data
- tabular-data
size_categories:
- 10K<n<100K
configs:
- config_name: default
data_files:
- split: train
path: data/gravitational_lenses.parquet
default: true
---

# Strong Gravitational Lens Catalog

*Part of the [Astronomy Datasets](https://huggingface.co/collections/juliensimon/astronomy-datasets-69c24caf2f17e36128946743) collection on Hugging Face.*

A comprehensive catalog of **32,838** confirmed and probable strong gravitational lenses
compiled by the [lenscat](https://github.com/lenscat/lenscat) project. Covers both galaxy-scale
and cluster-scale lenses drawn from dozens of surveys and publications.

## Dataset description

Strong gravitational lensing occurs when a massive foreground object (a galaxy or galaxy cluster)
bends the light of a background source so severely that multiple images, arcs, or Einstein rings
are produced. This catalog consolidates discoveries from major surveys including SDSS, DES,
HSC, CLASH, RELICS, and many others into a single machine-readable table.

Each entry records the lens name, sky coordinates, lens redshift (when measured), morphological
type (galaxy or cluster), a confidence grading, and a literature reference.

## Schema

| Column | Type | Description |
|--------|------|-------------|
| `name` | string | Lens system name / identifier |
| `ra_deg` | float64 | Right ascension (J2000, degrees) |
| `dec_deg` | float64 | Declination (J2000, degrees) |
| `lens_redshift` | float64 | Spectroscopic redshift of the lens (null if unmeasured) |
| `lens_type` | string | Morphological type: "galaxy" or "cluster" |
| `grading` | string | Confidence level: "confident" or "probable" |
| `reference` | string | Discovery / catalog reference (URL or bibcode) |

## Quick stats

- **32,838** strong gravitational lenses
- **31,755** galaxy-scale lenses, **1,023** cluster-scale lenses
- **2,309** confident, **30,529** probable
- **13,974** lenses with measured redshifts (range 0.000 -- 3.000, median 0.480)

## Usage

```python
from datasets import load_dataset

ds = load_dataset("juliensimon/gravitational-lenses", split="train")
df = ds.to_pandas()

# Sky distribution
import matplotlib.pyplot as plt
plt.scatter(df["ra_deg"], df["dec_deg"], s=0.2, alpha=0.3)
plt.xlabel("RA (deg)")
plt.ylabel("Dec (deg)")
plt.title("Strong Gravitational Lenses -- Sky Distribution")
plt.gca().invert_xaxis()
plt.show()

# Redshift distribution
df["lens_redshift"].dropna().hist(bins=60)
plt.xlabel("Lens Redshift")
plt.ylabel("Count")
plt.title("Lens Redshift Distribution")
plt.show()

# Galaxy vs cluster breakdown
df["lens_type"].value_counts().plot.bar()
plt.title("Lens Type Distribution")
plt.show()

# Confident vs probable by type
df.groupby(["lens_type", "grading"]).size().unstack().plot.bar()
plt.title("Grading by Lens Type")
plt.show()
```

## Data source

Compiled by the [lenscat](https://github.com/lenscat/lenscat) project, which consolidates
strong lens discoveries from the literature into a single catalog. See the project repository
for the full list of contributing surveys and references.

## Pipeline

Source code: [juliensimon/space-datasets](https://github.com/juliensimon/space-datasets)

## Citation

```bibtex
@dataset{gravitational_lenses,
author = {Simon, Julien},
title = {Strong Gravitational Lens Catalog},
year = {2026},
publisher = {Hugging Face},
url = {https://huggingface.co/datasets/juliensimon/gravitational-lenses},
note = {Based on the lenscat project (https://github.com/lenscat/lenscat)}
}
```

## License

[CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/)