Datasets:
license: cc-by-4.0
pretty_name: ICRF3 Celestial Reference Frame
language:
- en
description: >-
The third International Celestial Reference Frame (ICRF3) — the fundamental
coordinate reference frame for astronomy, defined by extragalactic radio
sources observed by VLBI.
task_categories:
- tabular-classification
tags:
- space
- icrf
- reference-frame
- astrometry
- quasar
- vlbi
- open-data
size_categories:
- 1K<n<10K
ICRF3 Celestial Reference Frame
The third International Celestial Reference Frame (ICRF3) is the fundamental coordinate reference frame for astronomy, adopted by the International Astronomical Union in 2018. It is defined by 4,588 extragalactic radio sources (primarily quasars) observed by Very Long Baseline Interferometry (VLBI). This dataset contains 3,417 sources with variability and structure parameters from the defining catalog.
Dataset description
The ICRF is the realization of the International Celestial Reference System (ICRS) at radio wavelengths. ICRF3 is based on nearly 40 years of VLBI observations and provides the most accurate positions of extragalactic objects, with median positional uncertainties of ~30 microarcseconds for the defining sources. These sources serve as the fixed reference points against which all other celestial positions are measured.
Schema
| Column | Type | Description |
|---|---|---|
iers_name |
string | IERS designation of the source |
ra_deg |
float64 | Right ascension (degrees, ICRS) |
dec_deg |
float64 | Declination (degrees, ICRS) |
Additional columns from the catalog are included with snake_case names.
Quick stats
- 3,417 ICRF3 sources
Usage
from datasets import load_dataset
ds = load_dataset("juliensimon/icrf3-reference-frame", split="train")
df = ds.to_pandas()
# All-sky distribution
print(f"{len(df):,} ICRF3 reference sources")
print(f"RA range: {df['ra_deg'].min():.2f} to {df['ra_deg'].max():.2f} deg")
print(f"Dec range: {df['dec_deg'].min():.2f} to {df['dec_deg'].max():.2f} deg")
Data source
Xu, M.H., Anderson, J.M., Heinkelmann, R., et al. (2019), "Structure Effects for 3417 Celestial Reference Frame Radio Sources", ApJS, 242, 5. Accessed via VizieR, CDS Strasbourg.
Related datasets
- pulsar-catalog -- ATNF Pulsar Catalogue
- open-star-clusters -- Open Star Clusters
Pipeline
Source code: juliensimon/space-datasets
Citation
@dataset{icrf3_reference_frame,
author = {Simon, Julien},
title = {ICRF3 Celestial Reference Frame},
year = {2026},
publisher = {Hugging Face},
url = {https://huggingface.co/datasets/juliensimon/icrf3-reference-frame},
note = {Based on Xu et al. (2019), ApJS, 242, 5 via VizieR CDS Strasbourg}
}