Update Pantheon+ SNe Ia: 1,701 supernovae

README.md

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+---
+license: cc-by-4.0
+pretty_name: "Pantheon+ Type Ia Supernovae"
+language:
+  - en
+description: "Gold standard cosmological dataset: 1,701 spectroscopically confirmed Type Ia supernovae from Pantheon+ used to measure H0 and dark energy."
+task_categories:
+  - tabular-regression
+tags:
+  - space
+  - supernova
+  - cosmology
+  - hubble-constant
+  - dark-energy
+  - pantheon
+  - open-data
+size_categories:
+  - 1K<n<10K
+---
+
+# Pantheon+ Type Ia Supernovae
+
+The gold standard cosmological dataset -- **1,701** spectroscopically confirmed Type Ia supernovae
+from the Pantheon+ analysis, used to measure the Hubble constant (H0) and constrain the dark energy
+equation of state. This is the dataset behind the "Hubble tension" debate.
+
+## Dataset description
+
+Pantheon+ combines supernova light curves from 20 surveys spanning redshifts
+0.0012 to 2.261. Each SN Ia is standardized using the SALT2 light-curve fitter,
+providing stretch (x1) and color (c) parameters that transform raw apparent magnitudes into
+calibrated distance moduli. Combined with Cepheid-calibrated distances from SH0ES, this
+dataset yields the most precise local measurement of the Hubble constant.
+
+## Schema
+
+| Column | Type | Description |
+|--------|------|-------------|
+| `sn_name` | string | Supernova identifier (CID) |
+| `survey_id` | int64 | Survey identifier |
+| `redshift_hd` | float64 | Hubble-diagram redshift (peculiar velocity corrected) |
+| `redshift_hd_err` | float64 | Hubble-diagram redshift uncertainty |
+| `redshift_cmb` | float64 | CMB-frame redshift |
+| `redshift_cmb_err` | float64 | CMB-frame redshift uncertainty |
+| `redshift_helio` | float64 | Heliocentric redshift |
+| `redshift_helio_err` | float64 | Heliocentric redshift uncertainty |
+| `apparent_mag_b` | float64 | Apparent B-band magnitude (SALT2 mB) |
+| `apparent_mag_b_err` | float64 | Apparent magnitude uncertainty |
+| `stretch_x1` | float64 | SALT2 stretch parameter x1 |
+| `stretch_x1_err` | float64 | Stretch uncertainty |
+| `color_c` | float64 | SALT2 color parameter c |
+| `color_c_err` | float64 | Color uncertainty |
+| `host_log_mass` | float64 | Host galaxy log stellar mass (solar masses) |
+| `host_log_mass_err` | float64 | Host mass uncertainty |
+| `fit_probability` | float64 | SALT2 fit probability |
+| `distance_modulus` | float64 | Distance modulus from SH0ES analysis |
+| `distance_modulus_err` | float64 | Distance modulus diagonal uncertainty |
+
+## Quick stats
+
+- **1,701** Type Ia supernovae from **20** surveys
+- Redshift range: 0.0012 to 2.261 (median 0.164)
+- Distance modulus range: 29.00 to 46.18 mag
+
+## Usage
+
+```python
+from datasets import load_dataset
+
+ds = load_dataset("juliensimon/pantheon-plus-sne-ia", split="train")
+df = ds.to_pandas()
+
+# Hubble diagram
+import matplotlib.pyplot as plt
+import numpy as np
+
+valid = df[df["distance_modulus"] > 0]
+plt.errorbar(valid["redshift_cmb"], valid["distance_modulus"],
+             yerr=valid["distance_modulus_err"],
+             fmt=".", ms=2, alpha=0.5, elinewidth=0.5)
+plt.xscale("log")
+plt.xlabel("Redshift (CMB frame)")
+plt.ylabel("Distance modulus (mag)")
+plt.title("Pantheon+ Hubble Diagram")
+plt.show()
+
+# Color-stretch distribution
+plt.scatter(df["stretch_x1"], df["color_c"], s=2, alpha=0.3)
+plt.xlabel("Stretch x1")
+plt.ylabel("Color c")
+plt.title("SALT2 Parameter Distribution")
+plt.show()
+
+# Redshift distribution
+df["redshift_cmb"].hist(bins=50)
+plt.xlabel("Redshift")
+plt.ylabel("Count")
+plt.title("Pantheon+ Redshift Distribution")
+plt.show()
+```
+
+## Data source
+
+Scolnic, D., et al. (2022), *The Pantheon+ Analysis: The Full Dataset and Light-curve Release.*
+Astrophysical Journal, 938, 113.
+
+Brout, D., et al. (2022), *The Pantheon+ Analysis: Cosmological Constraints.*
+Astrophysical Journal, 938, 110.
+
+Data release: [PantheonPlusSH0ES/DataRelease](https://github.com/PantheonPlusSH0ES/DataRelease)
+
+## Pipeline
+
+Source code: [juliensimon/space-datasets](https://github.com/juliensimon/space-datasets)
+
+## Citation
+
+```bibtex
+@dataset{pantheon_plus_sne,
+  author = {Simon, Julien},
+  title = {Pantheon+ Type Ia Supernovae},
+  year = {2026},
+  publisher = {Hugging Face},
+  url = {https://huggingface.co/datasets/juliensimon/pantheon-plus-sne-ia},
+  note = {Based on Scolnic et al. (2022) and Brout et al. (2022) Pantheon+ data release}
+}
+```
+
+## License
+
+[CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/)

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