---
title: "RX J1131-1231"
url: "https://spacecatalog.org/object/rx-j1131-1231"
release: "DR1"
licence: "CC-BY-4.0"
citation: "SpaceCatalog. RX J1131-1231 [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/rx-j1131-1231"
---

# RX J1131-1231

RX J1131-1231 is a quasar in the constellation [Crater](https://spacecatalog.org/constellation/crater), 12.71 Gly from Earth. It was discovered in 2003.

A lensed quasar whose X-ray spectrum gave the first spin measurement for a [black hole](https://spacecatalog.org/black-holes) this far away: it turns at about half the speed of light. Spin is a record of how the hole was fed, so measuring it anywhere but nearby is a statement about the history of the whole population.

## At a glance

- **WHAT IT IS:** Quasar
- **HOW FAR:** 12.71 Gly — A luminosity distance, from its redshift — how faint it looks. The light itself left 6.00 billion years ago.
- **WHERE TO LOOK:** [Crater](https://spacecatalog.org/constellation/crater) — The patch of sky it sits in, as seen from Earth.

## Properties

| Quantity | Value |
| --- | --- |
| CLASS | Quasar |
| DISTANCE FROM EARTH | 12.71 Gly — by luminosity distance from a published redshift, flat ΛCDM with H0 = 70 km/s/Mpc |
| CONSTELLATION | Crater |
| RIGHT ASCENSION (J2000) | 11h 31m 51.5s |
| DECLINATION (J2000) | −12° 31′ 58.7″ |
| DISCOVERED | 2003 |

## Catalogue data

### WHAT KIND OF THING IT IS

What the object is in itself, rather than how it happens to look from here.

| Field | Value |
| --- | --- |
| Accretion state | quasar — a thin disc near its Eddington limit |

### WHERE IT IS AND HOW IT MOVES

Position, motion across the sky and the size it covers on it. These are measurements of the object as seen from here, so every one of them depends on where here is.

| Field | Value |
| --- | --- |
| Redshift (z) | 0.65427467 |

## Also known as

- Common name: RX J1131-1231

## Source

[SpaceCatalog curated data](https://spacecatalog.org/releases) — CC-BY-4.0

How this was made: https://spacecatalog.org/methods#source-curated

## Cite this page

SpaceCatalog. RX J1131-1231 \[catalogue entry\]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/rx-j1131-1231

```bibtex
@misc{spacecatalog_rx-j1131-1231,
  author       = {{SpaceCatalog}},
  title        = {{RX J1131-1231}},
  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
  year         = {2026},
  url          = {https://spacecatalog.org/object/rx-j1131-1231},
  note         = {Catalogue entry, data release DR1 (2026-08-21). Values from SpaceCatalog curated data.}
}
```

SpaceCatalog curated data — CC-BY-4.0

The page itself, with its pictures, the sky map and the observing tools: https://spacecatalog.org/object/rx-j1131-1231