---
title: "GJ 229 A c"
url: "https://spacecatalog.org/object/gj-229-a-c"
release: "DR1"
licence: "No licence stated; acknowledgement requested"
citation: "SpaceCatalog. GJ 229 A c [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/gj-229-a-c"
---

# GJ 229 A c

GJ 229 A c is a Neptune-like [planet](https://spacecatalog.org/planets) in the constellation [Lepus](https://spacecatalog.org/constellation/lepus), 18.77 ly from Earth. It orbits GJ 229 at a mean distance of 0.384 AU. It has a mass of 8.58 M⊕ and a radius of 2.87 R⊕ · 18 305 km. It was discovered in 2020.

## At a glance

- **WHAT IT IS:** Neptune-like planet
- **HOW FAR:** 18.77 ly — The light arriving now left it that long ago.
- **HOW BIG:** 2.87 R⊕ · 18 305 km — Its radius: half the width across.
- **WHERE TO LOOK:** [Lepus](https://spacecatalog.org/constellation/lepus) — The patch of sky it sits in, as seen from Earth.
- **ONE ORBIT TAKES:** 122 days — One trip round GJ 229.

## Properties

| Quantity | Value |
| --- | --- |
| CLASS | Neptune-like planet |
| MASS | 8.58 M⊕ ±0.64 |
| RADIUS | 2.87 R⊕ · 18 305 km |
| DISTANCE FROM EARTH | 18.77 ly — by NASA Exoplanet Archive sy\_dist (TICv8, 2019AJ....158..138S) |
| ORBITS | GJ 229 |
| SEMI-MAJOR AXIS | 0.384 AU ±0.005 |
| CONSTELLATION | Lepus |
| RIGHT ASCENSION (J2000) | 06h 10m 34.5s |
| DECLINATION (J2000) | −21° 52′ 03.8″ |
| DISCOVERED | 2020 |

## 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 |
| --- | --- |
| Equilibrium temperature | 188.1 K |
| Host star spectral type | M1.5V |
| Host star temperature | 3564 K |
| Host star mass | 0.509 ±0.02 M☉ |
| Host star radius | 0.46 +0.01 / −0.02 R☉ |

### HOW BRIGHT IT IS

What the light adds up to, measured through one filter at a time. A magnitude is a brightness on a backwards scale — the smaller the number, the brighter the object.

| Field | Value |
| --- | --- |
| Host star apparent magnitude (V) | 8.15 |

### THE ORBIT

The shape of the path, where the object sits on it, and the instant those figures were true of. An orbit is a fit to observations and drifts away from the real one either side of its epoch.

| Field | Value |
| --- | --- |
| Host star | GJ 229 |
| Orbital period | 121.93268 days +0.067 / −0.082 |
| Eccentricity | 0.366 +0.065 / −0.063 |
| Argument of periastron | 128.62 +9.2 / −9.4° |
| Periastron epoch | 2450370.1800 BJD |
| Stars in system | 3 |
| Planets in system | 2 |

### WHEN IT WAS FOUND

Who first saw it, from where, and by what method.

| Field | Value |
| --- | --- |
| Discovery method | Radial Velocity |
| Discovered at | Multiple Facilities |

## Also known as

- Exoplanet: GJ 229 A c
- Host star: GJ 229

## Source

[NASA Exoplanet Archive (Planetary Systems Composite Parameters)](https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=PSCompPars) — No licence stated; acknowledgement requested

The producer asks: This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Cite Christiansen et al. (2025), Planetary Science Journal (doi:10.3847/PSJ/ade3c2), and the literature reference given with each value.

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

## Cite this page

SpaceCatalog. GJ 229 A c \[catalogue entry\]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/gj-229-a-c

```bibtex
@misc{spacecatalog_gj-229-a-c,
  author       = {{SpaceCatalog}},
  title        = {{GJ 229 A c}},
  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
  year         = {2026},
  url          = {https://spacecatalog.org/object/gj-229-a-c},
  note         = {Catalogue entry, data release DR1 (2026-08-21). Values from NASA Exoplanet Archive (Planetary Systems Composite Parameters).}
}
```

NASA Exoplanet Archive (Planetary Systems Composite Parameters) — No licence stated; acknowledgement requested

Acknowledgement the producer asks for: This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Cite Christiansen et al. (2025), Planetary Science Journal (doi:10.3847/PSJ/ade3c2), and the literature reference given with each value.

The page itself, with its pictures, the sky map and the observing tools: https://spacecatalog.org/object/gj-229-a-c