---
title: "Kepler-81 d"
url: "https://spacecatalog.org/object/kepler-81-d"
release: "DR1"
licence: "No licence stated; acknowledgement requested"
citation: "SpaceCatalog. Kepler-81 d [catalogue entry]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/kepler-81-d"
---

# Kepler-81 d

Kepler-81 d is a terrestrial [planet](https://spacecatalog.org/planets) in the constellation [Cygnus](https://spacecatalog.org/constellation/cygnus), 1136 ly from Earth. It orbits Kepler-81 at a mean distance of 0.128 AU. It has a mass of 1.92 M⊕ and a radius of 1.21 R⊕ · 7718 km. It was discovered in 2014.

## At a glance

- **WHAT IT IS:** Terrestrial planet
- **HOW FAR:** 1136 ly — The light arriving now left it that long ago.
- **HOW BIG:** 1.21 R⊕ · 7718 km — Its radius: half the width across.
- **WHERE TO LOOK:** [Cygnus](https://spacecatalog.org/constellation/cygnus) — The patch of sky it sits in, as seen from Earth.
- **ONE ORBIT TAKES:** 20.8 days — One trip round Kepler-81.

## Properties

| Quantity | Value |
| --- | --- |
| CLASS | Terrestrial planet |
| MASS | 1.92 M⊕ |
| RADIUS | 1.21 R⊕ · 7718 km ±1722 |
| DISTANCE FROM EARTH | 1136 ly ±10 — by NASA Exoplanet Archive sy\_dist (TICv8, 2019AJ....158..138S) |
| ORBITS | Kepler-81 |
| SEMI-MAJOR AXIS | 0.128 AU |
| CONSTELLATION | Cygnus |
| RIGHT ASCENSION (J2000) | 19h 34m 32.9s |
| DECLINATION (J2000) | +42° 49′ 29.4″ |
| DISCOVERED | 2014 |

## 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 | 418 K |
| Host star spectral type | M0 V |
| Host star temperature | 4500 ±116 K |
| Host star mass | 0.648 ±0.028 M☉ |
| Host star radius | 0.595 ±0.029 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) | 15.26 |

### 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 | Kepler-81 |
| Orbital period | 20.837846 days ±0.00018 |
| Eccentricity | 0 |
| Inclination | 89.18° |
| Transit midpoint | 2454965.0796 BJD |
| Stars in system | 1 |
| Planets in system | 3 |

### WHEN IT WAS FOUND

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

| Field | Value |
| --- | --- |
| Discovery method | Transit |
| Discovered at | Kepler |

## Also known as

- Exoplanet: Kepler-81 d
- Host star: Kepler-81

## 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. Kepler-81 d \[catalogue entry\]. Data release DR1 (2026-08-21). https://spacecatalog.org/object/kepler-81-d

```bibtex
@misc{spacecatalog_kepler-81-d,
  author       = {{SpaceCatalog}},
  title        = {{Kepler-81 d}},
  howpublished = {SpaceCatalog, data release DR1 (2026-08-21)},
  year         = {2026},
  url          = {https://spacecatalog.org/object/kepler-81-d},
  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/kepler-81-d