# 2026 ED138: a dwarf-planet candidate found in early Rubin data, and its data on the RSP

**URL:** <https://www.rubin.community/t/2026-ed138-a-dwarf-planet-candidate-found-in-early-rubin-data-and-its-data-on-the-rsp/12877>\
**Category:** News\
**Tags:** solarsystem\
**Created:** [October 27, 2026, 6:35pm UTC](https://www.rubin.community/t/2026-ed138-a-dwarf-planet-candidate-found-in-early-rubin-data-and-its-data-on-the-rsp/12877 "2026-10-27T18:35:03Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mjuric](https://sea2.discourse-cdn.com/flex002/user_avatar/www.rubin.community/mjuric/32/31_2.png) [@mjuric](https://www.rubin.community/u/mjuric)\
**Post date:** [October 27, 2026, 6:35pm UTC](https://www.rubin.community/t/2026-ed138-a-dwarf-planet-candidate-found-in-early-rubin-data-and-its-data-on-the-rsp/12877/1 "2026-10-27T18:35:03Z")

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Today the Minor Planet Center announced **2026 ED138** , a large trans-Neptunian object found in Rubin LSSTCam data taken in the run-up to the LSST ([MPEC 2026-U85](https://www.minorplanetcenter.net/mpec/K26/K26U85.html)). Matthew Holman, Rubin Solar System Operations team member, found it in the lastest run of his distant-object search pipelines in Rubin’s single-visit source catalogs.

**The object**

| | |
| --- | --- |
| Absolute magnitude | H\_V = 3.19 ± 0.04. Only 9 known TNOs are intrinsically brighter. It is the brightest TNO found since (532037) Chiminigagua in 2013. |
| Size | about 610–1,530 km for geometric albedos 0.25–0.04 (about 970 km at 0.10), which makes it a dwarf-planet candidate pending an albedo or occultation measurement |
| Orbit (barycentric) | a = 43.09 au, e = 0.139, i = 24.4°, q = 37.1 au |
| Dynamics | near the 12:7 mean-motion resonance with Neptune (like Haumea); about half of the orbits consistent with the data librate, so its resonant membership is not yet settled |
| Color | g − r = 0.63: redder than the Haumea family, so not a family member |
| Brightness | i ≈ 19.4, at Dec ≈ −43° and Galactic latitude ≈ −12°: bright enough for ground-based spectroscopy and lightcurves |
| Arc | 30 Rubin observations on 20 nights (2026 March 4 – July 11) and DECam precoveries on 14 nights (2016–2023): more than 10 years in all |

The low Galactic latitude is why earlier surveys missed it: they avoided this crowded part of the sky or covered it only shallowly. The Rubin observations and DECam precoveries are at the MPC.

**Data on the Rubin Science Platform**

For Rubin data rights holders, the Rubin data for 2026 ED138 are on the RSP (data.lsst.cloud) at:

```
/rubin/shared/datasets/2026-ED138

```

It holds:

- every LSSTCam image the object falls on (calibrated single-visit images and raws), plus images of the same sky on other nights;
- single-visit source catalogs around the track, from Daytime Alert Production, Prompt Processing and nightly validation;
- visit metadata (ConsDB and SSP visit tables);
- the 30 observations submitted to the MPC (`ades/2026_ED138.psv`).

All 1,428 datasets in 63 runs (24 GB) are in a ready-made, read-only Butler repository, so no import is needed (LSST Science Pipelines w\_2026\_41 or later; the RSP default works):

```python
from lsst.daf.butler import Butler
butler = Butler("/rubin/shared/datasets/2026-ED138/butler_repo", collections="2026-ED138")
refs = butler.query_datasets("preliminary_visit_image",
                             where="instrument = 'LSSTCam' AND visit = 2026030300796")
image = butler.get(refs[0])

```

The metadata are Parquet tables in `metadata/`, with SQL schemas. `README.md` in the directory describes the contents and use. A `butler_export/` is also included, for importing into your own repository.

**These are proprietary data, for Rubin data rights holders only** , under the [Rubin Data Policy](https://rubinobservatory.org/for-scientists/data-products/data-policy). Please read `DATA-RIGHTS.md` in the directory before using them. Publications that use these data must meet the policy’s co-authorship requirements for proprietary data. They must also include the proprietary-data acknowledgement and Rubin’s funding acknowledgement (and the RSP acknowledgement if you worked on the RSP), all from [Acknowledgements — Citations](https://citations.lsst.io/acknowledgements/). Only the MPC observations are public.

Questions are welcome in this thread!

— Mario Jurić and Matthew Holman, for the Rubin Solar System team

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<div class="post-metadata">

**Author:** ![mjuric](https://sea2.discourse-cdn.com/flex002/user_avatar/www.rubin.community/mjuric/32/31_2.png) [@mjuric](https://www.rubin.community/u/mjuric)\
**Post date:** [October 27, 2026, 7:00pm UTC](https://www.rubin.community/t/2026-ed138-a-dwarf-planet-candidate-found-in-early-rubin-data-and-its-data-on-the-rsp/12877/2 "2026-10-27T19:00:55Z")

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Here is the Rubin press release with some nice figures, videos and visualizations: [NSF–DOE Vera C. Rubin Observatory Reveals Its First Dwarf Planet Candidate in Our Solar System | Rubin Observatory](https://rubinobservatory.org/news/rubin-first-dwarf-planet-candidate)