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). 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):
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. 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. Only the MPC observations are public.
Questions are welcome in this thread!
— Mario Jurić and Matthew Holman, for the Rubin Solar System team
