Check out these earlier threads for more info on the venerable Vera C. Rubin Observatory, located on Cerro Pachón in Chile, with its 3.2 gigapixel wide-angle camera.
The observatory is named after astronomer Vera Rubin, who provided the first convincing evidence for the existence of dark matter.
https://fosstodon.org/@AkaSci/114150485502312076
https://fosstodon.org/@AkaSci/114731082323927544
4/n
The amazing Vera C. Rubin Observatory.
In April, even before observations formally began, the Rubin Solar System team submitted observations of over 11,000 new asteroids, which included ~380 new trans-Neptunian objects (TNOs).
What other celestial wonders will it discover and what astronomical mysteries will it solve?
Randall Munroe had some ideas 😄
https://fosstodon.org/@AkaSci/117006287296978668
5/n
This is how newly discovered dwarf planet candidate 2026 ED138 stacks up against other well-known trans-Neptunian dwarf planets.
It seems similar to Haumea and Makemake in orbit and size, perhaps a bit smaller.
Data sources:
https://en.wikipedia.org/wiki/Dwarf_planet
https://www.minorplanetcenter.net/db_search/show_object?object_id=2026+ED138
6/n
Dwarf Planet candidate ED138 was not discovered until now because it currently lies in a region of the sky close to the plane of the Milky Way — a region filled with millions of stars.
The video below shows the orbital path of ED138, as observed by the NSF–DOE Vera C. Rubin Observatory from 4 March 2026 to 11 July 2026, against a background filled with stars.
The angular distance traveled in the 4 months is quite small, ~1°, given its orbital period of 281 years.
Here is the approx. location of dwarf planet candidate 2026 ED138 as seen in the evening sky from Cerro Pachón, Chile, home to the Vera C. Rubin Observatory.
It is quite close to the plane of the Milky Way, which is teeming with stars.
Note that Kaus Australis is 143 light years away, while ED138, at 46 au, is just 0.0007 light years (0.26 light days) from Earth.
For more detailed co-ordinates, see https://www.minorplanetcenter.net/db_search/show_object?object_id=2026+ED138
8/n
Oct 28, 2026, 12:44 PM@AkaSci it would need a better name than ED138, maybe Mini-Me 😜
@AkaSci
I'd love to see Mercury, Chiron, and Earth's Moon in that table for comparison...