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AkaSci 🛰️AkaSci@fosstodon.org
Oct 27, 2026, 10:28 PM
The Vera C. Rubin Observatory has discovered a new Dwarf Planet candidate in our solar system - 2026 ED138, a large, bright trans-Neptunian object orbiting beyond Pluto.
Distance from Sun: ~46 au (1 au is the average distance between the Earth and the Sun. Pluto has an average distance of 40 au)
Orbital tilt: 25°
Diameter: 600 - 1500 km
If confirmed, ED138 would be among the largest dwarf planets ever discovered in this region of the Solar System.
https://rubinobservatory.org/news/rubin-first-dwarf-planet-candidate
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Replies

AkaSci 🛰️AkaSci@fosstodon.org
Oct 27, 2026, 10:37 PM
A new NOVA | PBS documentary on the discovery of the Dwarf Planet 2026 ED138.
"How was it able to stay hidden for so long? Follow the story of how scientists made this discovery -- and what they still need to learn before it can be officially declared a dwarf planet, joining the club with Pluto, Ceres and others."
https://www.youtube.com/watch?v=8NIwXWwKOpw
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AkaSci 🛰️AkaSci@fosstodon.org
Oct 27, 2026, 10:40 PM
The NSF NOIRLab website has additional info, images and videos on Dwarf Planet candidate 2026 ED138.
https://noirlab.edu/public/news/noirlab2626/?lang=en
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AkaSci 🛰️AkaSci@fosstodon.org
Oct 28, 2026, 12:03 AM
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
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AkaSci 🛰️AkaSci@fosstodon.org
Oct 28, 2026, 1:29 AM
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
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AkaSci 🛰️AkaSci@fosstodon.org
Oct 28, 2026, 11:01 AM
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
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AkaSci 🛰️AkaSci@fosstodon.org
Oct 28, 2026, 11:47 AM
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.
https://www.youtube.com/watch?v=_ssnabPxqxk
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AkaSci 🛰️AkaSci@fosstodon.org
Oct 28, 2026, 1:04 PM
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.
https://stellarium-web.org/
For more detailed co-ordinates, see https://www.minorplanetcenter.net/db_search/show_object?object_id=2026+ED138
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Ahoaho@mastodon.social
Oct 28, 2026, 12:44 PM
@AkaSci it would need a better name than ED138, maybe Mini-Me 😜
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Den of EarthDenOfEarth@mas.to
Oct 28, 2026, 7:50 PM
@AkaSci
I'd love to see Mercury, Chiron, and Earth's Moon in that table for comparison...
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Ed Wiebeedwiebe@scribili.masto.host
Oct 27, 2026, 11:40 PM
@AkaSci Bright is relative, presumably.
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teledyn 𓂀teledyn@mstdn.ca
Oct 28, 2026, 12:07 AM
@edwiebe
If your telescope can see Pluto or Neptune, you might see this one, but 'seeing' requires stacking exposures
@AkaSci
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Taran Rampersadknowprose@mastodon.social
Oct 28, 2026, 12:01 AM
@AkaSci very cool. I remember reading something on speculation related to *an uknown* some years ago.
Now that it's known, what's next on the list? 🙃
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AkaSci 🛰️AkaSci@fosstodon.org
Oct 28, 2026, 12:07 AM
@knowprose
There is Planet Nine still waiting to be discovered.
https://en.wikipedia.org/wiki/Planet_Nine
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Taran Rampersadknowprose@mastodon.social
Oct 28, 2026, 12:10 AM
@AkaSci cool. Wondering is undervalued on our planet. 🙃
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✶Rayotron✶rayotron@mstdn.social
Oct 28, 2026, 1:11 AM
@AkaSci
Oh no, Planet 9 from Outer Space! The home of Vampira!
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Luchuco Cadáverlufertec@mastodon.uy
Oct 28, 2026, 3:20 AM
@AkaSci teléfono para @eMuleNews
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trainguyromtrainguyrom@techhub.social
Oct 28, 2026, 3:37 AM
@AkaSci ah crap now someone's gotta update KSP with another planet...
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Bonkersbonkers@nerdculture.de
Oct 28, 2026, 6:29 AM
@AkaSci look ma, they found a flying France
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