# Discovery and Physical Characterization of a Large Scattered Disk Object at 92 AU

## TL;DR

This paper reports the discovery and detailed physical characterization of a distant trans-Neptunian object, likely a dwarf planet, including its orbit, stability, and physical properties like size and albedo.

## Contribution

It presents the first detailed physical and orbital analysis of a newly discovered trans-Neptunian object at 92 AU, including thermal emission measurements and stability assessments.

## Key findings

- Object has a diameter of approximately 635 km.
- Albedo is estimated at around 13%.
- Orbit is stable over Gyr timescales with weak Neptune interactions.

## Abstract

We report the observation and physical characterization of the possible dwarf planet \UZ\ ("DeeDee"), a dynamically detached trans-Neptunian object discovered at 92 AU. This object is currently the second-most distant known trans-Neptunian object with reported orbital elements, surpassed in distance only by the dwarf planet Eris. The object was discovered with an $r$-band magnitude of 23.0 in data collected by the Dark Energy Survey between 2014 and 2016. Its 1140-year orbit has $(a,e,i) = (109~\mathrm{AU}, 0.65, 26.8^{\circ})$. It will reach its perihelion distance of 38 AU in the year 2142. Integrations of its orbit show it to be dynamically stable on Gyr timescales, with only weak interactions with Neptune. We have performed followup observations with ALMA, using 3 hours of on-source integration time to measure the object's thermal emission in the Rayleigh-Jeans tail. The signal is detected at 7$\sigma$ significance, from which we determine a $V$-band albedo of $13.1^{+3.3}_{-2.4}\mathrm{(stat)}^{+2.0}_{-1.4}\mathrm{(sys)}$ percent and a diameter of $635^{+57}_{-61}\mathrm{(stat)}^{+32}_{-39}\mathrm{(sys)}$~km, assuming a spherical body with uniform surface properties.