The trans-neptunian object UB313 is larger than Pluto.

Area of Science:

• Astronomy and astrophysics
• Planetary science
• Solar System dynamics

Background:

• 2003 UB313, a distant Solar System object, was discovered near aphelion.
• Its orbital characteristics (high eccentricity, inclination) classify it as a 'scattered disk' object.
• Scattered disk objects likely originate from the Kuiper Belt, a region of icy bodies beyond Neptune.

Purpose of the Study:

• To determine the actual size and surface properties of 2003 UB313.
• To compare 2003 UB313 with Pluto and other trans-Neptunian objects.
• To understand the composition and reflectivity of distant Solar System bodies.

Main Methods:

• Observations of thermal emission at a wavelength of 1.2 mm.
• Combined thermal emission data with optical brightness measurements.
• Calculated diameter and albedo based on observed data and accounting for measurement uncertainties and object orientation.

Main Results:

• 2003 UB313 has a diameter of 3,000 +/- 300 +/- 100 km, making it larger than Pluto (2,300 km).
• The object's albedo is 0.60 +/- 0.10 +/- 0.05, indicating a highly reflective surface.
• The albedo is similar to Pluto's, suggesting a methane-induced icy surface composition.

Conclusions:

• 2003 UB313 is the largest known trans-Neptunian object.
• Its surface composition is likely icy and highly reflective, similar to Pluto.
• This finding contributes to our understanding of the diversity and properties of objects in the outer Solar System.