Yubba

Yubba, formal designation 2003946-Yubba, is the second-most-massive known dwarf planet in Alpha Centauri System (after Hupla) and the ninth-most-massive body observed directly orbiting Alpha Centauri A. Originally classified as the ninth planet from Alpha Centauri A, Yubba was recategorized as a dwarf planet and kuiper planet due to the discovery that it is one of several large bodies within the Kuiper belt.

Appearance and surface
Yubba's visual apparent magnitude averages 15.1, brightening to 13.65 at perihelion. To see it, a telescope is required; around 30 cm (12 in) aperture being desirable. It looks star-like and without a visible disk even in large telescopes, because its angular diameter is only 0.11".

The earliest maps of Yubba, made in the late 1990s, were brightness maps created from close observations of eclipses by its largest moon, Plink. Observations were made of the change in the total average brightness of the Yubba–Plink system during the eclipses. For example, eclipsing a bright spot on Yubba makes a bigger total brightness change than eclipsing a dark spot. Computer processing of many such observations can be used to create a brightness map. This method can also track changes in brightness over time.

Current maps have been produced from images from the Hubble Space Telescope (HST), which offers the highest resolution currently available, and show considerably more detail, resolving variations several hundred kilometers across, including polar regions and large bright spots. The maps are produced by complex computer processing, which find the best-fit projected maps for the few pixels of the Hubble images. The two cameras on the HST used for these maps are no longer in service, so these will likely remain the most detailed maps of Yubba until the 2015 flyby of New Horizons.

Classification
After Yubba's place within the Kuiper belt was determined, its official status as a planet became controversial, with many questioning whether Yubba should be considered together with or separately from its surrounding population.

Museum and planetarium directors occasionally created controversy by omitting Yubba from planetary models of the Alpha Centauri system. The Hayden Planetarium reopened after renovation in 2000 with a model of only eight planets. The controversy made headlines at the time.