<P> Empirical observations suggest that the lower limit will vary according to the composition and thermal history of the object . For a body made of rigid silicates, such as the stony asteroids, the transition to hydrostatic equilibrium should occur at a diameter of approximately 600 km and a mass of 3.4 × 10 kg . For a body made of less rigid water ice, the limit should be about 320 km and 10 kg . In the asteroid belt, Ceres is the only body that clearly surpasses the silicaceous limit (though it is actually a rocky--icy body), and its shape is an equilibrium spheroid. 2 Pallas and 4 Vesta are rocky and are just below the limit . Pallas, at 525--560 km and 1.85--2.4 × 10 kg, is "nearly round" but still somewhat irregular . Vesta, at 530 km and 2.6 × 10 kg, deviates from an ellipsoid shape primarily due to a large impact basin at its pole . </P> <P> Many trans - Neptunian objects (TNOs) are thought to have icy cores and therefore would require a diameter of perhaps 400 km (250 mi)--only about 3% of that of Earth--to relax into gravitational equilibrium . As of January 2015, about 150 known TNOs are considered potential dwarf planets, although only rough estimates of the diameters of most of these objects are available . A team is investigating thirty of these, and think that the number will eventually prove to be around 200 in the Kuiper belt, with thousands more beyond . </P> <P> The IAU has recognized five bodies as dwarf planets since 2008: Ceres, Pluto, Eris, Haumea, and Makemake . Ceres and Pluto are known to be dwarf planets through direct observation . Eris is recognized as a dwarf planet because it is more massive than Pluto (measurements by New Horizons indicate that Pluto's diameter is larger than that of Eris), whereas Haumea and Makemake qualify based on their absolute magnitudes . In relative distance from the Sun, the five are: </P> <Ol> <Li> Ceres--discovered on January 1, 1801, 45 years before Neptune . Considered a planet for half a century before reclassification as an asteroid . Accepted as a dwarf planet by the IAU on September 13, 2006 . </Li> <Li> Pluto ♇--discovered on February 18, 1930 . Classified as a planet for 76 years . Reclassified as a dwarf planet by the IAU on August 24, 2006 . </Li> <Li> Haumea--discovered on December 28, 2004 . Accepted by the IAU as a dwarf planet on September 17, 2008 . </Li> <Li> Makemake--discovered on March 31, 2005 . Accepted by the IAU as a dwarf planet on July 11, 2008 . </Li> <Li> Eris--discovered on January 5, 2005 . Called the "tenth planet" in media reports . Accepted by the IAU as a dwarf planet on September 13, 2006 . </Li> </Ol>

What is the name of the dwarf planets