Pluto is officially a dwarf planet, in spite of protests. But Pluto is actually bigger than we thought. Measurements taken by the New Horizons spacecraft put the dwarf world’s diameter at 2,370 km (almost 70km larger than its 2006 measurement). “The new measurement has a number of implications,” reports the BBC. “The first is that it makes Pluto slightly less dense than we thought, meaning the fraction of ice in its interior is probably higher than we had recognized. The measurement also changes some of the expected properties of the atmosphere, given that the sphere it envelops is now considered to be larger. For modellers, it suggests the troposphere, the lowest layer, is a bit shallower.”
More importantly for those who would like to see Pluto designated a planet again, the new measurement might help restore its status. The discovery of similar-sized Eris in 2005 “was partly responsible for getting Pluto demoted from full planet status in 2006. However, this new result indicates that Pluto really does have the upper-hand, if only by about 30km in terms of diameter.” Nine years after New Horizons was launched, the NASA probe will fly by Pluto tomorrow morning. It will be pass only 12,500km above the planet just before 8:00 EDT.