Pluto: What has New Horizons discovered during its flyby of the dwarf planet?

The debate surrounding Pluto’s size has finally been settled, according to brand new results returned by NASA’s New Horizons spacecraft.

Pluto has been found to be about 2.370 kilometres (1,473 miles) in diameter, making it somewhat larger than previous estimates of the dwarf planet. Images taken by the Long Range Reconnaissance Imager (LORRI), confirms what astronomers already suspected: the dwarf planet is larger than all other known Solar System objects beyond the orbit of ice giant Neptune.

Check out our latest video where our very own Editor Jodie Tyley interviewed Gemma Lavender, owner of a Master’s degree in Astrophysics and Features Editor for All About Space magazine, to find out more about New Horizon’s discoveries…

A new estimate of Pluto’s size means that the dwarf planet’s density is slightly lower than previously thought and the fraction of ice found in its interior is higher. The atmosphere that encompasses the world is also shallower than initially thought. It’s because of Pluto’s atmosphere that astronomers have been unable to get a better idea of the dwarf planet’s size. Its largest moon Charon, on the other hand, doesn’t have a substantial atmosphere – that means that we’ve been able to determine just how big it is with relative ease using ground-based telescopes on Earth. Observations from New Horizons confirm previous estimates of 1208 kilometres (751 miles).

The dwarf planet’s icy surface is becoming more fascinating and complex. The spacecraft’s latest image suggests features that may be cliffs and impact craters, snow and even a large heart-shapes bright area measuring some 1,200 miles (2,000 kilometres) across, giving Pluto the nickname of the small planet with the big heart!


This graphic shows Pluto and its moon Charon if they were placed slightly above Earth, illustrating their size. Pluto has a diameter equivalent to 18.5% of Earth’s whereas Charon has a diameter equal to 9.5% of Earth’s.


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Plus, check out:

Pluto: What we know about the dwarf planet so far

NASA’s New Horizons spacecraft given “all clear” for Pluto flyby

Why is Pluto no longer a planet?