A Closer Look at the Pluto Photos


We did it! After nine and a half years of travel, the New Horizons spacecraft has finally reached Pluto. In an instant, this indistinct dot of dim light has now become yet another brilliant world known by humans in glorious detail!

Pluto before 2003, (left=telescope) and after 2015 (right=New Horizons)

It is hard for me as an astronomer to express how thrilling it is to see something clearly for the first time. For all my life since grade school in the 1960s, the only thing I have ever known about Pluto’s appearance has been a photograph of its star-like shape. Again and again it has been photographed by powerful telescopes on Earth, but they still only reveal it as a dot of light among the star fields. This changed only slightly when in 2003, some 73 years after discovery, the Hubble Space Telescope took its series of photographs of Pluto.

After intense computer modeling an image of sorts was created that showed persistent surface blotches hundreds of kilometers across. Its vast distance of nearly six billion kilometers, together with its diminutive diameter of only 2,360 km means that from Earth, no matter what you try to do, its angular size is only 0.08 seconds of arc or 0.00002 degrees. Our moon in the sky is a full 0.5 degrees and 1800 seconds of arc in diameter! Thinking about it another way, Pluto appears as large as the diameter of a U.S. penny seen at a distance of 30 miles! New Horizons can easily discern features smaller than Lincoln’s eyeball!

In a matter of a few months earlier this year as New Horizons approached Pluto, its best images only matched Hubble’s at a resolution of about 500 km per pixel, but by May they were ten times better. At its —> Read More