Hubble's Universe Unfiltered

  • December 6, 2010

    Episode 15: Changing Views of Pluto

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    While it may seem that the astronomy community's views on Pluto changed radically with its reclassification in 2006, the truth is that our understanding of Pluto has always been shifting. This small, icy world in the distant reaches of the solar system is so difficult to observe that, even with Hubble's keen resolution, it only shows up as a few pixels in an image.

    Only with patience, lots of observations, and huge amounts of computing power have we been able to create approximate surface maps of Pluto and discover some surprising alterations to its surface. Improved imagery yields improved insight. We now comprehend Pluto's place within the solar system, and the exploration of that region has really just begun.

    • In the video podcast, I jokingly refer to "Percival Lowell's Greatest Mistakes" being 1.) the claim that Mars had a civilization using canals, and 2.) the prediction of a large planet beyond Neptune. Some may recognize this phrasing as an oblique reference to similar wording used in Douglas Adams' Hitchhiker series. (If you're going to steal, steal from the best.) However, please do not interpret this humor as a general condemnation of Percival Lowell. The man had incredible zeal for astronomy and used his energy, time, and wealth to further its development. The Lowell Observatory in Arizona is a tremendous legacy with more than a century of observation, research, discovery and outreach.

    • It bothers me that Hubble's maps of Pluto are often labeled as images. I especially don't like to see that in textbooks, giving schoolchildren the false impression that we know more that we really do. The fact that our best images of Pluto are still pixilated carries with it a powerful message of the small size and great distance to this object. The solar system is vast and not yet fully explored. There are limits to our knowledge and new worlds to uncover. Let's accept the ugly truth and embrace it as a challenge to make more discoveries in the future.

    • Here's a question to ponder: If Pluto is a large, but otherwise typical member of a family of thousands of Kuiper Belt Objects (KBOs), why did it take 63 years after Pluto's discovery to find the next one? While I can't answer this completely, here are three factors: size, color, and intense dedication. Most KBOs are tiny. Roughly a dozen or two have been detected so far with diameters one-half or larger that of Pluto. Most KBOs are dark. Pluto has bright frost covering enough of its surface to make it much, much brighter than other KBOs. Most observers are not Clyde Tombaugh. The patience, purpose, and skill, as well as the ever-important funding, to tackle a herculean task like that required to find Pluto is rare. When technology developed to find these small, dark objects without consuming excessive resources, the discoveries came quickly.

    • While it may take many years to get to Pluto and the Kuiper Belt, the New Horizons mission has done what science it could along the way. In addition to performing routine check-outs of its instruments, the spacecraft was able to make a number of observations during its flight past Jupiter (for a gravitational assist). One of my favorite solar system images ever is this image sequence of the eruption of the Tvashtar volcano on Jupiter's moon Io.

      Hopefully, such results are a sign of great things to come in 2015 and beyond.

    Image notes

    Pluto Discovery Plate Images
    Credit: Lowell Observatory Archives

    Pluto and Charon from a Ground-based Telescope
    Credit: Canada-France-Hawaii Telescope, Hawaii

    Pluto and Charon from Hubble in 1990
    Credit: NASA, ESA, and STScI

    Pluto Images and Globe Maps from Hubble in 1994
    Credit: Alan Stern (Southwest Research Institute), Marc Buie (Lowell Observatory), NASA and ESA

    Pluto Globe Maps from Hubble in 2002-2003
    Credit: NASA, ESA, and M. Buie (Southwest Research Institute)

    Rotation of Pluto Globe Maps from Hubble in 2002-2003
    Credit: NASA, ESA, and M. Buie (Southwest Research Institute)

    Pluto Rectangular Maps from Hubble in 1994 and 2002-2003
    Credit: NASA, ESA, and M. Buie (Southwest Research Institute)

    Map of Mars by Schiaparelli in 1890
    Credit: Giovanni Schiaparelli

    Launch of the New Horizons Mission from Cape Canaveral
    Credit: NASA

    Drawing of New Horizons Mission and Pluto System
    Credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

    Plot of Kuiper Belt Objects
    Credit: Minor Planet Center and F. Summers (STScI)