July’s presentation is by Dr. Hal Levinson, who spoke to LAS last year about the Lucy Project, studying the Trojan asteroid swarms that preceded and follow along Jupiter’s orbit. This time Dr. Levinson will share his perspective on Pluto’s planetary status.

A little topical background. Pluto was demoted from planet to dwarf planet in 2006 by the International Astronomical Union [IAU]. When astronomer Mike Brown discovered the Kuiper Belt Object that is now named Eris, it created a dilemma: what defines a planet. Eris was thought to be much like Pluto, and it looked like there would potentially be several if not many more such objects lurking in the neighborhood. If Eris et.al. were accorded planetary status, where would it end? The IAU developed three criteria to be met for an object to be declared a planet: [1] orbit the Sun; [2] be essentially round; and [3] clear the area of other bodies, i.e., be the dominant object. Pluto, alas, only met the first two requirements.

One other note, this about our old friend Charles Pickering, who got fed up with the performance of his minions and hired his then maid Willemina Fleming, who in turn  went on to discover many objects including the inaccurately named Pickering’s Triangle in the Cygnus Loop [Veil Nebula]. Pickering was a planet hunter who collaborated with Percival Lowell looking for Planet X; neither found it. But before Clyde Tombaugh did finally spot Pluto, sixteen other observatories had actually imaged it, they just didn’t know it at the time.