Pluto

Poor Pluto was a planet,
But not for very long,
Before an orbit was over,
It had already gone quite wrong.

Percival Lowell proposed in 1906 to persue the postulated Planet X. Which was,
Perceived to be causing perturbations in the passage of Uranus about the sun.
With William Henry Pickering, who had already discovered Phoebe, mooning about Saturn,
Percival prepared photographic plates, but passed away, postponing further pursuance.
While his widow was locked in long, legal wrangling over his legacy.
But in 1929 an astronomer named Clyde Tombaugh, was put to work,
As the search resumed, he took pictures of his own,
Positioning the astrograph, to point at his predecessor's predicted piece of sky.
Then using the Pulfrich blink comparator to flick back and forth, between the plates,
He pinpointed a planet.

The name that was picked, was Pluto, which was proposed by Venetia Burney
An eleven year old from Oxford, who loved mythology.
Perhaps because ♇ combines perfectly P and L, it thereby references Percival Lowell.
And, as Roman God of the underworld, Pluto could make himself unseen,
Pertinent to a planet, perpetually in the shadows, and pretty near imperceptible.

But as time went by poor Pluto seemed to shrink, as estimated mass reduced again and again.
Then in 1978 there was found a mate.
Charon was either the first possible moon, or, perhaps, a binary partner.
For their barycenter lies outside the physical perimeter of primary Pluto.
Accurate assessment of the actual mass, arrived at 0.2% of that of Earth.
A particularly poor candidate for Planet X. Which was,
A perplexing puzzle till 1992, when Myles Standish, deliberating over data
From Voyager 2's approach to Neptune, deduced that planet's mass should be reduced,
And thereby discovered that the discrepancies that desired Planet X didn't exist.
Perhaps even, that Pluto was where the postulated X was proposed, was pure chance.

We learned that Pluto was part of the Kuiper Belt,
Which was populated with many more Trans Neptunian Objects.
Beyond that, there was Eris of the scattered disc.
In light of this, puny Pluto's position as a planet was reconsidered.
The International Astronomical Union declared
That for failing to clear the neighbourhood, Pluto should be demoted.
It was reclassified as a dwarf planet in 2006, though many protested.
Passing by, just nine years later, New Horizons posted a plethora
Of pictures and particle particulars from PEPSSI.
A postcard from Pluto, an ex-planet.

Rather wonderful from my point of view, I discovered by chance that I'm not the only one to have written a poem about Pluto.
Check out "Dwarf Planet"