Pluto got the punt Thursday. Kicked out of the planet club after 76 years of membership.
Why? For being too small, not big enough to push away nearby neighbors lurking in its orbit. The poor little guy is now a “dwarf planet,” leaving just eight planets in the solar system (can you name them?).
How does something like this happen?
Come to find out, there’s an official group that makes these decisions, called the International Astronomical Union. And after much debate among astronomers, they changed the definition of a planet this week with a vote at a meeting in Prague.
So what is a planet?
Used to be a planet just had to revolve around the sun and reflect sunlight. Now, it has to revolve around the sun, be massive enough to let its own gravity shape it into a round shape, and “clear the neighborhood around its orbit,” or own its space. Interestingly, planet is Greek for “wanderer;” planets moved while stars stayed in a fixed position.
The decision to uproot Pluto was under debate for some time, though one camp of astronomers had wanted a broader definition that would save Pluto and incorporate even more planets.
Discovered in 1930 by a man named Clyde Tombaugh, Pluto is still a bit of a mystery as no spacecraft has ever made it to this far-out planet, which is 3.7 billion miles from the sun. It’s thought to be quite icy.
For now some scientists simply seem relieved to have put the issue at rest and move onto more science. We will likely know more in 2015 when New Horizons – a spacecraft launched in January of this year – should arrive at this lonely dwarf planet. It’s the textbook writers and museum curators who will be scrambling now to change the books and exhibits.
With Pluto out, does it really change our lives? Probably not. Just seems like the universe has shifted.