Those who miss the good old days when Pluto was still a planet can celebrate the fact that 90 years ago, on Feb. 18, 1930, the small, rocky space object was discovered.
Pluto fast facts
Pluto orbits the sun from about 3.6 billion miles, which is roughly 40 times farther than the Earth. The dwarf planet is smaller than the Earth's moon at 1,400 miles in diameter. It moves slowly and in an elliptical orbit. One day on Pluto lasts almost six Earth days, and a year takes 248 Earth years. The composition is rocky with a thin atmosphere, which, combined with the distance from the sun, makes the surface very cold (-369° F to -387° F).
»PHOTOS: First glimpses of Pluto and its moon
Eureka! Pluto’s discovery
According to nineplanets.org, astronomers starting in the 1840s speculated there must be some large object beyond Neptune that was impacting its orbit. Researcher Percival Lowell called this mystery object "Planet X" and devoted his time at the Lowell Observatory in Arizona trying to discover it. Lowell captured images of what we now know as Pluto during his studies, but the search lapsed after his death in 1916.
In 1929, Clyde Tombaugh started the search for Planet X while working for Lowell Observatory at age 23. One year later, he discovered it.
Credit: Wikimedia Commons
Credit: Wikimedia Commons
A new technology consisting of photographic plates combined with a blink microscope aided Tombaugh in his studies and allowed the discovery to be confirmed.
An 11-year-old from Oxford, England, reportedly suggested the name Pluto, and it was selected during a vote in May 1930. Many liked the name because it contained the initials of Lowell, whose work led to Tombaugh’s discovery. Another explanation says Pluto was named after the god of the underworld in ancient Roman mythology.
Pluto’s demotion
In 2006, The International Astronomical Union updated qualifications for a space body to be considered a planet. Pluto, which was the ninth and last planet to be discovered, was demoted under new guidelines because its orbit crossed Neptune’s. According to a 2006 general assembly, a planet is now defined as:
"A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit." — International Astronomical Union
The IAU is still in the process of defining exactly what category Pluto belongs in. It now calls Pluto a dwarf planet, along with two other space bodies called Ceres and Eris. Trans-Neptunian objects or even “plutoids” are terms used to describe small, rocky space objects closely outside our current solar system.
This decision prompted “widespread outrage” from popular culture, according to NASA. The internet depicted Pluto as a heartbroken, rejected being.
In 2006, the verb plutoed was voted as the word of the year. To "pluto" is to "demote or devalue someone or something," says The American Dialect Society.
Even NASA officials disagree with Pluto’s standing.
"Just so you know, in my view, Pluto is a planet, and you can write that the NASA administrator declared Pluto a planet once again...I'm sticking by that. It's the way I learned it, and I'm committed to it." — NASA administrator Jim Bridenstine
»RELATED: Will Pluto regain its planetary swagger? Scientists are pushing for it
Since the IAU decision however, a 2015 NASA mission has prompted interest again in the lonely ex-planet.
Photographs from the New Horizons spacecraft showed Pluto to have glaciers, blue skies, mountains, moons and even red snow.
"The complexity of the Pluto system — from its geology to its satellite system to its atmosphere — has been beyond our wildest imagination. Everywhere we turn are new mysteries." — Alan Stern, New Horizons principal investigator
Researchers are continuing to process data gathered from the New Horizons mission, but New Horizons principal investigator Alan Stern still looks forward to more visits ahead.
According to a space.com article, one dream is to launch a mission in 2030, 100 years after Pluto's discovery, potentially to land on Pluto moon Charon or orbit the planet for better footage.
“The curtain is opening,” Stern said of the Pluto orbiter idea. “This thing is going to be a topic of discussion now for the next few years.”
Happy 90th anniversary of discovery, Pluto!
