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TueFeb 18

Pluto Day – February 18, 2025

Pluto Day is celebrated annually on February 18 to commemorate the anniversary of the discovery of Pluto in 1930. The planet, known for its characteristic icy mountains and tiny size was discovered by American astronomer Clyde Tombaugh and, up until 2006, was considered one of the nine planets in the solar system together with Mercury, Venus, our current planet of Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Clyde discovered Pluto at the Lowell Observatory in Flagstaff, Arizona just 84 years after the discovery of Neptune.

History of Pluto Day

Pluto Day is celebrated annually to commemorate the anniversary of the discovery of Pluto in 1930. Although Pluto was discovered in 1930, the story of its discovery started in 1840 after French astronomer Urbain Le Verrier sensed that there was a planet outside of Uranus due to irregularities in its orbit. His intuition led him to develop mathematical calculations to explain the discrepancies of Uranus’s orbit in relation to the laws of planetary motion and gravity, which led to the eventual discovery of Neptune.

After Neptune was discovered, an event that is widely regarded as a validation of a subset of the astronomy practice called celestial mechanics. It was then realized that there was yet another planet disturbing Uranus’s orbit since the irregularity in its orbit continued. This then led to the search for Pluto — initially called Planet X — being headed by Percival Lowell, whose death would later see the search for Pluto passed to Clyde Tombaugh, who eventually discovered it.

The planet, which was named after the Roman god of the Underworld, was considered one of the nine planets in the solar system up until 2006. The International Astronomical Union reduced its status and tagged it a ‘dwarf’ planet due to not meeting the criteria to be considered a full-sized planet and being two-third of the size of the earth. It is believed that the first two letters in ‘Pluto’ were in honor of Percival Lowell whose belief that there were other planets beyond Neptune, helped fuel the drive that led to its discovery.

Pluto Day timeline

The Birth Of Clyde William Tombaugh

The birth of American astronomer and the discoverer of Pluto, Clyde William Tombaugh, occurs on February 4.

The Discovery Of Pluto

Tombaugh officially discovers Pluto at Lowell Observatory in Flagstaff, Arizona.

A Designated National Historic Landmark

The Lowell Observatory receives its status as a National Historic Landmark from the National Park Service.

Pluto — a Dwarf Planet

The International Astronomical Union reduces Pluto’s status (as a planet) and tags it ‘dwarf’, saying that it didn’t meet the criteria to be considered a full-sized planet.

Pluto Day FAQs

How do we celebrate Pluto Day?

On Pluto Day, try to watch a documentary about Pluto or visit your nearby planetarium and learn more about astronomy. You might even set up a telescope of your own to probe through the night’s sky to outer space to see if you can find known planets or even discover one for yourself.

Is Pluto still a planet?

Pluto was downgraded to a dwarf planet from a full-sized planet by the International Astronomical Union in 2006.

How long is a year on Pluto?

The hour Pluto needs to completely orbit the sun is equivalent to 6.4 Earth days or 153.3 hours long. Its full-year is equivalent to 248 years on Earth.

Pluto Day Activities

  1. Watch a documentary about Pluto

    Watching a documentary about Pluto is perhaps the closest thing to traveling to the planet or celebrating it here on earth. There are several documentaries, like “The Year of Pluto,” “Mission Pluto,” or “Chasing Pluto,” that all provide a great way to escape to the planet and see what it’s like in it through the eyes of astronauts. You might even share your opinion about any of these documentaries on social media using #PlutoDay.

  2. Read about planets

    Another interesting way to celebrate Pluto Day is to dive into astronomy books and research papers that talk about the properties of the various planets in our universe and what life looks like on every known planet. You may even visit the National Aeronautics and Space Administration (NASA) website to learn about its ongoing missions.

  3. Set up a telescope

    On Pluto Day, planetariums, observatories, and other places that study the solar system would typically hold special events. However, you might find a greater interest in setting up your own telescope to probe through the night’s sky to outer space and see if you can find known planets or even discover one for yourself!

5 Things You Didn’t Know About Pluto

  1. It has five known moons

    According to astronomers, the dwarf planet has five orbiting satellites.

  2. Pluto and nitrogen

    Pluto’s atmosphere is said to consist mostly of nitrogen gas.

  3. Pluto’s is a 153.3-hour long day

    Pluto is 40 times farther away from the sun than the earth, making its orbit slow; the hour it needs to complete orbit is equivalent to 6.4 Earth days or 153.3 hours long.

  4. Lowell Observatory and Pluto

    Pluto might have been named after the founder of the astronomical observatory it was discovered in.

  5. Pluto and the gods

    The planet is said to have been named after the Roman god of the Underworld, Pluto, based on the suggestion of an 11-year old girl from Oxford, England.

Why We Love Pluto Day

  1. It celebrates astronomy

    Pluto Day represents a reminder of the importance of the ancient practice of astronomy. The day aims to drive the interest of younger Americans to study astronomy through curiosity about the outside world. It serves as the day when everyone is reminded of the advances in knowledge of our universe that have been possible through the disciple.

  2. To reflect on our existence in space

    Although as humans we like to think we’re living at the edge of space making comments like ‘The satellite is out in space,’ the Earth is, in fact, part of space and we are currently in it. Pluto Day provokes this kind of reflection of our existence in the world.

  3. It’s a reminder to appreciate earth more

    On Pluto day many more people typically realize how lucky we are that Earth — one of many planets in the galaxy, just so happens to be hospitable for life as we know it today in contrast to the hostile and merciless environment of the other planets in our galaxy. The holiday serves as a reminder of how precious our planet is amongst others in the universe.

Pluto Day dates

2025February 18Tuesday
2026February 18Wednesday
2027February 18Thursday
2028February 18Friday
2029February 18Sunday

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