Using a 33cm telescope 24 year old amateur astronomer Clyde W. Tombaugh discovered the dwarf planet in search for a ninth planet based on predictions of other astronomers.  He also observed the surfaces of Venus, Jupiter, Mars, Saturn, and the moon and discovered several clusters of stars and galaxies.

Other notable events on February 18th:

In 1978, Hawaii hosts the first Ironman Triathlon including 3.86 km of swimming, 180.25 km cycling and a 42.2 km running.

In 1977, the Space Shuttle, called “The Enterprise”  takes off on its maiden flight mounted on a Boeing 747 Shuttle Carrier Aircraft.

In 1929, the first Oscars are awarded.

In 1885, Mark Twain publishes the adventures of Huckleberry Finn.

Natural-color image of Pluto made from data acquired by the MVIC instrument on New Horizons on July 14, 2015. (I referred to NASA-released images for the hue shift from MVIC’s extended-spectrum composite.