back to top

    Yesterday we celebrated Pluto Day

    Staying in a recent posts mood about the great astronomer Nicolaus Copernicus, we are obliged to mention Pluto Day celebrated each February 18.

    What is interesting, Pluto is much smaller than the Moon, and it takes five hours for sunlight to reach it (in comparison with 8 minutes to Earth). Pluto was formed 4.6 billion years ago.

    The period of intense planet hunting

    “The object formerly known as the planet Pluto was discovered on February 18, 1930 at the Lowell Observatory in Flagstaff, Arizona, by astronomer Clyde W. Tombaugh, with contributions from William H. Pickering. This period in astronomy was one of intense planet hunting, and Pickering was a prolific planet predictor.” (

    However, it is no longer the 9th planet in the solar system.

    In August 2006 the International Astronomical Union (IAU) downgraded the status of Pluto to that of  “dwarf planet.” This means that from now on only the rocky worlds of the inner Solar System and the gas giants of the outer system will be designated as planets. The “inner Solar System” is the region of space that is smaller than the radius of Jupiter’s orbit around the sun. It contains the asteroid belt as well as the terrestrial planets, Mercury, Venus, Earth, and Mars. The “gas giants” of course are Jupiter, Saturn, Neptune, and Uranus. So now we have eight planets instead of the nine we used to have.”(

    More in section