Welcome back Stargazers!
These next two blogs will focus on the last “planet” in our Solar System…. yes, we’ve finally come to meet and learn about Pluto, the dwarf and ninth planet known for its icy composition, five moons and unique orbit around the Sun!
Pluto was discovered in 1930 by Clyde Tombaugh, an American astronomer at the Lowell Observatory in Flagstaff, Arizona, while searching for a predicted ninth planet. However, in 2006, the International Astronomical Union (IAU) reclassified it as a dwarf planet due to its small size and icy environment. It apparently resides in the Kuiper Belt, a distant region beyond Neptune filled with icy bodies and debris.
Our ninth planet is composed primarily of ice and rock, with a mass roughly one-sixth that of the Moon and about one-third of the Moon’s volume. Its surface is dominated by nitrogen ice, with ice mountains, glaciers, and possible ice volcanoes. Evidence suggests a subsurface ocean of liquid (water?) which may exist beneath its icy crust. Pluto’s thin atmosphere consists mainly of nitrogen with trace amounts of methane and carbon monoxide.
Pluto has a non-circular, tilted orbit, and light takes about 5.5 hours to reach it. Its orbit occasionally brings it closer to the Sun than to Neptune. Pluto rotates on its axis and is gravitationally locked with its largest moon, Charon – which means Pluto’s spin rate matches its orbit, causing one side to permanently face the object it circles.
Moons are very important to the status of Pluto. There are five known moons: Charon, Styx, Nix, Kerberos, and Hydra. Charon is the largest of the moons, has the greatest influence, and it’s about half the size of Pluto. This moon exerts a massive gravitational pull-on Pluto, creating a system where both bodies are mutually locked by tides, sharing an external center of gravity and exchanging atmospheric gases.
NASA’s New Horizons spacecraft conducted a flyby of Pluto on July 14, 2015, providing the first close-up images and detailed measurements of its surface, atmosphere, and moons. This mission revealed Pluto’s complex geology, including mountains, plains, and potential icy volcanic activity, greatly enhancing our understanding of this distant world.
Even though in 2006, the IAU formally redefined the term ‘planet’ to exclude dwarf planets such as Pluto, there are many planetary astronomers [and we astrologers] who continue to consider Pluto and other dwarf planets to be Planets and members of our Solar System!
So, stargazers, continue to look at the Heavens. A Virgo New Moon appears in three days, on September 10, 2026, and offers a clean slate to set intentions around daily habits, wellness and job organization. Enjoy the nightly star display and – relax!
Yours in the Stars!
Astrid