Astrophysicist David Gerdes<\/a>, the dean of the College of Arts and Sciences at Case Western Reserve University, told CNET via email that our understanding of solar system objects changes as we learn more about them. \u201cFor example, large asteroids like Ceres, Pallas and Vesta that orbit between Mars and Jupiter were originally considered planets when they were discovered in the early 1800s,\u201d Gerdes says.<\/p>\n \u201cAs more and more asteroids were discovered in this region, it eventually became clear that these objects were simply the biggest members of a very large population,\u201d he added. \u201cToday, we know of over a million asteroids \u2014 so many that we call that region the \u2018asteroid belt\u2019 \u2014 and nobody considers them planets.\u201d<\/p>\n But whether Pluto is a planet \u2014 and again, right now, it\u2019s not \u2014 comes down to how we decide to define the word \u201cplanet\u201d in scientific terms. But the tools we use to view the cosmos, like high-powered space telescopes, are getting better all the time. Every few years, it seems like we can see farther and clearer into space.\u00a0<\/p>\n Using these tools to discover new celestial objects was actually what got Pluto booted from its status as a planet in the first place. Here\u2019s what happened.\u00a0<\/p>\n A planet no more<\/p>\n In 2005, three astronomers discovered a distant, Pluto-sized celestial body and nicknamed it Xena, after the warrior princess from TV. The IAU official named it Eris<\/a>, after the ancient Greek god of chaos. It\u2019s a fitting name, as chaos ensued.\u00a0<\/p>\n Because Eris is roughly the same size as Pluto and shares many characteristics, Eris\u2019s discovery set off a fierce debate around what objects in space should be considered a planet. Eventually, this led the IAU to set out conditions that a celestial body must satisfy to be classified as a planet in 2006.\u00a0<\/p>\n According to the astronomers of the IAU, a celestial object needs to do three things<\/a> to be considered a planet. First, it must orbit a star. So, if it\u2019s a planet in our neck of the woods, it has to orbit the sun.\u00a0<\/p>\n Second, the object has to be big. If the object is big enough, it will have sufficient gravity to force it into a sphere. So, planets have to be a big ball. No flat planets allowed.\u00a0<\/p>\n Third, the planet also needs to be so large that it cleared anything else of similar size from its orbit. Obviously, moons and asteroids can be nearby, just not other planets.\u00a0<\/p>\n The IAU then set three categories for celestial bodies in our solar system: planets, dwarf planets and small solar system bodies. Dwarf planets have the same attributes as planets in this context, except they do not meet the third criterion: They have not cleared out the neighborhood around their orbits. Also, dwarf planets can\u2019t be satellites.\u00a0<\/p>\n The third category, small solar system bodies, is everything else orbiting the sun that\u2019s not a planet or a dwarf planet. Again, satellites don\u2019t count here.\u00a0<\/p>\n \u201cThese definitions are somewhat arbitrary, and people still like to debate them,\u201d Gerdes says. \u201cBut one thing is certain: There\u2019s no way to define a \u2018planet\u2019 that includes Pluto without also adding other objects like Eris, Sedna, Makemake and Ceres to the list.\u201d<\/p>\n So, unless we add more planets to the list, Pluto probably won\u2019t be reclassified as a planet. <\/p>\n \u201cModern science provides much more knowledge than the simple fact that objects orbiting the sun appear to move with respect to the background of fixed stars,\u201d the IAU president at the time, Ron Ekers, wrote in August 2006<\/a>.\u00a0<\/p>\n \u201cFor example, recent new discoveries have been made of objects in the outer regions of our solar system that have sizes comparable to and larger than Pluto. These discoveries have rightfully called into question whether or not they should be considered as new \u2018planets,\u2019\u201d he added.<\/p>\n \t\t\t\t\t\t\t![\"\"](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2026\/08\/IMG_1079.jpeg\")
Image of the dwarf planet Eris (also known as 2003 UB313 or Xena) that was taken using the Samuel Oschin Telescope at the Palomar Observatory.Screenshot by CNET<\/p>\n![\"Julian](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2026\/08\/65fa5541-7fc5-45fc-8fb8-d082bf0b8283.jpg\")
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