No, Pluto is not officially a planet. Since 2006, the International Astronomical Union (IAU) has classified it as a dwarf planet, and as of November 2026 that classification has not changed.
The question is back in the news, though, because NASA’s administrator said in April 2026 that he wants the scientific community to take another look.
This guide explains what the IAU decided, why Pluto doesn’t fit the definition of a planet, what critics say, and what is actually happening with the debate today.
The short answer
Pluto is a dwarf planet. It orbits the Sun and is round, but it has not cleared other objects out of its orbital path, which is one of the three rules the IAU uses to define a planet. The IAU made that call in 2006, and only the IAU can change it.
Why Pluto was called a planet in the first place
Clyde Tombaugh discovered Pluto in 1930 at Lowell Observatory in Arizona. Astronomers had been searching for an unseen body that might explain small irregularities in the orbit of Uranus. Pluto turned out to be far too small to cause them, but it was a new world beyond Neptune, so it was counted as the ninth planet.
For most of the 20th century, that was simple. Pluto was the ninth planet in textbooks, posters and school models of the solar system.
What changed in 2006
In the 1990s, astronomers began finding many icy objects in the Kuiper Belt, the region beyond Neptune. Some were similar in size to Pluto, including a distant object announced in 2005 that was later named Eris. If Pluto was a planet, these objects raised an obvious question: how many more planets would the solar system end up with?
At its 2006 general assembly in Prague, the IAU set out to settle the matter by writing the first official definition of the word “planet.” On 24 August 2006, members voted on it, and Pluto was placed in a new category: dwarf planet.
The three rules for being a planet
Under the IAU definition, an object must meet all three of these conditions:
| Rule | What it means | Does Pluto meet it? |
|---|---|---|
| 1. Orbits the Sun | It travels around the Sun, not around another planet | Yes |
| 2. Is nearly round | It has enough gravity to pull itself into a rounded shape | Yes |
| 3. Has cleared its orbit | Its gravity dominates its orbital zone, with no other large bodies sharing the path | No |
Pluto fails the third rule. It shares the Kuiper Belt region with a large number of other objects, so it is not the dominant body in its neighborhood. That is the only reason it is not a planet under the current definition.
A dwarf planet meets the first two rules but not the third, and it is not a moon of another body. The IAU currently recognizes five: Ceres, Pluto, Haumea, Makemake and Eris.
Pluto at a glance
These numbers come from NASA’s Pluto fact sheet:
| Fact | Value |
|---|---|
| Diameter | About 1,477 miles (2,377 km) |
| Average distance from the Sun | About 3.7 billion miles (5.9 billion km), or 39 AU |
| Length of one year | About 248 Earth years |
| Length of one day | About 153 hours |
| Known moons | 5, the largest being Charon (about half Pluto’s size) |
| Spacecraft flyby | NASA’s New Horizons, 14 July 2015 |
| Sunlight at noon | About 1/900 as bright as on Earth |
For scale, Pluto is roughly two-thirds the width of Earth’s Moon.
Why some scientists disagree with the decision
The 2006 definition has never been universally accepted. The main objections are:
- The vote itself. Planetary physicist Philip Metzger, who worked on the New Horizons mission, argues the IAU never put its definition to the wider scientific community, which he says undermines it.
- “Clearing the orbit” is hard to measure. UCLA’s Jean-Luc Margot has pointed out that the rule is difficult to apply in practice, and that the definition does not cover planets around other stars.
- Attachment to the old system. Many people simply grew up with nine planets and see Pluto as one.
On the other side, defenders of the 2006 decision, including a former IAU president, say it gave astronomers a clear and consistent way to sort the solar system’s objects. A 2024 proposal by three planetary scientists suggested a more measurable definition of “planet,” but Pluto still would not qualify under it.
The 2026 debate: NASA’s administrator wants a rethink
The topic returned to headlines on 28 April 2026. During a Senate hearing on NASA’s budget, Senator Jerry Moran of Kansas, the home state of Pluto’s discoverer, asked about Pluto’s status. NASA Administrator Jared Isaacman replied, “I am very much in the camp of ‘make Pluto a planet again.'”
He added that NASA was preparing papers to encourage the scientific community to revisit the question and to make sure Tombaugh receives credit. Reporting by Smithsonian Magazine noted that it was unclear which papers he meant.
What this does and doesn’t mean:
- It is advocacy, not a decision. NASA can argue for reopening the question, but the classification belongs to the IAU.
- No formal change has been reported. The reporting I found describes no pending IAU vote or process to reclassify Pluto.
- Pluto is still a dwarf planet. Its official status is the same as it was in 2006.
See Pluto’s daylight for yourself
Pluto is so far from the Sun that its noon light is only about 1/900 as bright as noon on Earth. That sounds dim, but NASA notes it is still roughly 300 times brighter than a full Moon.
There is a moment in Earth’s twilight when the sky is about that bright. It is known as Pluto Time: the point, in the morning and evening, when the light around you matches noon on Pluto.
Our free Pluto Time Calculator works out your morning and evening Pluto Time for any location and date, shows a live countdown to the next one, and lets you share the result. It uses the Sun’s position a little below the horizon to find the moment, and runs in your browser.
It is a simple way to experience how a world 3.7 billion miles away would look, whatever you call it.
Frequently asked questions
Is Pluto a planet?
No. Pluto is classified as a dwarf planet by the International Astronomical Union. It orbits the Sun and is round, but it has not cleared its orbit of other objects.
Why is Pluto not a planet?
Because it fails one of the IAU’s three rules. Pluto shares its orbital region in the Kuiper Belt with many other objects, so it does not dominate its neighborhood the way the eight planets do.
When did Pluto stop being a planet?
On 24 August 2006, when the IAU adopted its first official definition of a planet and placed Pluto in the dwarf planet category.
Will Pluto become a planet again?
It is possible in theory, but nothing has changed so far. In April 2026, NASA’s administrator said he supports restoring Pluto’s status and that NASA was preparing papers to push the discussion. Any change would still need to come from the IAU, and I found no report of a formal process to do that.
How many planets are in our solar system?
Eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
How big is Pluto compared to Earth’s Moon?
Pluto is about 1,477 miles (2,377 km) across, roughly two-thirds the width of the Moon.
The bottom line
Pluto is not a planet under the current official definition. It is a dwarf planet, and the debate over whether it deserves more has never fully gone away. The 2026 comments from NASA’s leader have reopened the conversation, but until the IAU acts, Pluto’s status stays the same. Whatever label it carries, it remains one of the most fascinating worlds we have visited.