What is Pluto?
Pluto is a small, icy world that orbits the sun far out in the solar system. Itās only about half the width of the United States, and itās so cold that its surface is mostly frozen nitrogen.
But what Pluto lacks in size and warmth, it makes up for in personality. This planetary body has captivated the hearts and minds of millions of people all over the world.
Is Pluto a Planet?
As of today in 2024, Pluto is actually a dwarf planet that is located in the Kuiper Belt, a region of the solar system beyond Neptune.
Itās about 3.67 billion miles from the sun, making it the most distant known object in the solar system.
Pluto is only about 1,473 miles wide or about half the size of the United States and has a very thin atmosphere.
Despite its distance from the sun, Pluto is an interesting world to explore.
Pluto is compositionally similar to many other objects inhabiting the Kuiper belt. Letās explore Pluto further and take a look at its surface.
The Surface of Pluto
The surface of Pluto is characterized by a varied terrain of ice mountains, plains, valleys, and craters.
Pluto gets its reddish-brown tint due to the presence of tholins, complex hydrocarbon molecules produced from the interaction of ultraviolet light and nitrogen in the atmosphere.
There are also signs on Pluto of past geological activity, including possible cryovolcanism and tectonic activity. There are also signs of past glaciations on its surface.
However, there is no direct evidence of current geological activity.
Who Discovered Pluto?
American astronomer Clyde Tombaugh was searching for a planet beyond Neptune. He finally found it when he spotted a āmoving objectā in one of his telescopeās photographs.
This moving object turned out to be Pluto! Pluto was officially classified as a planet soon after its discovery.
When was Pluto Discovered?
Pluto was discovered on February 18, 1930, by the aforementioned Clyde William Tombaugh from the Lowell Observatory located in Flagstaff, Arizona. Tombaugh was an American astronomer who is also known for discovering many asteroids.
So, Is Pluto a Planet or Not a Planet?
For many years, Pluto was officially considered to be the ninth major planet in our solar system.
After 1992, its status as a planet was questioned following the discovery of several objects of similar size in the Kuiper belt.
In 2005, Eris, an object comparable to Pluto in size, mass and orbital characteristics, was discovered.
As a result a debate was opened on what exactly defines a āplanetā.
As a result, Pluto was eventually reclassified as a ādwarf planetā by the International Astronomical Union (IAU).
When did Pluto Stop Being a Planet?
On August 24, 2006, the International Astronomical Union (IAU) made a historic decision that changed the way we think about our solar system. They decided that Pluto is no longer a Major planet. Rather it was reclassified as a āDwarf planetā.
Why is Pluto No Longer a Planet?
Pluto was once considered to be the ninth major planet in our solar system, but as discussed, it was later reclassified as a dwarf planet.
This reclassification was made in 2006 by the International Astronomical Union (IAU), the organization responsible for classifying celestial objects.
The reason for this reclassification is because the IAU established a new definition of a planet, which requires a celestial body to meet three criteria:
- It must be in orbit around the Sun.
- It must have sufficient mass to assume a nearly spherical shape.
- It must have cleared its orbit of other debris and be the dominant object in its orbit.
Pluto failed to meet the third criteria, as it shares its orbit with many other objects in the Kuiper Belt, a region beyond the orbit of Neptune that is also home to numerous dwarf planets and other small bodies.
Therefore, based on the new definition, Pluto was reclassified as a dwarf planet, a subcategory of planet that includes other small and icy objects in our solar system.
Should Pluto be Classified as a Major Planet?
Even though Pluto is located in our Solar System and orbits the Sun, the major debate about Pluto being a Major planet centers mostly around Plutoās orbit and the criteria used to determine and define a planet as descussed above.
All of the other 8 major planets are much larger than Pluto. It is actually about half the size of the United States.
In our (biased) opinion, even though Pluto is classified as a Dwarf planet, we think that it still should be listed as the 9th planet along with the other 8 major planets which are (in order):
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- and Neptune. (Pluto was the 9th listed major planet until 2006).
How to See Pluto
You can view Pluto from a telescope. What you will need however, is a powerful telescope.
Additionally, If you want to get a good look at Pluto, the best time to do it is during the dark hours of night.
Because Pluto appears as a faint star, You will need a telescope with a large aperture to view it.
Does Pluto Orbit the Sun?
Yes, Pluto does orbit the Sun. Plutoās orbit is actually a bit of an eccentric situation. It doesnāt orbit the sun in the same way that Earth and other planets do.
Instead, its orbit is more elliptical. And, because of this, there are times when Pluto is closer to the sun than Neptune is.
So, technically and scientifically speaking, Pluto definitely orbits the sun. But, itās not a traditional circular orbit like weāre used to seeing.
How Large is Pluto?
Pluto is relatively smallāabout half the width of the United States (1,473 milesāand has an eccentric and highly elliptical orbit.
Plutoās orbit takes it as far as 49 AU (7.4 billion km) from the Sun and brings it closer to the Sun than Neptune for 20 years out of the every 248 years it completes its orbit around the Sun.
Pluto has a radius of 1,188 kilometers and a diameter of 2,376 kilometers. This gives Plutos a diameter of about 2/3rds of that the Moon.
It has an average density of about 2 g/cm3 (0.076 lb/cu in), or approximately 60% that of water. It is composed of approximately equal parts of rock and ice by mass.
Does Pluto have Moons?
Yes, Pluto has 5 Moons:
- Charon (the largest moon, with a diameter just over half that of Pluto),
- Styx
- Nix
- Kerberos
- And Hydra
Pluto and Charon are sometimes referred to jointly as a binary system.
This is because they are so close in size relative to their separation that they share an equal gravity field.
If one considers them separately, then Charon is classified as a moon of Pluto.
Pluto to Earth Distance? (And Sun)
At itās furthest distance (during itās elliptical orbit), Pluto is about 4.6 billion miles (4.8 billion kilometers) from earth. Thatās about 40 times the distance from Earth to the sun!
At itās closest point, Pluto is 2.66 billion miles away from Earth. This major discrepancy in distance is due to Plutos highly elliptical orbit.
As mentioned, Plutoās orbit is highly elliptical, with an average distance from the sun of about 3.67 billion miles (6.0 billion kilometers).
Because of their different orbits, sometimes Pluto can be closer to the sun than Neptune is.
When this happens, we say that Neptune is āout of sorts.ā But no worries, this only happens for only about 20 years during its 248 year orbit.
Does Pluto have an Atmosphere?
Pluto has a thin and tenuous atmosphere composed primarily of nitrogen (N2), methane (CH4), and carbon monoxide (CO).
Plutoās atmosphere is not well understood, but it is thought to be in a constant state of flux due to changes in temperature and the escape of volatile gases into space. It also has a weak and variable surface pressure
The atmospheric pressure on Pluto is only about 1/100,000th that of Earthās atmosphere at sea level! So itās pretty safe to say you wouldnāt want to breathe it in.
The average temperature on Pluto is minus 232 degrees Celsius or minus 387 degrees Fahrenheit. This would make for a very cool day on Earth to say the least!
What is Pluto Made of?
Pluto is composed primarily of rock and ice. Its composition includes:
- Nitrogen (N2): The main component of Plutoās atmosphere, making up over 80% of its gas envelope.
- Methane (CH4): A hydrocarbon that is present in trace amounts in Plutoās atmosphere, where it absorbs red light and gives the planet its distinctive reddish hue.
- Carbon Monoxide (CO): A gas that is also present in Plutoās atmosphere and contributes to its overall composition.
- Water Ice: The solid form of water (H2O) that covers much of Plutoās surface and is thought to be a major component of its interior.
- Rock: The solid material that makes up Plutoās interior and surface features, including its heart-shaped region. This is known as the Tombaugh Regio. This rock is thought to be a mixture of silicates, such as feldspar, and other minerals, including iron and magnesium.
The ice on Pluto includes water ice, as well as frozen nitrogen, carbon dioxide, and methane ices.
One fascinating fact about Pluto is that it has giant ice volcanoes on it. Pluto, however is not classified as an ice giant.
Pluto Summary: Key Points
- It is about half the width of the United States (1,473 miles).
- Its surface is mostly nitrogen ice with methane and carbon monoxide ices.
- Pluto has five moons: Charon, Styx, Nix, Kerberos, and Hydra.
- Despite its small size and remote location, Pluto continues to fascinate scientists and the public alike.
- Pluto is located in the solar system!
- It was discovered in 1930 by Clyde Tombaugh and was originally considered the ninth planet from the sun.
- Its orbit is elliptical in that it is not circular and it crosses Neptuneās orbit.
- In 2006, Pluto was officially re-classified as a ādwarf planetā by the International Astronomical Union (IAU).
- Pluto is located in the Kuiper Belt, which is a region beyond Neptune.
Questions & Answers
Q. What is the largest moon of Pluto?
A. Charon
Q. When was Pluto demoted from a planet to a dwarf planet?
A. August 24, 2006
Q. Who discovered Pluto?
A. Clyde Tombaugh
Q. What is the average temperature on Pluto?
A. Minus 387 degrees fahrenheit.
Q. What is the atmosphere of Pluto mainly composed of?
A. Nitrogen
Q. How long is a day on Pluto?
A. 6.4 Earth days
Q. How long is a year on Pluto?
A. 248 Earth years
Q. What is the orbital path of Pluto around the Sun?
A. Elliptical
Q. What is the average distance from Pluto to the Sun?
A. 3.67 billion miles
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