Universe Guide

Home / Facts


Pluto is the ex-nineth planet from the Sun. It is now classed as a dwarf planet, too big and too spherical to be classed as an asteroid but its path is not cleared. The planet is classed as a dwarf planet. Pluto derives its name from the Roman god for God of Death. Pluto was discovered by Clyde Tombaugh in 1930. Since 2006, Pluto is no longer deemed to be a planet like Earth, it now known as a dwarf planet, a planet that amongst other things has not cleared its path round the Sun. The mass of the object is 0.0125. The equatorial radius of the planet is 1195 whereas the volumetic mean radius is 1195. The Mean Density of the planet is 1750. The surface acceleration of the planet is 0.58. The time the planet takes to revolve round the Sun is 90560 days or roughly 248.1 Earth Years. The length of a day on the planet is 153.282 hours, i.e. the time it takes to revolve once on its axis. The average temperature of the planet is -50K/-223C. The surface pressure of the planet is -3 microbars.

Pluto is about 5870000000km from the Sun. The Orbit Eccentricity is 0.2444, that is how much the orbit deviates from a circle, between 0 and 1. The Orbit Inclination is -3, that is how much the orbit deviates from a circle, between 0 and 1. The volume of Pluto at the equator is 0.715. The escape velocity, the speed which is need to break free is 1.1. The surface gravity of Pluto is 0.58 compared to Earth which for purpose of this site is 1. The following gasses can be found in the Pluto's atmosphere : Methane (CH4), Nitrogen (N2)\n. More information and the source for the moon can be found at N.A.S.A.

Discovery and its Planetary Classification

The dwarf planet was spotted by Clyde Tombaugh as he scanned photos of the sky looking for any differences in the pictures.

Since its discovery in the 1930s until 2005, Pluto was a planet, the most distant from the Sun. However when astronomers discovered the kuiper belt object Eris in 2003, its days of being a planet were numbered. Eris with its companion moon Dysnomia was calculated to be larger than Pluto. Scientists didn`t want to call it a planet and came up with a three point law on what constitutes a planet. In a vote at the end of a meeting of the International Astronomical Union, the world governing body for all things to do with space, a vote was held on the law and was passed. The requirement for a planet are :

- is in orbit around the Sun
- has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a nearly round shape
- has cleared the neighbourhood around its orbit.

As Pluto failed the third test, it was no longer considered a planet and demoted. The third rule is a flawed rule and could rule out Earth as a planet because some asteroids have been known to cross it path. There are plans afoot to reclassify it. The lead scientist on the New Horizons project was extremely scathing of the downgrading saying it stunk but could have used harsher words. The planet is named after the Roman God of the Underworld. It is not named after the Disney dog of the same name. It was named by Venetia Burney, a British school girl who entered a competition to name it.

New Horizons Space Probe

Pluto was the last "planet" to be visited by a space craft but that is all about to change, the N.A.S.A. space probe, New Horizons is currently on route to rendezvous with the "planet" on or about 14th July 2015. New Horizons is the fastest space craft built to explore the outer regions of the space. It took Cassini-Huygens just over three years to reach the orbit of Jupiter, the New Horizons craft took a third of that time.

New Horizons only flew past the planet because the probe didn`t have enough fuel to slow it down. Had it had the necessary fuel to slow it down, it would`ve taken longer to get there. Pluto is not the end of the journey for New Horizons, it is carrying on to rendezvous with an asteroid in the Kuiper Belt called 2014 MU69 and will get there at the beginning of 2019. ref: N.A.S.A.

According to scientists looking at the data that has come back from the New Horizons probe, they believe they discovered water ice on the planet. Where there`s water, there could be life albeit at a very basic microbial level. The New Horizons probe was not equiped with any devices that could confirm any life forms on the planet. Life on such a cold and far off planet, that would be something. N.A.S.A.

Disney`s Pluto Dog

Before anyone gets the wrong idea, lets clear a thing up about it and a certain cartoon animal. Pluto is not named after a cartoon dog. Disney named its cartoon dog Pluto in honour of the discovery, not the other way round. Pluto was named after the Ancient Roman God Pluto, God of the Underworld as mentioned above. All the other planets in the solar system except Earth is named after a Roman God so it made sense to continue the ritual.


Pluto had for most of the time it was known was seen as a lonely planet like Mercury and Venus but on the 22nd June 1978, its first moon was discovered by James Christy at the United States Naval Observatory. After New Horizons was launched, its other moons were discovered starting with Nix in 2005. All the moons are named after a connection to the underworld to keep consistent.

Life on Pluto

There is no intelligent life, no Plutonians living and breathing on the planet. One of the surprising things that was discovered by the New Horizons mission was evidence of water on the planet and there might be an ocean on the planet. Any water would be frozen unless there`s an underground heat source. Where there is water, there could be life in the form of microbial life forms. Life exists in the harshest of atmospheres here on Earth so why not on Pluto. ref:Astrobio

There is unlikely to be any compex lifeforms on Pluto. However, as the Sun grows, it will get bigger and the Goldilocks Zone will move out and one day that zone will encompass Pluto. By the time the zone reaches Pluto, Earth will no longer be able to support life as we know it. Hopefully by that time, humanity has managed to find a way off the planet and living further out than Pluto.

Search for a new nineth planet

Scientists believe there might be another planet out beyond the orbit of Pluto, a new nineth planet. It is all theory at the moment but one day, we may well find out if there is any large planets out beyond Pluto. There might well be more than just one planet beyond Pluto, may be tens, all too faint to be spotted by telescopes at the present.

One of the strongest drivers for there being another planet out there is the paths of objects in the Kuiper Belt which seemingly behave differently to how they are supposed to be. There is a theory that the reason is caused by the nineth planet that was chucked out of the solar system at the beginning. As its so far away its hard to see and you definately won`t be able to see it looking up into the nights sky.

Pluto Facts

Position from Sun9th but no longer class as planet, dwarf planet instead
MeaningGod of Death
DiscovererClyde Tombaugh
Equatorial Radius1195
Volumetric Mean Radius1195
Mean Density1750
Surface Acceleration0.58
Orbital Period90560 Days
Length of Day153.282
Average Temperature-50K/-223C
Surface Pressure-3 microbars
Distance from the Sun5870000000km from the Sun.
Orbit Eccentricity0.2444
Orbit Escape Velocity1.1
Surface Gravity0.58
AtmosphereMethane (CH4), Nitrogen (N2)\n

List of Moons in orbit around Pluto

MoonDiscoveredOrbit Circumference
CharonJune 22, 1978 110,181.80 km

Add a Comment

Email: (Optional)