A forgotten Icy World

Pluto, once the ninth planet of our solar system, is now a mere dwarf planet outside the orbit of Neptune, a Trans-Neptunian object in the Kuiper's Belt. It was the first Kuiper belt object to be discovered, by Clyde Tombaugh at February 18, 1930 and was originally considered to be the ninth planet. Pluto is the second largest dwarf planet in the solar system after Eris, which is almost 30 times larger than it. Like other Trans-Neptunian objects, Pluto is entirely covered with ice and rocks.

Pluto's Perihelion that is the point in its elliptical orbit where it comes nearest to the Sun is about 29.66 Astronomical Units, with a gassy Methane-haze atmosphere. At its Aphelion, the point when its farthest away from the Sun is 49.3 Astronomical units. Here its atmosphere freezes completely.

Credits, Wikimedia Commons

The lost but beloved planet of all has a mass of 0.22 times the Earth's mass and a mean radius of about 1188 km. It has a surface pressure of one Pascal and it mainly consists of Nitrogen, Methane and Carbon Monoxide. Its orbital period around the Sun lasts 248 years, located at the Kuiper's Belt. The Kuiper's Belt also known as Edgeworth-Kuiper belt is a ring-shaped matter accumulation along the edge of the solar system towards the Oort cloud. It consists of gas, dust, asteroids, visiting comets and dwarf planets which were once in the protoplanetary disk around the sun when it was a Protostar, but now is a mere celestial fragment after formation of planets around it. It has three main dwarf planets Pluto, Haumea, and Make-Make. It is located approximately 50AU away from the Sun in a highly inclined orbit to the ecliptic. The bodies there are covered in ice and mainly consisted of Methane, carbon, ammonia, and water.

As the planets get further away from the Sun, their orbital speed decreases, Pluto has the Orbital speed of 4.67 km/s. It's the speed a Spacecraft must accelerate for moving around the sun and do a sun dive to travel to the inner solar system. Light takes an average time of 5.5 hours to reach Pluto. Pluto's orbit overlaps the orbit of Neptune, but the orbital resonance of 2:3 ratio, keeps them from colliding and helps remain stable. The velocity needed for escaping the gravitational influence of a celestial body is called the escape velocity. The escape velocity of Pluto is 1.212 km/s. The surface temperatures on Pluto reach up to a maximum of 55 K. One day on Pluto takes 6 days, 9 hours, and 17 minutes.

The apparent magnitude of Pluto is 15.1 and its absolute magnitude is -0.7. Apparent magnitude: Luminosity measure of a celestial object as it appears in the night sky of Earth. Absolute magnitude: The luminosity of object if viewed from a standard distance of 10 parsecs, where one parsec is 3.26 light year. Higher the numbers the dimmer the objects are.

It has been discovered that this small dwarf planet has five moons, and its largest moon is about one eight of its size. Its moons are Charon, Styx, Nix, Hydra, and Kerberos. Since the Charon is the largest moon of Pluto and its size comparable the parent planet, the center of mass of this two-body system is located exactly between the two bodies. This system is often considered Binary due to the Barycentre of orbits lying outside the body. There was also a proposal to name them as Twin planets or Binary Planets, but that proposal was soon rejected. Charon is tidally locked to Pluto. Other moons are much smaller than Charon and irregularly shaped.

Credits, Wikimedia Commons, http://photojournal.jpl.nasa.gov/jpeg/PIA20153.jpg

New Horizons spacecraft flew by Pluto in July 2015; it made detailed measurements and observations of it. It found on Charon's North Pole the organic molecules called Tholins, which might be the essential ingredient for building a life, which is birthed from gases released from Pluto's atmosphere.

Credits, Wikimedia Commons

On the planet’s equator a sea of frozen Nitrogen, Sputnik Planum, was discovered which was born out of an icy meteor crater. On January 5, 2005, Dr. Michael E.Brown and his team at Caltech discovered the Dwarf planet Eris, which is the only known Trans-Neptunian object larger than Pluto. This led to further scrutinizing of Pluto, then Ninth planet. On August 2006, The International Astronomical Union (IAU) defined the planets that orbit its home star. The International Astronomical Union (IAU) defined in August 2006 that, in the Solar System, a planet is a celestial body which: Planet should orbit its Parent star, have sufficient mass with a nearly round shape and a clear neighborhood around its orbit. Pluto only fit one of these descriptions. Pluto even being nearly round in shape did not possess more mass than the biggest dwarf planet and did not have a clear neighborhood because it overlaps the orbit of Neptune and laying in Kuiper's belt it's more to get hit by free-floating icy bodies. This led to IAU demoting and re-branding Pluto to a Dwarf planet.

Orbits of planets, Credits, Wikimedia Commons

Pluto now exists at the Kuiper belt, drifting along with its moons, orbiting around its parent star, but not the same as it used to be. Once the ninth planet of solar system, it is now demoted to a dwarf planet after 85 years from its discovery, due its insufficient mass to assume a hydro static equilibrium and a cleared neighborhood around the Planet. Pluto spins in the opposite direction of the Earth's motion around the Sun, that is it has a retrograde motion.