Is Pluto a planet? A dwarf planet? An Exoplanet?
Pluto is a dwarf planet, a Trans-Neptunian object, a Kuiper (pronounced K-Eye-Per) Belt object, and many other names. None of these are strictly “Planet” because the definition of a planet varies. The question of “What is a planet” is three fold. The object must orbit around the Sun (it’s parent star), The object must be rounded by its own gravity, and it must have cleared its orbital path of debris. Pluto does two of these three things. Since its neighborhood is the Kuiper Belt, it has not cleared its path of debris. There’s potentially millions of “Trans-Neptunian Objects” in the Kuiper Belt, and because of that, Pluto was classified as a Dwarf Planet. In the event that it suddenly clears its path, and survives, the IAU may promote it once again, but that’ll be in a few billion years.
Are we landing on Pluto? Why? Why not?
The short answer is, No. The reason is because our Solar System is far too big. One of my favourite quotes from Vlad the Astrophysicist, a friend of Peter Mulvey, “Space is too large, Time is too short”. Remember, Pluto is almost 9.65 BILLION kilometers from Earth, whereas Earth is only 93 million kilometers from the Sun. Since the human brain has difficulty rationalizing such large numbers, think of it this way: A million seconds is about 11.5 days. A billion seconds is about 31.75 years. A trillion seconds is just under 32 centuries! The reason why we’re not orbiting Pluto is because in order to get too Pluto within a decent time, we needed to make New Horizons very lightweight, and launch it at very high speed (almost 14 km/s). The weight of the probe would’ve been significantly heavier to account for weight of fuel to slow the probe down and insert it into orbit; and even more heavier to land it properly. On top of all of this, it takes light and radio waves (how we’d communicate with a probe to, for example, move it forward, give it coordinates to travel to, activate a camera, etc.) 265.4 minutes.. just under 4.5 hours, and that’s one way.
What do we know about Pluto thanks to New Horizons?
Pluto is almost double the diameter we originally thought, at 2370 km! It was previously thought to be only 1151 km. This size now makes Pluto the largest known Kuiper Belt object (Trans-Neptunian Object). We know that it has an atmosphere – a thin one, but it’s something. We don’t yet know exactly what it’s made of, but we have guesses. Due to the increase in mass and measurements, we know it’s less dense than previously thought – this means that there’s more ice than previously thought. Here’s an approximation of the relative size of Earth and Pluto, and Pluto’s largest moon, Charon.
What does Pluto look like?
Previously, the best images we had of Pluto was this: (Taken by Hubble circa ~2003)
We now know it looks like this: (REAL COLOUR!!)
And here, just for S&G’s, is an artist’s conception of Pluto:
So what happens afterwards? Is New Horizons coming back? Why? Why not?
New Horizons left Earth and will never come back. The same reasoning behind why we’re not orbiting Pluto (weight, time, etc.), is the same reasoning behind why it will never come back. We would’ve needed to put much more additional fuel to slow it right down to a stop and then send it back to us. We’d also need to plot a course (TO THE QO’NOS SYSTEM, WARP 9, ENGAGE!!).. uhh.. sorry.. force of habit.. We’d also need to plot a course back to Earth, and have even more fuel to slow it down once it got here so we could scoop it up. It’s just not feasible. New Horizons has other missions planned after it’s out of range of Pluto, and that’s to go check out other TNO’s in the Kuiper Belt. Nothing is officially planned, only strongly suggested. I will post another article on my site once official announcements are made. The New Horizons mission will be officially over, assuming no mission extensions are granted, in 2026. At that time, it will be approximately 100 AU from the Sun (just under 15 billion kilometers).