Will Pluto become a planet again?

Why isn't Pluto a planet anymore?

In 1978, one of Pluto's satellites, Heron, was discovered. In addition to the fact that Heron is only 8 times lighter than Pluto, Heron does not revolve around Pluto, but both celestial bodies revolve around a common point of mass. In addition, Pluto's situation was exacerbated by the discovery in 2005 of Eris -- another dwarf planet that is also heavier than Pluto.

Dilemma

The scientific community is now faced with the question of whether to admit Eris as a planet and risk increasing the list of planets, or whether to remove Pluto from the list of planets altogether and draw up a complete definition of a planet as such

So what is a planet?

So, in 2006, the second option was chosen -- to exclude Pluto from the list of Planets and make a definition of a complete planet as such.

There are only 3 factors for defining a planet:

1. This body revolves around the Sun.
A very logical rule that excludes the Moon, Ganymede, and other planetary satellites. That would be all right, but Pluto revolves around the sun.

2. It's massive enough to have a spherical shape under its own gravity.
Pluto doesn't have a problem here either, just like the moon.

3. This body has "space free of other bodies" near its orbit.
This is where the controversy arises: the body must have enough mass to dominate, turning all objects in its orbit into satellites.

It's just Pluto's third point that's screwed up. As written before -- Pluto and Heron are orbiting around a common mass point, hence the orbit is not cleared. And that's how all objects like Eris and Pluto became dwarf planets.

Well, if there's no doubt about it, what's the point?

I am in no way going to challenge the decision made in 2006, I just want to say that science has advanced since 2006 and make some arguments in favor of the planet Pluto.

1. Pluto's atmosphere.

Pluto is incredibly far away from us. It seems to be completely lifeless. However we think it is, in 2015 the New Horizons probe sent a photo of a sunset on Pluto. Everyone was surprised to see 20 layers of atmosphere rising 1,600 kilometers (Even higher than on Earth!). In fact, Pluto is the only transneptunian object that has its own atmosphere.

Pluto's atmosphere is 100,000 times weaker than Earth's, and it consists mostly of nitrogen. Yes, it certainly doesn't inspire much hope, but the very fact of its presence makes it stand out from the other candidates.

What is even more interesting, Pluto constantly replenishes the atmosphere with fresh nitrogen, hence there are unknown processes going on inside, synthesizing nitrogen on Pluto's surface.

2. Geological activity.

We all (or almost all) imagine Pluto's surface as dead, lifeless, dotted with craters. That's what Erida looks like, Ceres -- the typical landscape of a dwarf planet. But the photos sent by New Horizons literally say the opposite: Pluto has a huge number of mountain ranges, deep depressions, canyons and there are all signs of geological activity. And some mountains are up to 3 kilometers high! This indicates that at least 100 million years ago Pluto was geologically active. Even Mars, our neighbor, stopped being geologically active a long time ago.

Of course, all these processes require energy. Lots of energy. On earth, these processes are achieved by a hot core. And for Pluto and sunlight plays almost no role.

According to New Horizons data, it is likely that a liquid ocean exists beneath the crust of frozen nitrogen and rocky surface -- a better explanation for the cracks on Pluto's surface.

Some scientists believe that depending on the season, the liquid ocean freezes and then becomes liquid again, literally "tearing up" the planet. Some believe there is
cryovolcano on Pluto.

3. Is rule 3 wrong?

Meet Philip Metzger -- Pluto's unofficial "advocate", a planetary scientist at the University of Central Florida (USA). In a new study published in the journal Icarus, Philip reports that this standard (orbital clearance) of planet classification is not supported by the research literature.

Philip Metzger reviewed scientific writings over the past 200 years and found only one publication since 1802 that used the criterion of orbital purity to classify planets and was based on irrefutable reasoning. Moreover, satellites such as Titan at Saturn and Europa at Jupiter have been regularly referred to by planetary scientists since Galileo's time as planets.

"The IAU definition shows that the fundamental object of planetary science, the planet, is defined on the basis of a concept that no one uses in their research. And it leaves out the second most complex and interesting planet in the solar system. "We have a list of more than 100 examples of planetary scientists who use the word 'planet' differently than the official definition requires, but they do so because it is functionally useful," says Philip Metzger.

The scientist's opinion is reinforced by the sloppiness of the definition. The International Astronomical Union did not specify what exactly is meant by "orbital clearance." If you look at it literally, there are no planets at all, because none of them can completely and permanently clear their orbit.

A most excellent deduction.

The Pluto-Heron system satisfies the definition of a double planet. It is currently the only pair of bodies in the solar system that can claim such status. From the discovery of Pluto in 1930 until 1978, Pluto and Heron were considered to be one and the same celestial body.

It's a bit odd to deny all small planets the right to be called planets. Even looking at it this way, Jupiter also affects the Sun and the center of mass is beyond the star's limits. So what, now do we exclude the Sun from the list of stars just because Jupiter influences it too?) Of course not. The scientists who made the decision about Pluto in 2006 are understandable -- and some kind of decision was needed. We have no problem with giant planets like Jupiter or Saturn, but with smaller ones, there are hiccups.