The hunt for the ninth planet: what is it made of?

The hunt for the ninth planet: what is it made of?

The most exciting thing about astronomy is to peer into the unknown and discover something new in the deep cosmic abyss. But when hints of “something new” appear on our cosmic threshold, global excitement becomes noticeable.

I, of course, refer to the “ninth planet of the solar system” - a hypothetical world that seems to cause gravitational resonance in the frozen barren lands of our outer part of the solar system beyond the orbit of Pluto.

In January, Californian Institute of Technology astronomers Mike Brown and Konstantin Batygin announced the opening of a group of objects in the Kuiper belt. It turned out that outside the orbit of Pluto is a strange orbit. The Kuiper belt and the oddities often go hand in hand, but in this case, the movement of these small objects hinted at another mysterious object, located further away, which may have a gravitational effect on these MICs (Kuiper belt objects) creating your strange synchronicity.

The search for planets in the outer solar system is difficult. Although we have powerful observatories that can see the smallest details in galaxies millions of light-years distant from Earth and survey telescopes that can accurately detect small asteroids when they rush through the inner part of the solar system, the outer solar system remains one of the most interesting, but largely unexplored areas in local space. If a moderately sized planet is located in an orbit far enough from the Sun, it may still be too small and too cold to be seen during the surveys. If it cannot be detected with reviews, more powerful telescopes will not know where to look. But even then, these distant planets would be slightly larger than a point in the ocean of stars. Space, after all, is a great and planetary discovery that requires a combination of skill, precision instrument making and good luck. In the case of the ninth planet, its presence is still trying to prove when searching. As well as the discovery of Neptune in 1846, this movement of other objects in the solar system may hint at its gravitational dominance in the region. Now astronomers are becoming even more creative and are exploring the trajectory of the NASA New Horizons mission in the hope of seeing any unreported drift (shift) from its planned path through the Kuiper belts, which can also signal the gravity of the ninth planet.

At the same time, scientists from the University of Bern, Switzerland, moved one step ahead of these exciting early hints to a new planet, and put some restrictions on how big it is and how “warm” the object can actually be. Their study was accepted for publication in the journal Astronomy & Astrophysics.

Of the models of Brown and Batygin, the ninth planet should have a high elliptical orbit, not approach closer than 200 a. e. (this is 200 times the distance from the Earth to the Sun, and 4 times the distance between Pluto and the Sun) and expands to 1200 a. e. In short, it would be an extreme world far beyond the borders of our “classical” Solar System and even beyond the most distant object of the Solar System, known today as dwarf planet Eris (almost 100 A. e.). Eris was also discovered by Brown in 2005. This discovery, which ultimately led to the reclassification of Pluto.

Without accurate data in infrared surveys, Bern’s astronomers Christophe Mordasini and doctoral student candidate Esther Linder intended to decipher more of the ninth planet’s characteristics using well-known planetary evolution models that they apply to the formation of planets orbiting other stars. These worlds are also known as exoplanets. These modeling processes could be used to screen survey data. Perhaps this will help open an object that went unnoticed in the night sky. Brown and Batygin were able to estimate the mass of the ninth planet, based on the gravitational influence that it seems to have. This is most likely a significant sized planet, about 10 times the mass of the Earth. And this, perhaps, makes it a “mini-Uranus”. As a world, it is a place with a solid core and a cold, dense layer of gas.

Knowing that the ninth planet has yet to be seen using infrared surveys (such as the Wide-Angle Infrared Survey Explorer or WISE), the researchers already assume the upper limit of the physical size of the ninth planite and know its approximate mass, distance from the Sun, and the use of a planetary formation model. Thanks to this, Mordasini and Linder were able to form an idea of ​​what the temperature and size of the planet is.

According to their calculations, the ninth planet should have a radius of 3, 7 times the Earth and the upper temperature of the atmosphere -226 degrees Celsius (or 47 degrees Kelvin). They came to these numbers, considering the predicted orbit of the ninth planet around the sun and the age of our solar system. The hypothetical world would have been formed from the protoplanetary disk of our Sun, which began to condense on the planet about 4, 6 billion years ago.

At such staggering distances from the Sun, it is no surprise that the predicted temperature on a ninth planet would be very cold. But it is still warmer than one would expect from a lone individual heated by sunlight. After the formation of planets, the gravitational energy in their cores can hold their molten, hot “entrails” for billions of years. This high temperature, however, is slowly dispersed and can be seen with highly sensitive infrared telescopes. Thus, the temperature at 47 degrees Kelvin ninth planet "means that the planetary radiation dominates cooling its core, otherwise the temperature will be only 10 degrees Kelvin," - said Linder in a press release. “Its internal strength is about 1000 times greater than its absorbed power.” This means that the reflected sunlight will be negligible compared to the internal heat in the world currently generated, which makes the planet's infrared signal much more powerful than the search for reflected sunlight in the optical wavelength range. This may seem like an obvious conclusion for astronomers looking for ice objects far from the sun. But it is still an incredible idea that the ninth planet is the hottest object in the depths of the country of the solar system, despite having only 47 degrees above absolute zero. In astronomy, “heat” is a very relative concept.

Knowing only a few clues about the nature of the ninth planet, it is very interesting to look at how this hypothetical world is formed. “With the help of our research, the candidate for the ninth planet is now more than a simple point mass. It takes shape and physical properties, ”said Mordasini.

Currently, astronomers are using Brown and Batygin's observation models to track the possible location of the ninth planet, but it will be difficult to see the world using infrared data that are now available to us.

What will the ninth planet look like? Apparently, we will have to wait until the Large Synoptic Survey Telescope is completed near Cerro Tololo in Chile before we catch the planet’s weak signal. Only then will we be able to decisively prove that there is a world there and we will understand what it is: a small gaseous planet, or something else. At the same time, theoretical studies will help to make assumptions of what the planet consists of.

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