Astronomers doubt that there is an undiscovered 9th planet in our solar system

(ORDO NEWS) — Planet Nine is a theoretical undetected giant planet in the mysterious distant corners of our solar system.

It is assumed that the presence of planet 9 explains everything: from the tilt of the axis of rotation of the Sun to the apparent accumulation of small icy asteroids outside Neptune in orbits. But does planet nine actually exist?

Discoveries at the edge of our solar system

The Kuiper Belt is a collection of small ice bodies that rotate around the Sun outside Neptune at distances exceeding 30 AU (one astronomical unit or AE is the distance between the Earth and the Sun). These Kuiper Belt objects (KBO – Kuiper Belt objects) range in size from large boulders to 2,000 km across. In the Kuiper belt, there are remnants of planetary material that have never been included in any planet, like the asteroid belt.

The most successful study of the Kuiper belt to date is the OSSOS program, which offers a more cunning explanation of the orbits that we see. It has been found that many of these objects have very elliptical and inclined orbits, such as Pluto.

Mathematical calculations and detailed computer simulations showed that the orbits that we see in the Kuiper belt could only be created if Neptune initially formed a few AE closer to the Sun, and then migrated out into its current orbit. Neptune’s migration explains the abundance of highly elliptical orbits in the Kuiper belt and can explain all the orbits of Kuiper belt objects that we observe, with the exception of a few objects in extreme orbits, which always remain at least 10 AU. outside of Neptune.

According to theory, the planet nine is five to ten times more massive than the Earth, and its orbit ranges from 300-700 AS. Several predictions were published regarding its location in the solar system, but none of the search groups have so far found it. After more than four years of searching, there is still only indirect evidence in favor of the ninth planet.

Search for objects in the Kuiper belt

Search requires careful planning, accurate calculations, and close monitoring. The OSSOS mission is a collaboration of 40 astronomers from eight countries. They used the Canadian-French-Hawaiian telescope for five years to detect and track more than 800 new objects in the Kuiper belt, nearly doubling the number of known objects with well-measured orbits. Objects detected by OSSOS range in size from several kilometers to more than 100 km, and the detection distance is from several AEs to more than 100 AEs, most of which are located in 40-42 AEs in the Kuiper main belt.

The objects of this belt do not emit their own light: these small ice bodies only reflect the light of the sun. Thus, the prejudices against detection at large distances are extreme: if you move an object 10 times further, it will become 10,000 times weaker. And due to the laws of physics, objects in the Kuiper belt in elliptical orbits will spend most of their time in the most remote parts of their orbits. Thus, it is easy to find objects in elliptical orbits when they are close to the Sun and bright, but these objects spend most of the time being much weaker and more difficult to detect.

This means that objects in elliptical orbits are especially difficult to detect when they are relatively far from the sun. To date, only a few of them have been found, and with the help of modern telescopes, we can only detect them when they are near the pericenter – the closest point to the Sun in its orbit.

This leads to a bias in observations, which has historically been ignored by many studies of the Kuiper belt: objects in each part of the solar system can only be detected at certain times of the year. Terrestrial telescopes are additionally limited by seasonal weather, and discoveries are less likely to occur during periods when cloudy, rainy or windy conditions dominate the planet. Discoveries are also much less likely near the plane of the Milky Way galaxy, where countless stars make it difficult to find faint, icy wanderers in the pictures.


OSSOS discovered several new extreme objects in the Kuiper belt, half of which are outside a limited area and are statistically consistent with a uniform distribution.

All extreme objects discovered before the advent of OSSOS were found as a result of studies that did not fully describe their orientation. We carried out additional modeling, which showed that if observations are made only in one season from one telescope, then the extreme Kuiper belt objects will naturally be detected in only one quadrant of the solar system.

Further, checking the theory of planet nine, we examined in detail the orbits of all known “extreme” objects and found that all but two objects with a pericenter can be explained by known physical effects. These two Kuiper belt objects are extreme, but our previous detailed computer simulation of the Kuiper belt, which included gravitational effects from planet nine, made it possible to obtain a set of the same “extreme” objects with pericenters smoothly varying from 40 to more than 100 AE.

This simulation predicts that there should be many belt objects with pericenters equal to the two found, but also many objects with smaller pericenters, which should be much easier to detect. Why do orbit openings fail to predict? The answer may be that the theory of planet nine is not supported by our observations.

Our observations with careful research found objects that are not connected with planet nine, and our simulation shows that the Kuiper belt must have orbits of objects different from those that we observe – if planet nine exists. Other theories should be used to explain extreme objects with a high pericenter, but there is no shortage of proposed theories in the scientific literature.

We have yet to discover many beautiful and amazing objects in the mysterious outer solar system, but research does not confirm that planet nine is one of these objects.


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