The Oort Cloud. The limits of the Solar System

The Oort Cloud, also known as the «Öpik-Oort cloud», is a hypothetical spherical cloud of trans-Neptunian objects. It could not be observed directly. It is located at the limits of our solar system. And with a size of 1 light year, it is a quarter of the distance from our closest star to our solar system, Proxima Centauri. To get an idea of ​​its size with respect to the Sun, we are going to detail some data.

We have Mercury, Venus, Earth, and Mars, in that order, relative to the Sun. A ray of sunlight takes 8 minutes and 19 seconds to reach Earth's surface. Further on, between Mars and Jupiter, we find the asteroid belt. Following this belt are the four gas giants: Jupiter, Saturn, Uranus, and Neptune. Neptune is approximately 4 times as far from the Sun as Earth is. Sunlight takes approximately 30 hours and 4 minutes to reach Earth. If we consider our farthest planet from the Sun, The confines of the Oort Cloud would be 2.060 times the distance from the Sun to NeptuneThis highlights the importance of the Oort Cloud and its effects on the Solar System.

Where is its existence deduced from?

In 1932, the astronomer Erns Öpik, he postulated that comets orbiting for long periods originated within a large cloud beyond the confines of the solar system. In 1950 the astronomer Jan Oort, He independently postulated the theory, resulting in a paradox. Jan Oort claimed that meteorites could not have formed in their current orbit due to the astronomical phenomena that govern them, so he argued that their orbits and all of them must be stored in a large cloud. This colossal cloud is named after these two great astronomers.

Oort investigated between two types of comets. Those with an orbit less than 10 AU and those with long-period orbits (almost isotropic), which are greater than 1.000 AU, even reaching 20.000. In addition, he saw how they all came from all directions. This allowed him to deduce that, if they came from all directions, the hypothetical cloud should have a spherical shape. To better understand how they form, you can consult more information about the comets of the solar system.

What exists and does the Oort Cloud encompass?

According to the hypotheses of origin of the Oort Cloud, is in the formation of our solar system, and the large collisions that occurred and the materials that were thrown out. The objects that make up the planets formed very close to the Sun in their early days. However, the gravitational pull of the giant planets also distorted their orbits, sending them to the distant points where they are located.

Within the Oort cloud, we can differentiate two parts:

1. Internal / Indoor Oort Cloud: It is more gravitationally related to the Sun. Also called the Hills Cloud, it is shaped like a disk. It measures between 2.000 and 20.000 AU.
2. Oort Cloud Outer: Spherical in shape, more related to the other stars and the galactic tide, which modifies the orbits of the planets making them more circular. Measures between 20.000 and 50.000 AU. It should be added that it is really the gravitational limit of the Sun.

The Oort Cloud as a whole encompasses all the planets in our solar system, dwarf planets, meteorites, comets, and even trillions of celestial bodies larger than 1,3 km in diameter. Despite such a significant number of celestial bodies, the distance between them is estimated to be tens of millions of kilometers. The total mass it would have is unknown, but making an approximation, having as a prototype Halley's Comet, It has been estimated at about 3 × 10 ^ 25kg, that is, about 5 times that of planet Earth. For more information about this famous comet, you can see Halley's Comet and its importance.

The Tidal effect in the Oort Cloud and on Earth

In the same way that the Moon exerts a force on the seas, raising the tide, it has been deduced that Galactically this phenomenon occursThe distance between one body and another reduces the gravitational force that each exerts on the other. To understand the phenomenon being described, we can look at the force that the Moon's and Sun's gravity exert on Earth. Depending on the Moon's position relative to the Sun and our planet, tides can vary in magnitude. An alignment with the Sun exerts such a strong gravitational force on our planet that it explains why tides rise so much.

In the case of the Oort Cloud, let's say that it represents the seas of our planet. AND the Milky Way would come to represent the Moon. That's the tidal effect. What it produces, as the graphic description suggests, is a deformation toward the center of our galaxy. Considering that the Sun's gravitational pull becomes weaker the further we move from it, this small force is also sufficient to disturb the motion of some celestial bodies, causing them to be sent back toward the Sun. For more information on the tidal effect on celestial bodies, see the tidal effect.

Cycles of extinction of species on our planet

Something that scientists have been able to verify is that approximately every 26 million yearsThere is a repeating pattern. It involves the extinction of a considerable number of species during these periods. Although the exact reason for this phenomenon cannot be definitively stated. The tidal effect of the Milky Way on the Oort cloud it could be a hypothesis to consider.

If we consider that the Sun revolves around the Galaxy, and in its orbit tends to pass through the "galactic plane" with a certain regularity, these extinction cycles could be described. It has been calculated that every 20 to 25 million years, the Sun passes through the galactic plane. When this happens, the gravitational force exerted by the galactic plane would be sufficient to disturb the entire Oort Cloud. Considering that it would shake and disturb the member bodies within the Cloud, many of them would be pushed back towards the Sun, which could have devastating effects on our planet, similar to what is discussed in the theory of panspermia.

Alternative Theory

Other astronomers consider that the Sun is already close enough to this galactic plane. And the considerations they bring is that the disturbance could come from the spiral arms of the galaxy. It is true that there are many molecular clouds, but also they are riddled with blue giants. They are very large stars and they also have a very short life span, as they quickly consume their nuclear fuel. Every few million years some blue giants explode, causing supernovae. That would explain the strong shaking that would affect the Oort Cloud.

Be that as it may, we may not be able to perceive it with the naked eye. But our planet is still a grain of sand in infinity. From the Moon to our galaxy, they have affected from their origin, the life and existence that our planet has endured. A huge amount of things are happening right now, beyond what we can see.