Where did the last ice ages come from? The answer is in space

When we imagine the movement of celestial bodies in space, we usually think of a fixed sun around which eight planets revolve. Behind the four rocky planets we find the asteroid belt, behind which four giant gas planets orbit. Of course, there are still moons orbiting six of these eight planets, and comets appear here and there. Those more interested in astronomy also know about the Kuiper Belt, which extends beyond the gaseous planets and contains dwarf planets like Pluto. However, this is only the beginning of the whole story.

We forget that the solar system described in some detail above is not a fixed entity, and revolves with 400 billion other stars around the center of our galaxy, the Milky Way. In its journey around the supermassive black hole Sagittarius A*, the Sun and its planets approach and then move away from other stars. From time to time, our planetary system encounters gas clouds in its path.

Read also: No, the sun is not the center of the solar system. This is the place next to it

It is worth emphasizing here that the Sun and its planets enter what is called the heliosphere, which is the region dominated by the solar wind, which is a continuous stream of high-energy particles emanating from the Sun and reaching beyond the Kuiper Belt. Throughout this region, interplanetary space is dominated by these solar winds, which essentially protect it from the influence of interstellar space, which is governed by radiation from other stars, high-energy cosmic rays, and the debris of stars that eventually explode. From their lives as supernovae traveling through interstellar space.

As the solar system moves through interstellar space, it strikes this environment from the front with the edge of its heliosphere. This solar wind field is the first to expand into the interstellar medium, protecting all the planets in our system.

You have it Latest scientific works Published in the journal Nature astronomy Astronomers from Boston University and the Ratcliffe Institute at Harvard University point to a very important event that occurred in the entire solar system only 2-3 million years ago. Given that dinosaurs did not set foot on Earth for 65 million years, this event occurred relatively recently, when the first ancestors of modern humans were already on Earth.

By analyzing the motion of the solar system in interstellar space based on data from the Gaia Observatory, which studies the positions, motions and velocities of more than 1.5 billion stars in our environment, scientists discovered that our planetary system collided with a cloud of cold hydrogen gas that belonged to the so-called local cloud lynx. Cold (LLCC). Because this cloud was denser than the surrounding environment in which the solar system previously existed, the front of our heliosphere was distorted. The outer edge of the solar wind-dominated protective field has been pushed into the center of the solar system, like the hood of a car hitting a wall of water.

As a result, Earth found itself outside the heliosphere and exposed to frozen interstellar space. It so happened that, among other things, during this time, a series of ice clusters appeared on Earth, which – as it turned out – were probably caused by exposure to the cold interstellar space.

Read also: This giant bubble protects us from cosmic radiation. The heliosphere reveals another mystery

Furthermore, since Earth was outside the heliosphere, it was not protected against cosmic rays and atoms from supernova explosions, especially heavy elements that originate inside massive stars. The geological record seems to support this theory, as the fossil record of this period shows a marked increase in the number of iron-60 and plutonium-244 atoms.

It is not known how long the Earth remained outside the heliosphere. It could be several hundred or a million years. It all depends on the size of that part of LLCC through which the solar system passed. This does not change the fact that after passing through it, the ocean became thinner again and the front of the heliosphere returned to its place.

Scientists suspect that this was certainly neither the first nor the last case of collision with a cloud of cold hydrogen in the history of the solar system. Therefore, we have another factor to consider in studies of climate change on Earth over the ages. Now it would be good to look ahead and determine when the Earth will have the opportunity to enter a dense gas cloud again. Just in case, it would be good to know when it might get cold again on Earth.