What is a Lagrange point?
In 1772, mathematician Josue Louis Lagrange calculated in his study "The Problem
Jose Louis Lagrange
There are five Lagrange points in total - L1, L2,L3, L4 and L5. For scientists, the most interesting points to study are the points L4 and L5 - the only stable regions of all the Lagrange points. If the satellite hits L1 or L2, after a few months the orbits will change and the area of no gravity will also shift, so the space body will have to perform various maneuvers to stay in this area.
Points L4 and L5, which are considered the moststable, located on the plane of the Earth's orbit at a distance of 150 million km from our planet (for comparison, the distance from the Earth to the Moon is 383.4 thousand km, the average distance to Venus is from 38 to 250 million km, depending on the location of the planets). In this case, L4 rotates around the Sun 60 ° ahead of the Earth, and L5 - 60 ° behind.
Scientists around other planets in the solar systemsimilar areas are also observed. In 1906, astronomer and astrophotography pioneer Maximilian Wolf discovered an asteroid that was constantly in the same place beyond the main asteroid belt between the orbits of Mars and Jupiter.
This asteroid turned out to be Jupiter's L4 point.Scientists named it Achilles - it was from him that the tradition of naming all such asteroids by the names of participants in the Trojan War began. Now, thanks to this discovery, astrophysicists have discovered more than a thousand asteroids located at two stable Lagrange points of Jupiter.
Orbit of asteroid Achilles
Another thing is that the search for such asteroidsaround other planets have not yet been so successful: they have not yet been found near Saturn, and only one near Neptune. Probably, until astrophysicists simply did not calculate the correct location of these areas for such planets.
HM. It's still not very clear how it works.
A Lagrange point is a place in space wherethe combined gravitational forces of two very massive bodies—the Earth and the Sun or the Earth and the Moon—are equal to the centrifugal force felt by a much smaller third body. The interaction of these forces creates an equilibrium point where a conventional spacecraft can be “parked” forever for carrying out observations.
Suppose we have two very large objectsin space - the Earth and the Sun. They have a gravitational pull. And there is a satellite - if we launch it too close to the Sun, then gradually gravity will pull it towards the star, and it will either crash into it or enter the solar orbit. If to the Earth, then the satellite will either end up in near-Earth orbit, or enter the atmosphere of our planet and burn up in it.
Lagrange points are places in space where gravitytwo objects (in our case the Sun and the Earth) effectively cancel each other out. This will allow the satellite to stay exactly where it was launched.
Lagrange points
Mathematics works in such a way that the points L1, L2, and L3are not stable. For some time, our satellite, which ended up at these points, will be inside the regions, but then the gravity will still change and our cosmic body will fly further. This can be compared to a piece of marble that we have carefully placed on top of an inverted bowl. He will lie there, but one blow on the table - and the marble will roll down.
L4 and L5 are stable.Even if your companion didn't get to these points perfectly, gravity will sort of push it into position anyway so that it stays there forever. This time, our marble piece is already at the bottom of the bowl moving quickly to the right, so even if it's not perfectly centered, it will move to the correct position.
Okay. How can Lagrange points be used?
Space researchers back in the 1970syears, they paid attention to Lagrange points. For example, a space solar observatory could be placed at point L1 of the Earth-Sun system. It will never fall into the shadow of the Earth, therefore, observations can be carried out without interruption.
Point L2 of the "Earth-Sun" system can bealmost ideal for installing a space telescope in it. In it, the Earth almost always obscures the sunlight and does not reflect it to this place, which would allow scientists to constantly study other stars.
At point L1 of the "Earth-Moon" system, one can placerelay station during the exploration of the Earth's satellite. The station will be constantly in line of sight for most of the hemisphere of the Moon facing the Earth. Therefore, to communicate with it, the future colonists of the Moon will need transmitters ten times less powerful than those for communication with the Earth.
There are many projects in which astrophysicists plan to use Lagrange points in one way or another in their research.
ISEE-3 is the first spacecraft launched inpoint L1 of the "Earth-Sun" system. It was launched back in 1978, as part of the mission, it was supposed to prove that the existence of these libration points (another name for the Lagrange points is High-Tech) is generally real, and also to explore the upper boundaries of the Earth's magnetosphere, passing just at a distance of about 1.5 million km from our planet. After that, ten years later, the probe was sent to comets Halley and Giacobini-Zinner. Now ISEE-3 has been sitting in space for several decades in the off state.
At point L1 of the Earth-Sun system nowThere are several missions, including the solar wind probe GGS Wind, the heliosphere station SOHO and DSCOVR to analyze coronal mass ejections.
At point L2 of the "Earth-Sun" system, for a long timethere was a WMAP satellite to study the cosmic microwave background radiation that arose during the Big Bang (now, after the completion of the mission, it has been sent to the burial orbit), the Herschel space observatory, the Planck space observatory, the Gaia space telescope. In the future, one of the most important projects in space exploration will be launched here - the James Webby Telescope in 2024, which will replace the iconic Hubble.
Moreover, all these objects, of course, arenot at one point, but on halo orbits around the Lagrange regions. There are quite a lot of them - despite the fact that the probes must have stabilizing equipment that allows them to stay on them for a long time.
Why, then, are they not going to build colonies on these points?
They're getting ready.There are several projects to create colonies at Lagrangian points, and there are even public associations that popularize this idea - L5 Society, Republic of Lagrangia and National Space Society. The most famous proponent of creating a colony-settlement of humanity at Lagrange points is considered to be astrophysicist Gerard O’Neill, who presented the concept of “Island III” - a space station located at one stable point.
Island III
However, these theories have some serioustechnical difficulties: the negative impact of solar wind and other cosmic rays on the human body. In addition, all Lagrange points are subject to the still poorly studied influence of plasma in the equatorial plane of the Earth's magnetosphere. In this regard, all settlements that will be located at these points must be protected from cosmic radiation.
In addition, due to the lack of gravitypermanent space settlements at Lagrange points should be equipped with technologies to create its artificial counterpart. At the same time, such technologies do not exist today.
Well, the most important thing.While all theories on the creation of colonies on other planets are hypothetical, for their appearance, humanity still needs to make a huge number of discoveries. You can read the history of the race to create bases on the Moon and Mars here, here and here.
OK. But I have seen that Lagrange points can also be used for alien observation of the Earth!
They can. In science fiction, the theory is very developed that aliens build their space stations at points where there is no gravity, and observe the Earth from them.
On the one hand, some Lagrange pointsespecially in the Earth-Sun system, it is quite difficult to study, since they are too close to the Sun (and sometimes behind it). Therefore, theoretically, any station can be located there.
On the other hand, this theory remains only in science fiction, because, as we have long known, the existence of aliens has not yet been proven by anyone.