2nd satellite of the earth. The Moon is not the only satellite of our planet. Rotation of the Moon around the Earth
The Moon is the only natural satellite of the Earth. We were once so sure of this that we didn’t even give our moon a specific name. On the other hand, this is completely justified, because The Moon, being the brightest and largest object in the night sky, needs no further introduction. The remaining 6 satellites of the Earth are so small and distant that they can only be seen through powerful telescopes. In addition, they revolve around the Sun, but are influenced by the Earth's gravity.
One can argue for a long time about whether such objects are natural satellites, but since, so to speak, the official point of view on this matter has not yet been determined, then nothing prohibits classifying them as such. The International Astronomical Union, the leading organization in determining what a particular celestial body is and how this body should be correctly called, promises in the near future to give a clear definition of the concepts of “satellite” and “component of the gravitational system.” Therefore, for now we have this, we have it.
So, together with the Moon, the Earth has 7 satellites. 5 of them are quasi-orbital asteroids or simply quasi-satellites, another one belongs to the class of Trojan asteroids. Up to a certain point, both of them (in in this case other) were quite ordinary asteroids and rotated in their more or less stable orbits around the Sun, until one day they ran into a huge Earth, relative to their dimensions, as a result of which they fell into a 1:1 orbital resonance with the latter. In other words, the rotation of the Earth and the “captured” asteroids has been synchronized and now they make one revolution around the Sun in the same amount of time.
Otherwise, these two types are fundamentally different from each other, so we will consider each separately.
Quasi-satellites of the Earth
What is a quasi-satellite? In principle, it can become almost any celestial body that finds itself in a 1 to 1 orbital resonance with the planet. Despite completely coinciding orbital periods, quasi-satellites always have a greater eccentricity (the degree of deviation from the circle) of the orbit, and sometimes also a pronounced inclination relative to the ecliptic plane (the plane in which the planet rotates).
The main feature of quasi-satellites, as well as Trojan asteroids, is that at any given time they are exactly the same distance from the Earth as they were a year ago. Actually, for this reason they are considered natural satellites.
On the other hand, their “loyalty” to the planet is not always stable: the duration of the gravitational tandem can range from several orbital periods to hundreds of thousands of orbits.
Cruithney
The largest and most famous among the Earth's quasi-orbital satellites is an asteroid Cruithney (3753). It was discovered back in 1986 by an amateur astronomer and became the first known celestial body in the solar system to move in such a strange but stable orbit. Later, astronomers discovered similar companions to Venus, Jupiter, Saturn, Uranus, Neptune and even Pluto.
Unfortunately, we don’t really know what Cruitney is. This is an asteroid with a diameter of about 5 km. It rotates in a very elongated orbit inclined to the plane of the ecliptic, the perihelion (the point of the orbit closest to the Sun) lies between the orbits of Mercury and Venus, and the aphelion - between Mars and Jupiter.
Humanity has only just learned that the Earth has another satellite besides the Moon.
The second satellite of the Earth, astronomers say, differs from the big Moon in that it completes a full revolution around the Earth in 789 years. Its orbit is shaped like a horseshoe, and is located at a distance comparable to the distance from Earth to Mars. The satellite cannot approach our planet closer than 30 million kilometers, which is 30 times further than the distance to the Moon.
Relative motion Earth and Cruithne in their orbits.
Scientists say that the Earth's second natural satellite is the near-Earth asteroid Cruithney. Its peculiarity is that it intersects the orbits of three planets: Earth, Mars and Venus.
The diameter of the second Moon is only five kilometers, and this natural satellite of our planet will come to its closest distance to Earth in two thousand years. At the same time, scientists do not expect a collision between the Earth and Cruithne, which has approached our planet.
The satellite will pass from the planet at a distance of 406,385 kilometers. At this moment, the Moon will be located in the constellation Leo. Our planet's satellite will be fully visible, but the size of the Moon will be 13 percent smaller than at the time of its closest approach to the Earth. A collision is not predicted: the earth's orbit does not intersect anywhere with Cruithney's orbit, since the latter is in a different orbital plane and is inclined to earth's orbit at an angle of 19.8°.
Also, according to experts, in 7899 years our second moon will pass very close to Venus and there is a possibility that Venus will attract it to itself and thereby we will lose “Cruithney”.
The new moon Cruithney was discovered on October 10, 1986 by British amateur astronomer Duncan Waldron. Duncan spotted it in a photograph from the Schmidt telescope. From 1994 to 2015, the maximum annual approach of this asteroid to the Earth occurs in November.
Due to the very large eccentricity, the orbital speed this asteroid changes much more strongly than that of the Earth, so from the point of view of an observer on Earth, if we take the Earth as a reference system and consider it stationary, it turns out that not the asteroid, but its orbit rotates around the Sun, while the asteroid itself begins to describe ahead of the Earth a horseshoe-shaped trajectory, reminiscent of a “bean” in shape, with a period equal to the period of revolution of the asteroid around the Sun - 364 days.
Cruithne will approach Earth again in June 2292. The asteroid will make a series of annual approaches to the Earth at a distance of 12.5 million km, as a result of which there will be a gravitational exchange of orbital energy between the Earth and the asteroid, which will lead to a change in the orbit of the asteroid and Cruitney will again begin to migrate from the Earth, but this time in the other direction , - it will lag behind the Earth.
On September 9, 2018, not all people in the world, but most likely very many, watched the live broadcast of the passage of asteroid 2018 RC past the Earth, which passed from us at a record close distance of 1/2 the distance to the Moon.
The asteroid did not fall into the Atlantic and seemed to fly on, assuring the audience of a stable tomorrow. But in reality, as one lady told her twin sister's husband, sometimes things are not what they seem.
In 2016, NASA miraculously discovered one small asteroid, named 2016 HO3. This is a small space pebble, the size of which is 35 X 90 meters, that is, asteroid 2016 HO3 is almost complete analogue asteroid 2018 RC.
On the NASA website you can watch 2016 HO3 running around in orbit. As you can see (if you click the button in the upper right corner) its trajectory differs little from the trajectory of the 2018 RC
However, NASA somehow made another animation of asteroid 2016 HO3. There the movement is absolutely the same, but only the asteroid’s trajectory is shown as a continuous line:
As this animation clearly demonstrates, asteroid 2016 HO3 is something like a quasi-moon for the Earth, that is, like a satellite. This was not always the case and, according to NASA calculations, the Earth pulled 2016 HO3 into this cycle when it flew past at a distance of 100 distances from the Moon. Since then, it will continue to fly, approaching the Earth as close as possible to 38 lunar distances, and moving away from the Earth no more than 100 distances to the Moon.
What was the distance to asteroid 2018 RC at the time of September 9, 2018? And there was only half the lunar distance! In other words, if even at 100 distances to the Moon (40,000,000 km) the Earth pulled an asteroid into its orbit, then what are the chances of an asteroid at a distance 200 times less passing by calmly? None.
At the moment of its closest approach to the Earth on September 9, the speed of 2018 RC relative to the Earth was zero by cosmic standards - both bodies were flying on almost parallel courses with almost identical speeds of about 30 kilometers per second. Therefore, there is now no doubt that the orbit of 2018 RC has changed and become similar to that of 2016 HO3. That is, it will still circle around the Sun, simultaneously making loops around the Earth.
However, since 2018 RC at the time our planet was captured by gravity was 200 times closer to Earth than 2016 HO3, the asteroid will no longer circle forever, but sooner or later it will fall, this is inevitable. Perhaps this decline will last for several years, perhaps for several months or even weeks. The truth about the new trajectory of the 2018 RC is known only to NASA, but this truth will be revealed to the public only at the very last moment. Or, most likely, never at all.
The moon is a familiar part of the night landscape. She lights the way for couples in love, controls the ebb and flow of the tides, and causes werewolves to appear in horror films. But what if our planet had two satellites? Scientists say: nothing good.
Take two
Let's start with the fact that our Moon was formed 4.5 billion years ago, when it flew into the Earth huge asteroid the size of Mars. The debris from the impact flew into orbit and after some time turned into the Moon we are familiar with. And people were very lucky that they were not yet on the planet at that time.
The second moon would also bring a lot of trouble. Firstly, for it to appear, you also need a good lump from space. But even if you skip the period of formation of the second satellite and move on to the moment when two moons appear in the Earth’s sky at once, there is little positive.
The new moon's gravitational pull would create tides eight times higher than our current ones, with huge tidal waves larger than anything we've ever seen. This will lead to earthquakes and more volcanic activity, which will continue for many years and will ultimately lead to the mass extinction of marine life, which will affect the overall environmental situation. In addition, coastal cities: New York, San Francisco, Sydney, St. Petersburg will cease to exist due to destructive waves.
Lots of water and light
When the situation more or less improves, life on Earth will be completely different. At night it will be much brighter than during the day, thanks to the reflected light of two satellites at once. And the darkness of the night “even if you poke your eyes out” will be much less common.
True, some researchers are confident that the Earth already has two or even more satellites. The fact is that the planet “picks up” small asteroids that fly by, and they begin to rotate in Earth’s orbit for several weeks or months before they set off on space travel again.
Of course, such babies are unlikely to seriously influence what is happening on Earth. But such “colleagues” of the Moon are better than a full-fledged brother who can turn our lives around.
We all know and love the Moon. We are so sure that we only have one moon that we haven’t even given it a special name. Everyone has moons, we have the moon. This is the most bright object the night sky, and amateur astronomers take great pleasure in mapping its craters and seas. To date, this is the second celestial body in the Universe (as far as we know) with human footprints.
What you may not know is that the Moon is not Earth's only natural satellite. More recently, in 1997, we discovered another body, 3753 Cruithne, a so-called quasi-orbital satellite of the Earth. This means that Cruithney simply does not loop around the Earth in an ellipse, like the Moon or the artificial satellites we have launched into orbit. Cruithney orbits the inner solar system in a horseshoe-shaped orbit (above image).
To understand why this orbit is called a horseshoe, let's imagine that we are looking at the solar system and rotating at the same speed as the Earth revolves around the sun. From our point of view, the Earth will be stationary. A body in a simple horseshoe orbit moves toward Earth and then turns around and moves away. Then he approaches the Earth from the other side and leaves again.
Horseshoe orbits are quite common for moons in the Solar System. Saturn has several such moons, for example.
What is unique about Cruithney is that it swings along its horseshoe. If you look at Cruithney's motion in the solar system, it makes a rough circle around the Earth's orbit, swinging so far that it looks into the vicinity of Venus and Mars. Cruithney orbits the Sun once a year, but it takes about 800 years to complete this rough circle around the Earth's orbit.
So, “Cruithney” is our second moon. What does she look like? We don't really know. It is only five kilometers across, which is not much different from the size of comet 67P/Churyumov-Gerasimenko, which is currently being tracked by the Rosetta spacecraft on its way to the Sun.
Gravity on the surface of 67P is very weak - a brisk gait will most likely send you tumbling into space. This is why it was so important for the Philae lander to use its harpoons to cling to the surface, and why it bounced around when landing.
Considering that Cruithney is just a few fuzzy pixels in an image to us, it's safe to say that it is among the list of medium-sized celestial bodies in our system and that any robotic or human explorer would face the same difficulties as Rosetta " and "Philae" on 67P.
If Cruithney hits Earth, the impact will be terrible and result in a catastrophic level event similar to what happened at the end of the Cretaceous period. Fortunately, this certainly won't happen any time soon - astrophysicists have shown that although Cruithney may pass very close to us, it is unlikely to hit Earth. And this will happen in 2750 years.
In 8,000 years, Cruithney will have a fairly close encounter with Venus. There is a good chance that this will put an end to our free moon, throwing it out of our earthly family.
"Cruithney" is not everything
The story doesn't end there. Like a good home, the Earth plays host to many wayward lumps that seek a gravity well to get closer. Astronomers have discovered a number of other quasi-orbital satellites that are friendly to Earth and will stay with us for a while before moving on to pastures new.
What can we learn about the solar system from Cruithney? Quite a bit of. Like many other asteroids and comets, it contains physical evidence of how the planets came together. Its crazy orbit is perfect for learning how solar system develops under the influence of gravity.
Venus is a possible parent of the Moon
As we noted, until the end of the 20th century we did not even suspect that celestial bodies can go into such strange orbits and stay there for a long time. They also indicate that such interactions could occur when solar system was formed. And since we think that the planets terrestrial group formed in the process of collisions with bodies such as “Cruithney” and more, this is a new variable.
Cruithney could one day be a landing site for humans, and it could even be a mining site for the rare earth metals that our new technologies desperately need. And most importantly, “Cruithney” tells us that the solar system is not eternal - and, it turns out, neither are we.