Movement of the solar system in the Milky Way galaxy. Where are we going
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This article discusses the speed of the Sun and the Galaxy relative to different frames of reference:
The speed of the Sun in the Galaxy relative to the nearest stars, visible stars and the center of the Milky Way;
Velocity of the Galaxy relative to the local group of galaxies, distant star clusters and cosmic background radiation.
Brief description of the Milky Way Galaxy.
Description of the Galaxy.
Before proceeding to the study of the speed of the Sun and the Galaxy in the Universe, let's get to know our Galaxy better.
We live, as it were, in a gigantic "star city". Or rather, our Sun “lives” in it. The population of this "city" is a variety of stars, and more than two hundred billion of them "live" in it. A myriad of suns are born in it, going through their youth, middle age and old age - they go through a long and difficult life path lasting billions of years.
The dimensions of this "star city" - the Galaxy are enormous. The distances between neighboring stars are, on average, thousands of billions of kilometers (6*1013 km). And there are more than 200 billion such neighbors.
If we raced from one end of the Galaxy to the other at the speed of light (300,000 km/sec), it would take about 100,000 years.
Our entire star system slowly rotates like a giant wheel made up of billions of suns.
Orbit of the Sun
In the center of the Galaxy, apparently, there is a supermassive black hole (Sagittarius A *) (about 4.3 million solar masses) around which, presumably, a black hole of average mass from 1000 to 10,000 solar masses rotates and has an orbital period of about 100 years and several thousand relatively small ones. Their combined gravitational action on neighboring stars causes the latter to move along unusual trajectories. There is an assumption that most galaxies have supermassive black holes in their core.
The central regions of the Galaxy are characterized by a strong concentration of stars: each cubic parsec near the center contains many thousands of them. Distances between stars are tens and hundreds of times less than in the vicinity of the Sun.
The core of the Galaxy with great force attracts all other stars. But a huge number of stars are settled throughout the "star city". And they also attract each other in different directions, and this has a complex effect on the movement of each star. Therefore, the Sun and billions of other stars mostly move in circular paths or ellipses around the center of the Galaxy. But that's just "basically" - if we look closely, we'd see them moving in more complex curved, meandering paths among the surrounding stars.
Feature of the Milky Way Galaxy:
Location of the Sun in the Galaxy.
Where in the Galaxy is the Sun and does it move (and with it the Earth, and you and me)? Are we in the "city center" or at least somewhere close to it? Studies have shown that the Sun and the solar system are located at a great distance from the center of the Galaxy, closer to the "urban outskirts" (26,000 ± 1,400 light years).
The Sun is located in the plane of our Galaxy and is removed from its center by 8 kpc and from the plane of the Galaxy by about 25 pc (1 pc (parsec) = 3.2616 light years). In the region of the Galaxy where the Sun is located, the stellar density is 0.12 stars per pc3.
model of our galaxy
The speed of the Sun in the Galaxy.
The speed of the Sun in the Galaxy is usually considered relative to different frames of reference:
relative to nearby stars.
Relative to all bright stars visible to the naked eye.
Regarding interstellar gas.
Relative to the center of the Galaxy.
1. The speed of the Sun in the Galaxy relative to the nearest stars.
Just as the speed of a flying aircraft is considered in relation to the Earth, not taking into account the flight of the Earth itself, so the speed of the Sun can be determined relative to the stars closest to it. Such as the stars of the Sirius system, Alpha Centauri, etc.
This velocity of the Sun in the Galaxy is relatively small: only 20 km/sec or 4 AU. (1 astronomical unit is equal to the average distance from the Earth to the Sun - 149.6 million km.)
The Sun, relative to the nearest stars, moves towards a point (apex) lying on the border of the constellations Hercules and Lyra, approximately at an angle of 25 ° to the plane of the Galaxy. Equatorial coordinates of the apex = 270°, = 30°.
2. The speed of the Sun in the Galaxy relative to the visible stars.
If we consider the movement of the Sun in the Milky Way Galaxy relative to all the stars visible without a telescope, then its speed is even less.
The speed of the Sun in the Galaxy relative to the visible stars is 15 km/sec or 3 AU.
The apex of the motion of the Sun in this case also lies in the constellation Hercules and has the following equatorial coordinates: = 265°, = 21°.
The speed of the Sun relative to nearby stars and interstellar gas
3. The speed of the Sun in the Galaxy relative to the interstellar gas.
The next object of the Galaxy, with respect to which we will consider the speed of the Sun, is interstellar gas.
The expanses of the universe are far from being as desolate as it was thought for a long time. Although in small quantities, interstellar gas is present everywhere, filling all corners of the universe. The interstellar gas, with the apparent emptiness of the unfilled space of the Universe, accounts for almost 99% of the total mass of all space objects. Dense and cold forms of interstellar gas containing hydrogen, helium and minimal amounts of heavy elements (iron, aluminum, nickel, titanium, calcium) are in a molecular state, combining into vast cloud fields. Usually, in the composition of the interstellar gas, the elements are distributed as follows: hydrogen - 89%, helium - 9%, carbon, oxygen, nitrogen - about 0.2-0.3%.
A tadpole-like cloud of interstellar gas and dust IRAS 20324+4057 that hides a growing star
Clouds of interstellar gas can not only rotate in an orderly manner around galactic centers, but also have unstable acceleration. Over the course of several tens of millions of years, they catch up with each other and collide, forming complexes of dust and gas.
In our Galaxy, the main volume of interstellar gas is concentrated in spiral arms, one of the corridors of which is located near the solar system.
The speed of the Sun in the Galaxy relative to the interstellar gas: 22-25 km/sec.
Interstellar gas in the immediate vicinity of the Sun has a significant intrinsic velocity (20-25 km/s) relative to the nearest stars. Under its influence, the apex of the Sun's motion shifts towards the constellation Ophiuchus (= 258°, = -17°). The difference in direction of movement is about 45°.
4. The speed of the Sun in the Galaxy relative to the center of the Galaxy.
In the three points discussed above, we are talking about the so-called peculiar, relative speed of the Sun. In other words, peculiar speed is the speed relative to the cosmic frame of reference.
But the Sun, the stars closest to it, and the local interstellar cloud are all involved in a larger movement - movement around the center of the Galaxy.
And here we are talking about completely different speeds.
The speed of the Sun around the center of the Galaxy is huge by earthly standards - 200-220 km / s (about 850,000 km / h) or more than 40 AU. / year.
It is impossible to determine the exact speed of the Sun around the center of the Galaxy, because the center of the Galaxy is hidden from us behind dense clouds of interstellar dust. However, more and more new discoveries in this area are decreasing the estimated speed of our sun. More recently, they talked about 230-240 km / s.
The solar system in the galaxy is moving towards the constellation Cygnus.
The motion of the Sun in the Galaxy occurs perpendicular to the direction to the center of the Galaxy. Hence the galactic coordinates of the apex: l = 90°, b = 0° or in more familiar equatorial coordinates - = 318°, = 48°. Since this is a reversal motion, the apex shifts and completes a full circle in a "galactic year", approximately 250 million years; its angular velocity is ~5" / 1000 years, i.e. the coordinates of the apex shift by one and a half degrees per million years.
Our Earth is about 30 such "galactic years" old.
The speed of the Sun in the Galaxy relative to the center of the Galaxy
By the way, an interesting fact about the speed of the Sun in the Galaxy:
The speed of rotation of the Sun around the center of the Galaxy almost coincides with the speed of the compression wave that forms the spiral arm. This situation is atypical for the Galaxy as a whole: the spiral arms rotate at a constant angular velocity, like spokes in wheels, and the movement of stars occurs with a different pattern, so almost the entire stellar population of the disk either gets inside the spiral arms or falls out of them. The only place where the speeds of stars and spiral arms coincide is the so-called corotation circle, and it is on it that the Sun is located.
For the Earth, this circumstance is extremely important, since violent processes occur in the spiral arms, which form powerful radiation that is destructive to all living things. And no atmosphere could protect him from it. But our planet exists in a relatively quiet place in the Galaxy and has not been affected by these cosmic cataclysms for hundreds of millions (or even billions) of years. Perhaps that is why life was able to originate and survive on Earth.
The speed of movement of the Galaxy in the Universe.
The speed of movement of the Galaxy in the Universe is usually considered relative to different frames of reference:
Relative to the Local Group of galaxies (speed of approach to the Andromeda galaxy).
Relative to distant galaxies and clusters of galaxies (the speed of movement of the Galaxy as part of the local group of galaxies to the constellation Virgo).
Regarding the relic radiation (the speed of movement of all galaxies in the part of the Universe closest to us to the Great Attractor - a cluster of huge supergalaxies).
Let's take a closer look at each of the points.
1. Velocity of movement of the Milky Way Galaxy towards Andromeda.
Our Milky Way Galaxy also does not stand still, but is gravitationally attracted and approaches the Andromeda galaxy at a speed of 100-150 km/s. The main component of the speed of approach of galaxies belongs to the Milky Way.
The lateral component of the motion is not precisely known, and it is premature to worry about a collision. An additional contribution to this motion is made by the massive galaxy M33, located approximately in the same direction as the Andromeda galaxy. In general, the speed of our Galaxy relative to the barycenter of the Local Group of galaxies is about 100 km / s approximately in the Andromeda/Lizard direction (l = 100, b = -4, = 333, = 52), however, these data are still very approximate. This is a very modest relative speed: the Galaxy is displaced by its own diameter in two or three hundred million years, or, very approximately, in a galactic year.
2. Velocity of movement of the Milky Way Galaxy towards the Virgo cluster.
In turn, the group of galaxies, which includes our Milky Way, as a whole, is moving towards the large cluster of Virgo at a speed of 400 km/s. This movement is also due to gravitational forces and is carried out relative to distant clusters of galaxies.
Velocity of the Milky Way Galaxy towards the Virgo Cluster
3. Speed of movement of the Galaxy in the Universe. To the Great Attractor!
Relic radiation.
According to the Big Bang theory, the early Universe was a hot plasma consisting of electrons, baryons, and constantly emitted, absorbed, and re-emitted photons.
As the Universe expanded, the plasma cooled down and at a certain stage, slowed down electrons got the opportunity to combine with slowed down protons (hydrogen nuclei) and alpha particles (helium nuclei), forming atoms (this process is called recombination).
This happened at a plasma temperature of about 3,000 K and an approximate age of the universe of 400,000 years. There is more free space between particles, fewer charged particles, photons no longer scatter so often and can now move freely in space, practically without interacting with matter.
Those photons that were emitted at that time by the plasma towards the future location of the Earth still reach our planet through the space of the universe that continues to expand. These photons make up the relic radiation, which is thermal radiation that evenly fills the Universe.
The existence of relic radiation was theoretically predicted by G. Gamow in the framework of the Big Bang theory. Its existence was experimentally confirmed in 1965.
Velocity of movement of the Galaxy relative to the cosmic background radiation.
Later, the study of the speed of movement of galaxies relative to the cosmic background radiation began. This movement is determined by measuring the non-uniformity of the temperature of the relict radiation in different directions.
The radiation temperature has a maximum in the direction of motion and a minimum in the opposite direction. The degree of deviation of the temperature distribution from isotropic (2.7 K) depends on the magnitude of the velocity. It follows from the analysis of the observational data that the Sun moves relative to the cosmic microwave background at a speed of 400 km/s in the direction =11.6, =-12.
Such measurements also showed another important thing: all galaxies in the part of the Universe closest to us, including not only ours local group, but also the Virgo cluster and other clusters, move relative to the background cosmic microwave background at an unexpectedly high speed.
For the Local Group of galaxies, it is 600-650 km / s with an apex in the constellation Hydra (=166, =-27). It looks like that somewhere in the depths of the Universe there is a huge cluster of many superclusters that attract the matter of our part of the Universe. This cluster was named Great Attractor- from the English word "attract" - to attract.
Since the galaxies that make up the Great Attractor are hidden by interstellar dust that is part of the Milky Way, mapping of the Attractor has only been possible in recent years with the help of radio telescopes.
The Great Attractor is located at the intersection of several superclusters of galaxies. The average density of matter in this region is not much greater than the average density of the Universe. But due to its gigantic size, its mass turns out to be so great and the force of attraction is so huge that not only our star system, but also other galaxies and their clusters nearby move in the direction of the Great Attractor, forming a huge stream of galaxies.
The speed of movement of the Galaxy in the Universe. To the Great Attractor!
So, let's sum up.
The speed of the Sun in the Galaxy and the Galaxy in the Universe. Pivot table.
Hierarchy of movements in which our planet takes part:
The rotation of the Earth around the Sun;
Rotation together with the Sun around the center of our Galaxy;
Movement relative to the center of the Local Group of galaxies together with the entire Galaxy under the influence of the gravitational attraction of the constellation Andromeda (galaxy M31);
Movement towards a cluster of galaxies in the constellation Virgo;
Movement to the Great Attractor.
The speed of the Sun in the Galaxy and the speed of the Milky Way Galaxy in the Universe. Pivot table.
It is difficult to imagine, and even more difficult to calculate, how far we move every second. These distances are huge, and the errors in such calculations are still quite large. Here is what science has to date.
Surely, many of you have seen a gif or watched a video showing the movement of the solar system.
Video clip, released in 2012, went viral and made a lot of noise. I came across him shortly after his appearance, when I knew much less about space than I do now. And most of all I was confused by the perpendicularity of the plane of the orbits of the planets to the direction of motion. It's not that it's impossible, but the Solar System can move at any angle to the plane of the Galaxy. You ask, why remember long-forgotten stories? The fact is that right now, with the desire and the presence of good weather, everyone can see in the sky the real angle between the planes of the ecliptic and the Galaxy.
We check scientists
Astronomy says that the angle between the planes of the ecliptic and the galaxy is 63°.
But the figure itself is boring, and even now, when adherents of the flat Earth are on the sidelines of science, I want to have a simple and clear illustration. Let's think about how we can see the planes of the Galaxy and the ecliptic in the sky, preferably with the naked eye and without moving far from the city? The plane of the Galaxy is the Milky Way, but now, with an abundance of light pollution, it is not so easy to see it. Is there any line approximately close to the plane of the Galaxy? Yes, it is the constellation Cygnus. It is clearly visible even in the city, and it is easy to find it, relying on the bright stars: Deneb (alpha Cygnus), Vega (alpha Lyra) and Altair (alpha Eagle). The "trunk" of Cygnus approximately coincides with the galactic plane.
Okay, we have one plane. But how to get a visual line of the ecliptic? Let's think, what is the ecliptic in general? According to the modern strict definition, the ecliptic is a section of the celestial sphere by the plane of the orbit of the barycenter (center of mass) of the Earth-Moon. On the average, the Sun moves along the ecliptic, but we do not have two Suns, according to which it is convenient to draw a line, and the Cygnus constellation will not be visible in sunlight. But if we remember that the planets of the solar system also move approximately in the same plane, then it turns out that the parade of planets will just approximately show us the plane of the ecliptic. And now in the morning sky you can just see Mars, Jupiter and Saturn.
As a result, in the coming weeks, in the morning before sunrise, it will be possible to very clearly see the following picture:
Which, surprisingly, is in perfect agreement with astronomy textbooks.
And it's better to draw a gif like this:
Source: astronomer Rhys Taylor website rhysy.net
The question can cause the relative position of the planes. Are we flying<-/ или же <-\ (если смотреть с внешней стороны Галактики, северный полюс вверху)? Астрономия говорит, что Солнечная система движется относительно ближайших звезд в направлении созвездия Геркулеса, в точку, расположенную недалеко от Веги и Альбирео (бета Лебедя), то есть правильное положение <-/.
But this fact, alas, cannot be verified "on the fingers", because, even if they did it two hundred and thirty-five years ago, they used the results of many years of astronomical observations and mathematics.
Receding stars
How can you generally determine where the solar system is moving relative to nearby stars? If we can record the movement of a star across the celestial sphere for decades, then the direction of movement of several stars will tell us where we are moving relative to them. Let's call the point to which we are moving, the apex. Stars that are not far from it, as well as from the opposite point (anti-apex), will move weakly, because they are flying towards us or away from us. And the farther the star is from the apex and anti-apex, the greater will be its own motion. Imagine that you are driving down the road. Traffic lights at intersections in front and behind will not shift much to the sides. But the lampposts along the road will flicker (have a large own movement) outside the window.
The gif shows the movement of Barnard's star, which has the largest proper motion. Already in the 18th century, astronomers had records of the position of stars over an interval of 40-50 years, which made it possible to determine the direction of motion of slower stars. Then the English astronomer William Herschel took the star catalogs and, without approaching the telescope, began to calculate. Already the first calculations according to Mayer's catalog showed that the stars do not move randomly, and the apex can be determined.
Source: Hoskin, M. Herschel's Determination of the Solar Apex, Journal for the History of Astronomy, Vol. 11, P. 153, 1980
And with the data of the Lalande catalog, the area was significantly reduced.
From there
Then normal scientific work went on - data clarification, calculations, disputes, but Herschel used the correct principle and was only ten degrees wrong. Information is still being collected, for example, only thirty years ago, the speed of movement was reduced from 20 to 13 km / s. Important: this speed should not be confused with the speed of the solar system and other nearby stars relative to the center of the Galaxy, which is approximately 220 km/s.
Even further
Well, since we mentioned the speed of movement relative to the center of the Galaxy, it is necessary to understand here as well. The galactic north pole is chosen in the same way as the earth's - arbitrarily by agreement. It is located near the star Arcturus (alpha Bootes), approximately up in the direction of the wing of the constellation Cygnus. But in general, the projection of the constellations on the map of the Galaxy looks like this:
Those. The solar system moves relative to the center of the Galaxy in the direction of the constellation Cygnus, and relative to the local stars in the direction of the constellation Hercules, at an angle of 63 ° to the galactic plane,<-/, если смотреть с внешней стороны Галактики, северный полюс сверху.
space tail
But the comparison of the solar system with a comet in the video is absolutely correct. NASA's IBEX was specifically designed to determine the interaction between the boundary of the solar system and interstellar space. And according to him, there is a tail.
NASA illustration
For other stars, we can see the astrospheres (stellar wind bubbles) directly.
Photo by NASA
Positive in the end
Concluding the conversation, it is worth noting a very positive story. DJSadhu, who created the original video in 2012, originally promoted something unscientific. But, thanks to the viral distribution of the clip, he talked to real astronomers (astrophysicist Rhys Tailor speaks very positively about the dialogue) and, three years later, made a new video that is much more relevant to reality without anti-scientific constructions.Any person, even lying on the couch or sitting near the computer, is in constant motion. This continuous movement in outer space has a variety of directions and tremendous speeds. First of all, the Earth moves around its axis. In addition, the planet revolves around the sun. But that's not all. Much more impressive distances we overcome together with the solar system.
Location of the solar system
The sun is one of the stars in the plane of the Milky Way, or simply the Galaxy. It is 8 kpc away from the center, and the distance from the plane of the Galaxy is 25 pc. The stellar density in our region of the Galaxy is approximately 0.12 stars per 1 pc3. The position of the solar system is not constant: it is in constant motion relative to nearby stars, interstellar gas, and finally around the center of the Milky Way. The movement of the solar system in the galaxy was first noticed by William Herschel.
Movement relative to nearby stars
The speed of movement of the Sun to the border of the constellations Hercules and Lyra is 4 a.s. per year, or 20 km/s. The velocity vector is directed towards the so-called apex - a point to which the movement of other nearby stars is also directed. Directions of velocities of stars, incl. The suns intersect at the point opposite to the apex, called the anti-apex.
Moving relative to visible stars
Separately, the movement of the Sun in relation to bright stars that can be seen without a telescope is measured. This is an indicator of the standard movement of the Sun. The speed of such movement is 3 AU. per year or 15 km/s.
Movement relative to interstellar space
In relation to interstellar space, the solar system is already moving faster, the speed is 22-25 km / s. At the same time, under the influence of the "interstellar wind", which "blowing" from the southern region of the Galaxy, the apex shifts to the constellation Ophiuchus. The shift is estimated at about 50.
Moving around the center of the Milky Way
The solar system is in motion relative to the center of our galaxy. It moves towards the constellation Cygnus. The speed is about 40 AU. per year, or 200 km/s. It takes 220 million years for a complete revolution. It is impossible to determine the exact speed, because the apex (the center of the Galaxy) is hidden from us behind dense clouds of interstellar dust. The apex shifts 1.5° every million years, and completes a full circle in 250 million years, or 1 "galactic year.
Journey to the edge of the Milky Way
Movement of the Galaxy in outer space
Our Galaxy also does not stand still, but approaches the Andromeda galaxy at a speed of 100-150 km/s. A group of galaxies, which includes the Milky Way, is moving towards the large cluster of Virgo at a speed of 400 km/s. It is difficult to imagine, and even more difficult to calculate, how far we move every second. These distances are huge, and the errors in such calculations are still quite large.
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You are sitting, standing or lying down reading this article, and you do not feel that the Earth is rotating around its axis at a breakneck speed - about 1,700 km / h at the equator. However, the rotation speed doesn't seem all that fast when converted to km/s. It turns out 0.5 km / s - a barely noticeable flash on the radar, in comparison with other speeds around us.
Just like other planets in the solar system, the Earth revolves around the Sun. And in order to stay in its orbit, it moves at a speed of 30 km / s. Venus and Mercury, which are closer to the Sun, move faster, Mars, whose orbit passes the orbit of the Earth, moves much more slowly.
But even the Sun does not stand in one place. Our Milky Way galaxy is huge, massive and also mobile! All stars, planets, gas clouds, dust particles, black holes, dark matter - all this moves relative to a common center of mass.
According to scientists, the Sun is located at a distance of 25,000 light-years from the center of our galaxy and moves in an elliptical orbit, making a complete revolution every 220-250 million years. It turns out that the speed of the Sun is about 200-220 km / s, which is hundreds of times higher than the speed of the Earth around its axis and tens of times higher than the speed of its movement around the Sun. This is what the movement of our solar system looks like.
Is the galaxy stationary? Again no. Giant space objects have a large mass, and therefore, create strong gravitational fields. Give the Universe a little time (and we had it - about 13.8 billion years), and everything will begin to move in the direction of the greatest attraction. That is why the Universe is not homogeneous, but consists of galaxies and groups of galaxies.
What does this mean for us?
This means that the Milky Way is pulled towards itself by other galaxies and groups of galaxies located nearby. This means that massive objects dominate this process. And this means that not only our galaxy, but also all those around us are influenced by these "tractors". We are getting closer to understanding what happens to us in outer space, but we still lack facts, for example:
- what were the initial conditions under which the universe was born;
- how the various masses in the galaxy move and change over time;
- how the Milky Way and surrounding galaxies and clusters formed;
- and how it is now.
However, there is a trick that will help us figure it out.
The universe is filled with cosmic microwave background radiation with a temperature of 2.725 K, which has been preserved since the time of the Big Bang. In some places there are tiny deviations - about 100 μK, but the general temperature background is constant.
This is because the universe was formed in the Big Bang 13.8 billion years ago and is still expanding and cooling.
380,000 years after the Big Bang, the universe cooled to such a temperature that it became possible for the formation of hydrogen atoms. Prior to this, photons constantly interacted with the rest of the plasma particles: they collided with them and exchanged energy. As the universe cools, there are fewer charged particles, and more space between them. Photons were able to move freely in space. Relic radiation is photons that were emitted by the plasma towards the future location of the Earth, but avoided scattering, since recombination has already begun. They reach the Earth through the space of the Universe, which continues to expand.
You can "see" this radiation yourself. The interference that occurs on an empty TV channel if you use a simple bunny-ear antenna is 1% due to CMB.
And yet the temperature of the background background is not the same in all directions. According to the results of the Planck mission research, the temperature differs somewhat in the opposite hemispheres of the celestial sphere: it is slightly higher in the areas of the sky south of the ecliptic - about 2.728 K, and lower in the other half - about 2.722 K.
Microwave background map made with the Planck telescope. This difference is almost 100 times greater than the rest of the observed CMB temperature fluctuations, and this is misleading. Why it happens? The answer is obvious - this difference is not due to fluctuations in the background radiation, it appears because there is movement!
When you approach a light source or it approaches you, the spectral lines in the spectrum of the source shift towards short waves (violet shift), when you move away from it or it moves away from you, the spectral lines shift towards long waves (red shift).
The relic radiation cannot be more or less energetic, which means we are moving through space. The Doppler effect helps to determine that our solar system is moving relative to the CMB at a speed of 368 ± 2 km/s, and the local group of galaxies, including the Milky Way, the Andromeda Galaxy and the Triangulum Galaxy, is moving at a speed of 627 ± 22 km/s relative to the CMB. These are the so-called peculiar velocities of galaxies, which are several hundred km/s. In addition to them, there are also cosmological velocities due to the expansion of the Universe and calculated according to the Hubble law.
Thanks to the residual radiation from the Big Bang, we can observe that everything in the universe is constantly moving and changing. And our galaxy is only a part of this process.
Even sitting in a chair in front of a computer screen and clicking on links, we are physically participating in many movements. Where are we heading? Where is the "top" of the movement, its apex?
First, we participate in the rotation of the Earth around its axis. This diurnal movement pointing east on the horizon. The speed of movement depends on the latitude; it is equal to 465*cos(φ) m/sec. Thus, if you are at the north or south pole of the Earth, then you are not participating in this movement. And let's say, in Moscow, the daily linear speed is about 260 m / s. The angular velocity of the apex of the daily motion relative to the stars is easy to calculate: 360° / 24 hours = 15° / hour.
Secondly, the Earth, and we along with it, moves around the Sun. (We will neglect the small monthly wobble around the center of mass of the Earth-Moon system.) Average speed annual movement in orbit - 30 km / s. At perihelion in early January it is slightly higher, at aphelion in early July it is slightly lower, but since the Earth's orbit is almost an exact circle, the speed difference is only 1 km / s. The apex of the orbital movement naturally shifts and makes a full circle in a year. Its ecliptic latitude is 0 degrees, and its longitude is equal to the longitude of the Sun plus approximately 90 degrees - λ=λ ☉ +90°, β=0. In other words, the apex lies on the ecliptic, 90 degrees ahead of the Sun. Accordingly, the angular velocity of the apex is equal to the angular velocity of the Sun: 360° / year, slightly less than a degree per day.
We are already carrying out larger movements together with our Sun as part of the Solar System.
First, the Sun moves relative to nearby stars(so-called local rest standard). The speed of movement is approximately 20 km / sec (slightly more than 4 AU / year). Note that this is even less than the Earth's orbital speed. The movement is directed towards the constellation Hercules, and the equatorial coordinates of the apex are α = 270°, δ = 30°. However, if we measure the speed relative to all bright stars, visible to the naked eye, then we get the standard motion of the Sun, it is somewhat different, slower in speed 15 km / s ~ 3 AU. / year). This is also the constellation Hercules, although the apex is slightly offset (α = 265°, δ = 21°). But relative to the interstellar gas, the solar system moves slightly faster (22-25 km / sec), but the apex is significantly shifted and falls into the constellation Ophiuchus (α = 258°, δ = -17°). This apex shift of about 50° is associated with the so-called. "interstellar wind" "blowing from the south" of the Galaxy.
All three movements described are, so to speak, local movements, "walks in the yard." But the Sun, together with the nearest and generally visible stars (after all, we practically do not see very distant stars), together with clouds of interstellar gas, revolves around the center of the Galaxy - and these are completely different speeds!
The speed of the solar system around center of the galaxy is 200 km/sec (greater than 40 AU/year). However, the indicated value is inaccurate, it is difficult to determine the galactic speed of the Sun; we don't even see what we're measuring motion against: the center of the Galaxy is hidden by dense interstellar dust clouds. The value is constantly refined and tends to decrease; not so long ago it was taken as 230 km / s (it is often possible to meet exactly this value), and recent studies give results even less than 200 km / s. Galactic motion occurs perpendicular to the direction to the center of the Galaxy and therefore the apex has galactic coordinates l = 90°, b = 0° or in more familiar equatorial coordinates - α = 318°, δ = 48°; this point is in Cygnus. Since this is a reversal motion, the apex shifts and completes a full circle in a "galactic year", approximately 250 million years; its angular velocity is ~5" / 1000 years, one and a half degrees per million years.
Further movements include the movement of the entire Galaxy. It is also not easy to measure such a movement, the distances are too large, and the error in the numbers is still quite large.
Thus, our Galaxy and the Andromeda Galaxy, two massive objects of the Local Group of Galaxies, are gravitationally attracted and move towards each other at a speed of about 100-150 km/s, with the main component of the speed belonging to our galaxy. The lateral component of the motion is not precisely known, and it is premature to worry about a collision. An additional contribution to this motion is made by the massive galaxy M33, located approximately in the same direction as the Andromeda galaxy. In general, the speed of our Galaxy relative to the barycenter Local group of galaxies about 100 km / s approximately in the direction of Andromeda / Lizard (l = 100, b = -4, α = 333, δ = 52), however, these data are still very approximate. This is a very modest relative speed: the Galaxy shifts by its own diameter in two to three hundred million years, or, very roughly, in galactic year.
If we measure the speed of the Galaxy relative to distant clusters of galaxies, we will see a different picture: both our galaxy and the rest of the galaxies of the Local Group are moving together as a whole in the direction of the large Virgo cluster at about 400 km/sec. This movement is also due to gravitational forces.
background background radiation defines some selected reference system associated with all baryonic matter in the observable part of the Universe. In a sense, motion relative to this microwave background is motion relative to the Universe as a whole (this motion should not be confused with the recession of galaxies!). This movement can be determined by measuring dipole temperature anisotropy non-uniformity of relic radiation in different directions. Such measurements showed an unexpected and important thing: all galaxies in the part of the Universe closest to us, including not only our Local Group, but also the Virgo Cluster and other clusters, move relative to the background cosmic microwave background radiation at an unexpectedly high speed. For the Local Group of galaxies, it is 600-650 km / s with an apex in the constellation Hydra (α=166, δ=-27). It looks like that somewhere in the depths of the Universe there is still an undiscovered huge cluster of many superclusters that attracts the matter of our part of the Universe. This hypothetical cluster has been named Great Attractor.
How was the speed of the Local Group of Galaxies determined? Of course, in fact, astronomers measured the speed of the Sun relative to the microwave background background: it turned out to be ~390 km / s with an apex with coordinates l = 265°, b = 50° (α=168, δ=-7) on the border of the constellations Leo and Chalice. Then determine the speed of the Sun relative to the galaxies of the Local Group (300 km / s, the constellation Lizard). Calculating the speed of the Local Group was no longer difficult.
| Diurnal: observer relative to the center of the Earth | 0-465 m/s | East |
| Annual: Earth relative to the Sun | 30 km/sec | perpendicular to the direction of the sun |
| Local: Sun relative to nearby stars | 20 km/sec | Hercules |
| Standard: Sun relative to bright stars | 15 km/sec | Hercules |
| Sun relative to interstellar gas | 22-25 km/sec | Ophiuchus |
| Sun relative to the center of the Galaxy | ~ 200 km/sec | Swan |
| The Sun in relation to the Local Group of Galaxies | 300 km/sec | Lizard |
| Galaxy relative to the Local Group of Galaxies | ~1 00 km/s |