Galaxy Centaurus A is located about 10 to 16 million light-years from the solar system and is in the constellation Centauri. It is very close, but nevertheless does not belong to the Local Group of Galaxies, and is also the closest active galaxy to us, which means that it is very bright and is a very powerful source of radio emission. In addition, it has an unusual form – a lens-shaped galaxy with a polar ring. And now the Centaurus A was also the first galaxy outside of the Local Group, in which scientists discovered dwarf galaxy satellites that rotate with it in the same plane.
The Milky Way and Andromeda also have dwarf galaxies that rotate with them in the same plane, but the cosmological models built on the standard Lambda-CDM model predict that more often compact galaxies revolve around larger ones chaotically, moving in all directions that in the turn makes the Milky Way and Andromeda the exception to this rule. However, a new observation of Centaur A disproves this conclusion.
“The Lambda-CDM model made astronomers believe that the galaxies we studied most in the universe, the Milky Way and Andromeda, stand out among all others,” explains researcher Helmut Jerzhen from the Australian State University School of Astronomy and Astrophysics.
“But it seems that our Milky Way and Andromeda are quite normal, and galaxies that rotate in the same plane with other galaxies are in fact very common in the universe.”
And yet the rotation of the satellite galaxies is somewhat different from the rotation of the planets around their stars. The latter, as a rule, turn around the equator of their luminaries. As for satellite satellites, such as those that revolve around Centaurus A, as well as around the Milky Way, and Andromeda, they circulate around larger galaxies perpendicular to their equatorial plane, that is, around the poles of supermassive black holes located in their centers.
Model rotation of dwarf galaxies around the galaxy Centaurus A
The researchers say that it is quite easy to discover the galactic planes for the Milky Way and Andromeda. While on Earth, you need to take pictures of the sky every few years and watch where the stars are at this moment. Andromeda is located about 2.5 million light-years from us, so the perpendicular plane of rotation of dwarf galaxies is also not difficult to find.
With the Centaurus A plane, everything turned out to be somewhat more complicated. However, the huge amount of archival data collected about this galaxy allowed the team of scientists to discover information about at least 16 dwarf galaxies revolving around it. And the Doppler effect made it possible to determine the direction in which these dwarf galaxies move.
“We found that half of them have a red shift, meaning that they are moving away from us, while the other half has a blue shift, which indicates that they are, on the contrary, moving in our direction,” explains the astronomer Marcel Pavlovski from the University of California at Irvine (USA).
Based on this, the scientists found out that 14 of the 16 satellite galaxies have the same plane of rotation. For example, in the same Milky Way of 11 satellite galaxies, only 8 revolve with it in one perpendicular plane. And among the 27 galaxies found around Andromeda, the perpendicular plane of rotation is 15.
Since the phenomenon discussed today is already observed for the third time, then, according to researchers, the randomness factor can be safely discarded. In addition, this also implies that this phenomenon should occur much more often than previously thought – according to standard models, this feature should be observed only in 0.5% of neighboring galaxies. But we see that this is not so.
“This means that we have missed something,” Pavlovski says.
“Either the simulation models have some kind of omissions, or our conventional model actually turned out to be wrong. The results of this study can be a starting point in the search for alternative models that explain our observation. ”
The head of the study, Oliver Müller from the University of Basel, Switzerland, adds that the results also support the idea that collisions between two large galaxies (which happens quite often) can generate dwarf galaxies from the matter discarded as a result of these collisions attracted by tidal forces.
