5 ways to create a galaxy without dark matter

The full field of view of the array of telescopes " Dragonfly ", about 11 square meters. degrees centered on NGC 1052 . An increase indicates that it is next to NGC 1052; this, including the galaxy NGC1052 – DF2, taken out in the sidebar

In April 2018, astronomers announced the discovery of NGC 1052-DF2: a galaxy that does not contain dark matter.


A large, blurred galaxy is so sparse that astronomers call it “transparent,” because through it you can clearly see more distant galaxies. This ghostly object, cataloged as NGC 1052-DF2, does not have a noticeable central region or at least spiral arms and a disk — typical signs of a spiral galaxy. But it does not look like an elliptical galaxy. Even its globular star clusters are those strange: they are twice the size of the usual star clusters observed in other galaxies. But all these oddities fade in comparison with its strangest aspect: NGC 1052-DF2 has practically no, or even no, dark matter at all.

Although most dark matter galaxies are much larger than normal, this galaxy, located next to a giant elliptical galaxy, is practically absent.


The giant elliptical galaxy NGC 1052 (left) dominates its cluster, although there are other large galaxies in it. Nearby is a small, barely visible scattered galaxy, known as NGC 1052-DF2 (or simply DF2, for short), which, apparently, consists entirely of normal matter.

This is the first galaxy of this kind, but it does not disprove the theory [by reference - an article with the heading "Ghost galaxy without dark matter refutes the theory" / approx. trans.]. And here are five ways to create " DF2 ".


One of the fastest known galaxies of the universe, rushing through its cluster (losing gas on the way) at a speed of several percent of the speed of light, or thousands of km / h. In its wake, the trace of the stars remains, but dark matter still clings to it.

1) Gas ripped off from the galaxies inside the cluster. When galaxies quickly fly inside a cluster, their gas can break off from them, and generate new isolated stars without dark matter.


NGC 3561A and NGC 3561B collided and produced huge stellar traces, and even threw away some of the matter that condenses and creates “tiny” galaxies. Hot young stars glow blue where the formation of rejuvenated stars. This discarded material, which was part of a massive cluster of galaxies, can lead to the appearance of a galaxy very similar to DF2.

2) Matter discarded during galactic fusions. When two galaxies collide, they usually merge completely, but sometimes a piece of material is thrown away. A sufficient amount of it could generate only a baryon galaxy.


Although distant galaxies in which there are quasarsand active nuclei, often seen in visible or infrared light, relativistic jets and their surrounding radiation are best seen in the X-ray and radio frequency range, as shown here, using the example of Hercules A. galaxy. A massive outflow of matter could throw out a sufficient amount of material, which could lead to the appearance of a galaxy without dark matter or a set of several stars.

3) The outflow of matter of quasars. The outflow of matter caused by a supermassive black hole located in the center of a galaxy can shrink again and form a separate galaxy. Usually, dwarf galaxies appear this way, but DF2 is most likely larger.


Hanni Object, discovered in 2007 and named “Voorwerp”, was one of a couple of dozen strange objects. In 2011, it was identified as a cluster of green, luminous gas (due to ionized oxygen), stretching tens of thousands of light years, and located next to the galaxies. After a certain evolution, a similar object could create such a galaxy as DF2.

4) The evolving "worverpy." Galaxies sometimes have a green luminous companion - this is ionized matter torn from them.


Astronomers have discovered that the Hanni object is the only visible part of a gas tape stretching around the galaxy for 300,000 light years. The green object is visible because it is illuminated by the beam of the “spotlight” located in the galactic core. And this beam emits a quasar - a bright energetic object, fueled by a black hole. A meeting with another galaxy could turn into a “dinner” for a black hole, which pulled the gas strip out of IC 2497.

DF2 can be an evolved analogue of the Hanni object aged 10,000,000,000 years.


In theory, most of the dark matter in the galaxy exists in a huge halo encompassing us, or, alternatively, the laws of gravity change at large distances. A galaxy without dark matter may have properties that are different from the properties of galaxies with dark matter, but if dark matter does not exist at all, why would two different galaxies submit to different laws?

5) Dark matter does not exist. And while some galaxies experience normal gravity due to normal matter, not obeying the modified Newtonian dynamics (MOND) . Continuation of the rotation curve of M33, Triangle galaxy


. The rotation curves of spiral galaxies introduced the concept of dark matter into modern astrophysics. The movement of NGC 1052-DF2 very closely coincides with the dotted curve, which indicates the absence of dark matter.

If all galaxies obey the rules, only their composition can differ. The observed curves (black dots) together with the total amount of normal matter (blue curves) and various components, stars and gas, contribute to the rotation curves of galaxies. These rotation curves can explain both modified gravity and dark matter, but now a galaxy without dark matter, obeying the rules of gravity without modifications, defies the theory of MOND. From the absence of dark matter in this galaxy follows the abundance of dark matter in the universe.