Astronomers discover five rare galaxies that ‘interact with each other’

Astronomers have discovered an extremely rare group of five ‘dwarf galaxies’ ‘interacting’ about 117 million light-years from Earth

Dwarf galaxies contain a few billion stars, while standard galaxies have hundreds of billions, making them low in mass and brightness.

The newly found galaxies are blue, gas-rich and actively forming new stars.

Designated D1 through D5, D3 and D4 show signs of mutual tidal interactions, meaning their respective gravitational forces are pulling on each other and distorting the shapes of the galaxies.

D3 and D4 have developed “tidal tails,” or thin, elongated regions of stars and interstellar gas that extend far away from the point where the galaxies collide.

It is very unusual for dwarf galaxies to appear in groups, as research shows that less than five percent of dwarf galaxies are neighbors with each other.

So there is less than 0.004 percent chance that a dwarf galaxy is so close to four other galaxies.

Despite these incredibly low probabilities, “we have identified a distinct group of dwarf galaxies, all five of which are aligned on a straight line in the celestial plane and three of which share a common direction of rotation,” the researchers wrote in their report.

The discovery of this extraordinarily unique group forces scientists to question the prevailing model of our universe, but should also help scientists better understand how dwarf galaxies form and evolve.

A team of researchers led by Yonsei University in Seoul, South Korea, discovered the group of dwarf galaxies by analyzing data from several astronomical surveys that continually scour space for new discoveries.

These studies use telescopes to observe millions of celestial bodies in deep space, creating vast, highly detailed maps of the universe.

The researchers’ analysis revealed the presence of a group of dwarf galaxies isolated in deep space.

They estimated the group’s total dynamic mass — or the mass of an object inferred from its motion relative to other objects — to be about 60.2 billion times the mass of our Sun, the study found.

Their individual mass varies greatly. The largest member of the group, galaxy D2, has a stellar mass of about 275 million solar masses.

The least massive, D4, has a stellar mass of only 14.7 million solar masses.

For comparison, our galaxy – the Milky Way – has a stellar mass of about 1.5 trillion solar masses, according to NASA.

The researchers published their findings in The astrophysical diary letters on November 19.

They were labeled D1 to D5, and two of them – D3 and D4 – show signs of mutual tidal interactions, meaning their respective gravitational forces are pulling on each other and distorting the shapes of the galaxies.

Dwarf galaxies contain only a few billion stars, while standard galaxies have hundreds of billions. This is the irregular dwarf galaxy NGC 6822, which is not part of the newly found group

Finding five dwarf galaxies grouped in a nearly straight line, with most of them orbiting in the same direction, is so unusual that it calls into question the prevailing model’s predictions about the formation of the universe.

That model, called Lambda Cold Dark Matter (LCDM), suggests that dark matter creates disorderly groups of galaxies.

By that logic, galaxies are not expected to have a preferred direction. However, the five dwarf galaxies align in a configuration that is “not often seen in CDM simulations,” lead author Sanjaya Paudel of Yonsei University in South Korea told me. Space.com.

Furthermore, the fact that three of the five galaxies have the same rotation direction (as shown by DESI observations) suggests that they formed from the same gas cloud. This further contradicts the LCDM model.

“Why do they have the same rotation?” said Paedel. ‘They have to have a connection with each other. That would be a very strong question that cannot be explained by the ΛCDM model.”

Currently, this discovery raises more questions than answers. But future studies could quickly confirm whether the unlikely configuration of the galaxies is a chance projection or a real physical arrangement, the researchers said in their report.

Furthermore, studying these five dwarf galaxies could help scientists better understand how such objects form and evolve.

Astronomers believe that dwarf galaxies are formed by gravitational forces in the early stages of the formation of larger galaxies, or as a result of collisions between galaxies that eject streams of material into space.

According to the European Space Agency, dwarf galaxies are considered important to scientists’ understanding of the overall evolution of galaxies.

Those that have no defined shape – known as ‘irregular’ dwarf galaxies – are considered similar to the earliest galaxies that populated the universe. So studying it offers a glimpse into ancient cosmological history.

More than twenty known dwarf galaxies orbit the Milky Way. But they are separated in location and gravity and not grouped together.