Do Smaller Galaxies Lose Their Dark Matter on Collisions? Here’s What Experts Say

While giant galaxies may take dark matter from smaller galaxies they almost collide with, astronomers believe galaxies may persist without a halo of dark matter.

It's a discovery that not only broadens scientists' knowledge of galaxy history and behavior but also retains the crucial role of dark matter in the universe and points to vital future investigations for the James Webb Space Telescope, which was recently launched.

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SYDNEY, AUSTRALIA - MARCH 31: The Milky Way and the Southern Cross become visible above the Sydney Opera House during Earth Hour March 31, in Sydney, Australia. The entire city of Sydney, including companies, government departments, individuals and families have been urged to switch off their lights for one hour. The event is the launch of a 12 month campaign organised by WWF (World Wide Fund for Nature) Australia to reduce Sydney's greenhouse gas emissions by 5%.

Small Galaxies Can Keep Stars Despite Giant Galaxies Stealing Dark Matter

How do these tiny galaxies keep their stars despite losing most of their dark matter and gas? Sky and Telescope, citing the researchers, said multiple near approaches by their host galaxies are to blame.

While the satellite galaxies lost "just" 45-97 percent of their stars and gas, tidal interactions robbed them of 97.9 to 99.99 percent of their dark matter.

Dark matter particles may be more vulnerable to lose due to their more eccentric orbits - they don't interact with each other through any means other than gravity, making it difficult for the orbits to circularize over time.

The satellite must travel directly through the host's star body for this specific tidal stripping to occur.

Researchers used high-powered computer simulations of galaxies to prove that, contrary to astronomers' expectations, galaxies may persist without a halo of dark matter surrounding them, according to Space.com.

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The issue is that such galaxies must survive near encounters with galaxies that are considerably more massive, passing through the bigger galaxy and losing their dark matter.

In 2018, a group of Yale astronomers found NGC 1052-DF2, a dwarf galaxy with little or no dark matter. Dark matter is a mysterious substance that accounts for 85 percent of the universe's mass.

Although scientists can't detect dark matter, they can sense its gravitational effects, and it's thought that the mysterious substance aids in the formation and maintenance of galaxies.

A second galaxy, AGC 114905, was recently discovered to contain very little or no dark matter, posing a severe dilemma for astronomers researching galaxies.

Implication Of Study

According to The Independent, this proof of concept has various consequences.

First, it explains the observed galaxies' mysterious lack of dark matter.

However, the discovery adds to the evidence for dark matter's existence in the cosmos. The researchers stated that the Dark Matter model was salvaged rather than destroyed.

The final implication of the new results is relevant in the realm of science and astrophysics and the world of scientists and astrophysicists themselves.

Researchers published their study, "Galaxies Lacking Dark Matter Produced by Close Encounters in a Cosmological Simulation," in Nature Astronomy.