Dienstag, August 2, 2022
StartScience NewsA galactic smashup would possibly clarify galaxies with out darkish matter

A galactic smashup would possibly clarify galaxies with out darkish matter


Two mysterious galaxies, devoid of darkish matter, might have a smashing origin story.

About 8 billion years in the past, researchers suggest, two dwarf galaxies slammed into each other. That cosmic crash induced the fuel inside these two galaxies to separate up and kind a number of new dwarf galaxies, together with the 2 darkish matter–free ones.

A newfound row of dwarf galaxies, greater than 6 million light-years lengthy, might have shaped within the aftermath of the hypothesized crash, researchers report within the Might 19 Nature. If right, the discovering might assist resolve the thriller of how such uncommon darkish matter–free galaxies kind, and reveal new particulars in regards to the nature of darkish matter.

However different scientists are skeptical that there’s sufficient proof to help this backstory. “If that is true, I feel it could be actually thrilling. I simply don’t assume the bar has been met,” says astronomer Michelle Collins of the College of Surrey in Guildford, England.

In 2018, Yale College astronomer Pieter van Dokkum and colleagues reported a dwarf galaxy with no darkish matter (SN: 3/28/18). The invisible, mysterious substance is often detectable in galaxies through its gravitational results on stars. When a second darkish matter–free dwarf galaxy was discovered within the neighborhood in 2019, it raised an apparent query: How did the 2 oddball galaxies kind? Darkish matter is mostly thought to kind the inspiration of all galaxies, gravitationally attracting the fuel that finally types stars. So some course of will need to have separated the darkish matter from the galaxies’ fuel.

Scientists have beforehand seen darkish matter and regular matter separate on a really massive scale within the Bullet Cluster, which shaped when two clusters of galaxies rammed into each other (SN: 8/23/06). Different researchers had proposed that one thing related would possibly occur with colliding dwarf galaxies, what van Dokkum and colleagues name “bullet dwarfs.”

In such a collision, the dwarf galaxies’ ethereal darkish matter would proceed on unperturbed, as a result of the darkish matter doesn’t work together with different matter. However the fuel from the 2 galaxies would slam collectively, finally forming a number of clumps that will every develop into its personal galaxy, freed from darkish matter.

Now, van Dokkum and colleagues say that the bullet dwarf concept explains the 2 beforehand reported darkish matter–free galaxies — and several other different galaxies close by. The 2 galaxies are shifting away from one another as if they’d come from the identical spot, the researchers say. What’s extra, the 2 galaxies are a part of a sequence of 11 galaxies aligned in a row, a construction that would have shaped within the aftermath of a bullet dwarf collision.

image showing 11 galaxies with inset images of the individual galaxies
Two galaxies discovered to be freed from darkish matter, NGC 1052-DF2 and NGC 1052-DF4, are a part of a line of 11 galaxies complete (proven in insets). That linear association of galaxies might have been produced by an historical collision of two progenitor galaxies.P. van Dokkum et al/Nature 2022Two galaxies discovered to be freed from darkish matter, NGC 1052-DF2 and NGC 1052-DF4, are a part of a line of 11 galaxies complete (proven in insets). That linear association of galaxies might have been produced by an historical collision of two progenitor galaxies.P. van Dokkum et al/Nature 2022

“It’s tremendous satisfying to lastly have an evidence for these bizarre objects,” van Dokkum says.

However, Collins says, “there could possibly be far more accomplished to make it convincing.” For instance, she says, the scientists didn’t measure the distances of all of the galaxies from Earth. Meaning a few of the galaxies could possibly be a lot farther away than others, and it could possibly be a coincidence that the galaxies look like lined up from our viewpoint.  

And the researchers haven’t but measured the velocities of all of the galaxies within the path or decided whether or not these galaxies are additionally lacking their darkish matter, which might assist verify whether or not the situation is right.

Different scientists are extra optimistic. “The origin story may be very believable for my part,” says astrophysicist Eun-jin Shin of Seoul Nationwide College in South Korea. Shin cowrote a perspective article on the invention with astrophysicist Ji-hoon Kim, additionally of Seoul Nationwide College, that was additionally revealed in Nature.

Pc simulations carried out by Shin, Kim and others have proven that bullet dwarfs can produce such darkish matter–free galaxies. If confirmed, the bullet dwarf concept might assist pin down darkish matter’s properties, particularly whether or not darkish matter interacts with itself (SN: 4/5/18).

Van Dokkum and colleagues are planning further measurements that would verify or refute the case. However to this point, he says, “It has, to me, the ring of reality.”

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