Tag Archives: galaxies

Scientists Intrigued by Bridge of Dark Matter Inside Huge Galaxy Cluster

Posted on by

The mysterious dark matter

The Perseus cluster is a vast swirl of thousands of galaxies, all bound together by gravity. Famed for its unbelievable size — containing the mass of some 600 trillion suns — it also has a reputation for being one of the few "relaxed" galaxy clusters out there: it shows no signs of having undergone a powerful but disruptive merger with another galaxy, which is how these clusters typically grow. In a word, Perseus looks settled down and pretty stable.

But that may not be the case, according to an international team of astronomers. As detailed in a new study published in the journal Nature Astronomy, the astronomers have found a "bridge" of dark matter that leads to the center of the cluster, which they believe is the remnant of a massive object slamming into the galactic swirl billions of years ago. If this is evidence of a major merger, it'd mean that Perseus isn't so "relaxed" after all.

"This is the missing piece we've been looking for," said study coauthor James Jee, a physicist at University of California, Davis, in a statement about the work. "All the odd shapes and swirling gas observed in the Perseus cluster now make sense within the context of a major merger."

Dark matter is the invisible substance believed to account for around 80 percent of all mass in the universe. While we can't interact with dark matter, its gravity appears to be responsible for governing the shapes of the cosmos's largest structures, pulling "normal" matter together around "clumps" of itself to form the galaxies that we see.

To make the discovery, the astronomers sifted through data collected by the Subaru Telescope in Japan to look for signs of what's known as gravitational lensing. This occurs when the gravity of a massive object bends the light of more distant sources like a lens, magnifying our view of what lies behind it. 

By measuring how the light is being distorted, astronomers can infer traits about the object that's causing the lensing. This technique is known as weak gravitational lensing, and can only be used when there's a large number of galaxies that the distortion's incredibly subtle effects can be observed on. It's one of the primary ways that astronomers map the distribution of dark matter throughout the cosmos.

Using this technique, the astronomers found a dark matter clump located inside the Perseus cluster around 1.4 million light years away from its center, weighing a colossal 200 trillion solar masses (the entire Milky Way, for reference, weighs about 1.5 trillion solar masses). But the clump clearly was a highly disruptive intruder, because it left behind an enormous dark matter "bridge" linking it to the center of the cluster. According to the astronomers, it's as good as a sign of a collision between the clump and the cluster as it gets. And from simulations they performed, this epic merger occurred some five billion years ago — the echoes of which still affect Perseus' structure to this day.

"It took courage to challenge the prevailing consensus, but the simulation results from our collaborators and recent observations from the Euclid and XRISM space telescopes strongly support our findings," lead author HyeongHan Kim, an astronomer at Yonsei University in South Korea, said in the statement.

More on dark matter: Scientists Say Dark Matter May Be Giving Off a Signal

The post Scientists Intrigued by Bridge of Dark Matter Inside Huge Galaxy Cluster appeared first on Futurism.

Read this article:
Scientists Intrigued by Bridge of Dark Matter Inside Huge Galaxy Cluster

There’s Something Very Strange About Our Galaxy

Posted on by

Researchers have found that there's something highly unusual about the Milky Way, setting it apart from other galaxies.

Galactic Outlier

Researchers have found that there's something highly unusual about the Milky Way that sets it apart from galaxies which, on a surface level, appear similar.

As detailed in three recent papers published in The Astrophysical Journal, a team of researchers examined a mountain of data as part of the Satellites Around Galactic Analogs (SAGA) survey, which was dedicated to comparing the Milky Way to 101 other galaxies that are similar in mass.

The distinction is technical but significant, the researchers say: they found that the Milky Way has surprisingly few smaller satellite galaxies compared to its peers — and some of them have mysteriously stopped forming new stars.

"Now we have a puzzle," said Stanford astrophysics professor Risa Wechsler, who cofounded SAGA and coauthored all three papers, in a statement. "What in the Milky Way caused these small, lower-mass satellites to have their star formation quenched?"

Satellite Activity

The findings suggest our galaxy's evolutionary history is strikingly different, setting it apart from all the others — research that could also force scientists to reexamine how we understand the formation of galaxies.

"Our results show that we cannot constrain models of galaxy formation just to the Milky Way," said Wechsler. "We have to look at that full distribution of similar galaxies across the universe."

At the core of the researchers' findings is dark matter, the mysterious substance that scientists believe makes up 85 percent of the matter in the universe, but has yet to be directly observed. Researchers have previously found that massive halos of dark matter allow galaxies to form within them, creating gravitational forces strong enough for ordinary matter to clump together.

"Perhaps, unlike a typical host galaxy, the Milky Way has a unique combination of older satellites that have ceased star formation and newer, active ones... that only recently fell into the Milky Way's dark matter halo," Wechsler suggested.

When Wechsler and her colleagues examined 378 small satellite galaxies that orbit the 101 much larger galaxies like the Milky Way, they found that half the Milky Way's satellites were no longer forming stars, unlike most other galaxies, whose satellites were still active stellar factories.

It all raises an intriguing question: why is our galactic home different?

"To me, the frontier is figuring out what dark matter is doing on scales smaller than the Milky Way, like with the smaller dark matter halos that surround these little satellites," Wechsler said.

More on galaxy formation: This Ancient "Rebel" Galaxy Closely Mirroring the Milky Way Has Astronomers Freaked Out

The post There's Something Very Strange About Our Galaxy appeared first on Futurism.

Originally posted here:
There's Something Very Strange About Our Galaxy