A “giant arc” 1.6 Billion Light Years across thought to contain hundreds of thousands of galaxies

24th June, 2021.      //   Space Travel  // 

What is the limit of how large something can be before it becomes too large?

A newly discovered crescent of galaxies spanning 3.3 billion lightyears is one of the world’s largest known structures, challenging some of astronomers’ most fundamental ideas about the universe.

The Giant Arc is a massive structure made up of galaxies, galactic clusters, and a lot of gas and dust. It is 9.2 billion light-years away and covers nearly one-fifth of the observable universe.

What is the limit of how big is too huge, you might ask?

Alexia Lopez, a doctorate candidate in cosmology at the University of Central Lancashire (UCLan) in the United Kingdom, told Live Science that the discovery was “serendipitous.” Lopez was utilizing the light from roughly 120,000 quasars — faraway brilliant centres of galaxies where supermassive black holes are eating matter and spewing forth energy — to create maps of things in the night sky.

As this light travels through matter between us and the quasars, it is absorbed by various components, leaving unmistakable fingerprints that can provide valuable information to researchers. Lopez used the marks left by magnesium to measure the distance between the material and the intervening gas and dust, as well as its position in the night sky.

The quasars, Lopez explained, work “like spotlights in a dark room, illuminating this intervening stuff.”

A structure began to develop in the midst of the cosmic maps. Lopez described it as “kind of a hint of a vast arc.” “I recall exclaiming, ‘Oh, look at this,’ to Roger [Clowes].”

Clowes, her PhD adviser at UCLan, suggested doing more research to be sure it wasn’t a coincidence or a data trick. The researchers found that there was less than a 0.0003 percent chance that the Giant Arc wasn’t real after running two distinct statistical analyses. On 7th June , they presented their findings at the American Astronomical Society’s 238th virtual meeting.

However, the discovery, which will go down in history as one of the most significant events in the universe, calls into question a fundamental belief about the universe. Astronomers have long held to the cosmological principle, which holds that stuff is more or less evenly distributed throughout space at the biggest sizes.

The Giant Arc dwarfs other massive structures like the Sloan Great Wall and the South Pole Wall, which are both overshadowed by much greater cosmic phenomena. Clowes told Live Science, “There have been a lot of large-scale structures revealed over the years.” “You have to ask if they’re compatible with the cosmological principle because they’re so big.”

The fact that such massive objects have gathered in specific areas of the cosmos suggests that matter isn’t spread uniformly throughout the universe.

However, Lopez noted, the present conventional model of the cosmos is based on the cosmological principle. “If we don’t find it to be true, perhaps we might look at another set of theories or principles.”

Lopez is unsure what those theories might entail, though she did suggest that the prospect of altering gravity on the largest scales, is an hypothesis that has recently gained traction among a tiny but vocal group of scientists.
The cosmological principle should mandate a theoretical limit on the size of cosmic things, according to Daniel Pomarède, a cosmographer from Paris-Saclay University in France who co-discovered the South Pole Wall.

Pomarède told Live Science that some studies suggest that structures should grow to a particular size and then stop growing. “Instead, we keep uncovering bigger and greater structures,” says the researcher. He isn’t ready though, to abandon the cosmological principle, which has been utilized in universe models for over a century. “To predict it will be replaced by something else would be pretty brave,” he remarked.