Astronomers have spotted a massive disk galaxy, not unlike our own, that formed 12.5 billion years ago when our 13.8 billion-year-old universe was only a tenth of its current age. But according to what scientists know about galaxy formation, this one has no business being in the distant universe.
This discovery is challenging how astronomers think about galaxy formation in the early universe.
It’s known as Galaxy DLA0817g, but astronomers nicknamed it the Wolfe Disk after late astronomer Arthur M. Wolfe, former doctoral advisor to three of the study’s four authors. It represents the most distant rotating disk galaxy they have ever observed, thanks to the Atacama Large Millimeter/submillimeter Array of telescopes in Chile known as ALMA.
According to their observations, the galaxy’s disk has a mass of 70 billion times that of our sun. It’s also rotating at 170 miles per second, which is similar to our Milky Way galaxy. But galaxies with stable, well-formed disks, like the Milky Way, formed gradually and appeared later in the universe’s timeline, with some dated to 6 billion years after the Big Bang.
In the early days after the Big Bang, the universe was largely a blank slate. Eventually, this was followed by galaxy formation that was pretty messy. Small galaxies merged and crashed together along with hot gas clumps.
“Most galaxies that we find early in the universe look like train wrecks because they underwent consistent and often ‘violent’ merging,” said Marcel Neeleman, lead study author and postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany, in a statement. “These hot mergers make it difficult to form well-ordered, cold rotating disks like we observe in our present universe.”
The study published this week in the journal Nature.
So how did a well-formed rotating disk galaxy appear during this turbulent period? This galaxy formed and grew, researchers concluded, in a different way, known as cold-mode accretion.
Much of what astronomers know about galaxy formation is based on hierarchy. In the beginning, halo-like structures of dark matter, a large, unseen component of the universe known by its effect on surrounding matter, drew in gas. Mergers created something larger where star formation was possible, and eventually, a galaxy was born.
The gas drawn in by the dark matter halos was heated by the collisions, and it would form a disk once it cooled — which could take place over billions of years.
But in the cold scenario, much cooler gas is drawn into a new galaxy and allows for quicker formation of a disk.
“We think the Wolfe Disk has grown primarily through the steady accretion of cold gas,” said J. Xavier Prochaska, study coauthor and professor of astronomy and astrophysics of the University of California, Santa Cruz, in a statement. “Still, one of the questions that remains is how to assemble such a large gas mass while maintaining a relatively stable, rotating disk.”
The researchers also used data from the Hubble Space Telescope and the National Science Foundation’s Karl G. Jansky Very Large Array of radio antennae in New Mexico to understand what kind of star formation was occurring in the galaxy.
“The star formation rate in the Wolfe Disk is at least 10 times higher than in our own galaxy,” explained Prochaska. “It must be one of the most productive disk galaxies in the early universe.”
Neeleman and his colleagues first spotted the Wolfe Disk using ALMA in 2017 when light from a quasar passed through hydrogen gas around the galaxy and revealed it. A quasar, which looks a bit like a star through a telescope, is actually a remote object that emits a large amount of energy likely powered by matter falling on a black hole at the center of a galaxy. The light helped them identify this normal galaxy, rather than the direct light emitted by extremely bright galaxies.
Otherwise, distant galaxies are hard to observe because they’re so faint. But this “absorption” of light method using quasars can happen when the telescopes, galaxy and quasar are in alignment, which is rare — unless galaxies like this were more common in the early universe.
“The fact that we found the Wolfe Disk using this method, tells us that it belongs to the normal population of galaxies present at early times,” Neeleman said. “When our newest observations with ALMA surprisingly showed that it is rotating, we realized that early rotating disk galaxies are not as rare as we thought and that there should be a lot more of them out there. Thanks to ALMA, we now have unambiguous evidence that they occur as early as 1.5 billion years after the Big Bang.”
Future research and observation is needed to understand how common this cold method of galaxy formation was in the early universe.
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The cleanest pocket of air on Earth? It's in the Southern Ocean, between Tasmania and Antarctica – National Post
The cleanest air on Earth lies in a pocket of sky between Tasmania and Antarctica, scientists say.
A team of researchers at Colorado State University conducted a bioaerosol study of the Southern Ocean from Tasmania to Antarctica — the first of its kind — and drew air samples at the marine boundary level, where the atmosphere meets the ocean surface.
“We were able to use the bacteria in the air over the Southern Ocean (SO) as a diagnostic tool to infer key properties of the lower atmosphere,” microbian ecologist Thomas Hill, from Colorado State University, told Science Alert.
Via modelling and analysis, the team noted that the samples were free of aerosol particles — a sure indicator of human activity, like fossil fuel burning, agriculture and fertilizer production — blown in from other parts of the world. The samples were also split into latitudinal zones, so that the team could observe how the air changed as they moved further south.
Via wind patterns, airborne microorganisms can travel vast distances. However, the bacterial make-up of the samples suggested that the closer they were taken to Antarctica, the cleaner they became. This suggests that aerosols from distant land masses and human activities are not travelling south into Antarctic air.
Instead, the samples appear to be composed of microorganisms from the ocean and little else.
“It suggests that the SO (Southern Ocean) is one of very few places on Earth that has been minimally affected by anthropogenic activities,” Hill said.
The results counter similar studies that were carried out in oceans in the subtropics and the Northern Hemisphere, which concluded that most microbes came from upwind continents.
The Strawberry Moon Eclipse May Be Visible Over Metro Vancouver This Week – 604 Now
Metro Vancouver is in for a treat this week, as we’ll be able to see the Strawberry Moon eclipse shine over the city this Friday.
Named after the red summer fruit, this phenomenon is June’s full moon – or otherwise called the Hot Moon or Rose moon.
This particular moon, however, kicks off 2020’s “eclipse season,” and will be visible during the moonrise and moonset.
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You’ll just have to be ready at either 5:30 am or 8 pm, Friday, to see the eclipse over Metro Vancouver.
So, will you be checking it out this week?
Friday, June 5th is also the day of the second George Floyd protest, happening downtown.
For more Vancouver stories, head to our News section.
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