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Category: cosmology – Page 292

A new map of dark matter made using artificial intelligence reveals hidden filaments of the invisible stuff bridging galaxies.

The map focuses on the local universe — the neighborhood surrounding the Milky Way. Despite being close by, the local universe is difficult to map because it’s chock full of complex structures made of visible matter, said Donghui Jeong, an astrophysicist at Pennsylvania State University and the lead author of the new research.

“We have to reverse engineer to know where dark matter is by looking at galaxies,” Jeong told Live Science.

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We know dark matter exists because we can observe its effects on all the stuff that’s swirling around in the universe. Scientists estimate that about 27% of the universe is made of dark matter (68% is dark energy, and the last 5% is ordinary matter and energy). The questions on everyone’s mind: Where exactly is all that elusive stuff located? And how is it distributed throughout the universe?

An international project of over 400 scientists called the Dark Energy Survey is working on answering them. It has just released the largest and most detailed map of dark matter in the universe—with some unexpected findings that don’t yet neatly align with ideas in physics that date all the way back to Albert Einstein and his theory of general relativity.

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Related: The 12 strangest objects in the universe

The most plausible explanation for the survival of G2 is that it’s more than just an ordinary gas cloud. Its hidden superpower? A star or two could be tucked inside the cloud, and the gravity of that star kept the whole structure intact during its passage near the black hole.

But there’s another, more radical explanation: Perhaps, the supermassive black hole isn’t really a black hole. Perhaps, it’s a fuzzy clump of dark matter.

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Five years on from the first discovery of gravitational waves, an international team of scientists, including from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), are continuing the hunt for new discoveries and insights into the Universe. Using the super-sensitive, kilometer-sized LIGO detectors in the United States, and the Virgo detector in Europe, the team have witnessed the explosive collisions of black holes and neutron stars. Recent studies, however, have been looking for something quite different: the elusive signal from a solitary, rapidly-spinning neutron star.

Take a star similar in size to the Sun, squash it down to a ball about twenty kilometers across — roughly the distance from Melbourne airport to the city center — and you’d get a neutron star: the densest object in the known Universe. Now set your neutron star spinning at hundreds of revolutions per second and listen carefully. If your neutron star isn’t perfectly spherical, it will wobble about a bit, and you’ll hear a faint “humming” sound. Scientists call this a continuous gravitational wave.

So far, these humming neutron stars have proved elusive. As OzGrav postdoctoral researcher Karl Wette from the Australian National University explains: Imagine you’re out in the Australian bush listening to the wildlife. The gravitational waves from black hole and neutron star collisions we’ve observed so far are like squawking cockatoos — loud and boisterous, they’re pretty easy to spot!

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What does quark-gluon plasma—the hot soup of elementary particles formed a few microseconds after the Big Bang—have in common with tap water? Scientists say it’s the way it flows.

A new study, published today in the journal SciPost Physics, has highlighted the surprising similarities between , the first matter thought to have filled the early Universe, and water that comes from our tap.

The ratio between the viscosity of a , the measure of how runny it is, and its density, decides how it flows. Whilst both the viscosity and density of are about 16 orders of magnitude larger than in water, the researchers found that the ratio between the viscosity and density of the two types of fluids are the same. This suggests that one of the most exotic states of matter known to exist in our universe would flow out of your tap in much the same way as water.

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A new map of dark matter in the local universe reveals several previously undiscovered filamentary structures connecting galaxies. The map, developed using machine learning by an international team including a Penn State astrophysicist, could enable studies about the nature of dark matter as well as about the history and future of our local universe.

Dark matter is an elusive substance that makes up 80% of the universe. It also provides the skeleton for what cosmologists call the cosmic web, the large-scale structure of the universe that, due to its gravitational influence, dictates the motion of galaxies and other cosmic material. However, the distribution of local dark matter is currently unknown because it cannot be measured directly. Researchers must instead infer its distribution based on its gravitational influence on other objects in the universe, like galaxies.

“Ironically, it’s easier to study the distribution of dark matter much further away because it reflects the very distant past, which is much less complex,” said Donghui Jeong, associate professor of astronomy and astrophysics at Penn State and a corresponding author of the study. “Over time, as the large-scale structure of the universe has grown, the complexity of the universe has increased, so it is inherently harder to make measurements about dark matter locally.”

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Astronomers have discovered an exceedingly old star at the edge of our galaxy that seems to have formed only a few million years after the Big Bang – and what they are learning from it could affect their understanding of the birth of the universe.

In a study published last week, researchers found the star during an astronomical survey of the southern sky with a technique called narrowband photometry, which measures the brightness of distant stars in different wavelengths of light and can reveal stars that have low levels of heavy elements.

They then studied the star – known by its survey number as SPLUS J210428.01−004934.2, or SPLUS J2104−0049 for short – with high-resolution spectroscopy to determine its chemical makeup.

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Regardless of size, all black holes experience similar accretion cycles, a new study finds.

On September 9, 2018, astronomers spotted a flash from a galaxy 860 million light years away. The source was a supermassive black hole about 50 million times the mass of the sun. Normally quiet, the gravitational giant suddenly awoke to devour a passing star in a rare instance known as a tidal disruption event. As the stellar debris fell toward the black hole, it released an enormous amount of energy in the form of light.

Researchers at MIT, the European Southern Observatory, and elsewhere used multiple telescopes to keep watch on the event, labeled AT2018fyk. To their surprise, they observed that as the supermassive black hole consumed the star, it exhibited properties that were similar to that of much smaller, stellar-mass black holes.

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