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Category: physics

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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Researchers at the Flatiron Institute’s Center for Computational Astrophysics published a paper last week that just might explain a mysterious gap in planet sizes beyond our solar system. Planets between 1.5 and 2 times Earth’s radius are strikingly rare. This new research suggests that the reason might be because planets slightly larger than this, called mini-Neptunes, lose their atmospheres over time, shrinking to become ‘super-Earths’ only slightly larger than our home planet. These changing planets only briefly have a radius the right size to fill the gap, quickly shrinking beyond it. The implication for planetary science is exciting, as it affirms that planets are not static objects, but evolving and dynamic worlds.

Exoplanet research is a very young field. As recently as 1992, no one had ever seen a planet beyond our solar system. Today, we’ve discovered more than 4700 of them, and that number is growing rapidly due to the efforts of dedicated planet-hunting space telescopes like Kepler (now defunct) and its successor, TESS. We’ve suddenly gained an enormous new sample size of planets to study, beyond the eight planets (sorry Pluto) that orbit around our sun.

Kepler, TESS, and other planet hunters have discovered brand new types of planets, like so-called ‘hot-Jupiters,’ large gas giants that orbit very close to their star. These were among the first exoplanets observed because their large size made them easy to find, and their small, fast orbital periods meant we could see them pass in front of their star more than once in a short period of time (some hot-Jupiters have a year that lasts only a few Earth days).

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This is how the future is made.

Sailing through the smooth waters of vacuum, a photon of light moves at around 300 thousand kilometers (186 thousand miles) a second. This sets a firm limit on how quickly a whisper of information can travel anywhere in the Universe.

While this law isn’t likely to ever be broken, there are features of light which don’t play by the same rules. Manipulating them won’t hasten our ability to travel to the stars, but they could help us clear the way to a whole new class of laser technology.

Physicists have been playing hard and fast with the speed limit of light pulses for a while, speeding them up and even slowing them to a virtual stand-still using various materials like cold atomic gases, refractive crystals, and optical fibers.

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An international research team analyzed a database of more than 1000 supernova explosions and found that models for the expansion of the Universe best match the data when a new time dependent variation is introduced. If proven correct with future, higher-quality data from the Subaru Telescope and other observatories, these results could indicate still unknown physics working on the cosmic scale.

Edwin Hubble’s observations over 90 years ago showing the expansion of the Universe remain a cornerstone of modern astrophysics. But when you get into the details of calculating how fast the Universe was expanding at different times in its history, scientists have difficulty getting theoretical models to match observations.

To solve this problem, a team led by Maria Dainotti (Assistant Professor at the National Astronomical Observatory of Japan and the Graduate University for Advanced Studies, SOKENDAI in Japan and an affiliated scientist at the Space Science Institute in the U.S.A.) analyzed a catalog of 1048 supernovae which exploded at different times in the history of the Universe. The team found that the theoretical models can be made to match the observations if one of the constants used in the equations, appropriately called the Hubble constant, is allowed to vary with time.

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A University of California San Diego engineering professor has solved one of the biggest mysteries in geophysics: What causes deep-focus earthquakes?

These mysterious earthquakes originate between 400 and 700 kilometers below the surface of the Earth and have been recorded with magnitudes up to 8.3 on the Richter scale.

Xanthippi Markenscoff, a distinguished professor in the Department of Mechanical and Aerospace Engineering at the UC San Diego Jacobs School of Engineering, is the person who solved this mystery. Her paper “Volume collapse instabilities in deep earthquakes: a shear source nucleated and driven by pressure” appears in the Journal of the Mechanics and Physics of Solids.

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The findings could lead to faster, more secure memory storage, in the form of antiferromagnetic bits.

When you save an image to your smartphone, those data are written onto tiny transistors that are electrically switched on or off in a pattern of “bits” to represent and encode that image. Most transistors today are made from silicon, an element that scientists have managed to switch at ever-smaller scales, enabling billions of bits, and therefore large libraries of images and other files, to be packed onto a single memory chip.

But growing demand for data, and the means to store them, is driving scientists to search beyond silicon for materials that can push memory devices to higher densities, speeds, and security.

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If you are a space enthusiast, there is some good news for you. In a new research, that could possibly open doors to many unknown aspects of the Universe, researchers have detected a resonant “hum” produced by the gravitational waves in the Universe. Experts say this can be imagined as a gravitational wave background of the Universe.

This hum of the Universe was reportedly detected by the North American Nanohetz Observatory for Gravitational Waves (NANOGrav), and the findings of the research was published in The Astrophysical Journal Letters.

In a report, ScienceAlert said this gravitational wave background can be imagined as “something like the ringing left behind by massive events throughout our Universe’s history”.

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