The universe: Reading the future from the distant past

Cosmic Calendar - Wikipedia

Scientists work at SLAC and Stanford are combining experimental data and theory to understand how the universe formed and what its future holds. Here, clumps and filaments of dark matter (black areas) serve as the scaffolding for the formation of cosmic structures made of regular matter (bright areas), including stars, galaxies and galaxy clusters.

The Dark Energy Survey World Scientific

These are the fundamental questions "astrophysical archeologists" like Risa Wechsler want to answer. At the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) of Stanford and the Department of Energy's SLAC National Accelerator Laboratory, her team combines experimental data with theory in computer simulations that dig deeply into cosmic history and trace back how matter particles clumped together to form larger and larger structures in the expanding universe.

"Most of our calculations are done at KIPAC, and computing is a crucial aspect of the collaboration between SLAC and Stanford," says Wechsler, who is an associate professor of physics and of particle physics and astrophysics.

Wechsler's simulated journeys through spacetime use a variety of experimental data, including observations by the Dark Energy Survey (DES), which recently discovered a new set of ultra-faint companion galaxies of our Milky Way that are rich in what is known as dark matter. The gravitational pull from this invisible form of matter affects regular matter, which plays a crucial role in the formation and growth of galaxies.

Dark energy is another key ingredient shaping the universe: It inflates the universe like a balloon at an ever-increasing rate, but researchers don't know much about what causes the acceleration.


Two future projects will give Wechsler and other researchers new clues about the mysterious energy. The Dark Energy Spectroscopic Instrument (DESI), whose science collaboration she is leading, will begin in 2018 to turn two-dimensional images of surveys like DES into a three-dimensional map of the universe. The Large Synoptic Survey Telescope (LSST), whose ultrasensitive 3,200-megapixel digital eye is being assembled at SLAC, will start a few years later to explore space more deeply than any telescope before.

"Looking at faraway galaxies means looking into the past and allows us to measure how the growth and distribution of galaxies were affected by dark energy at different points in time," Wechsler says. "Over the past 10 years, we've made a lot of progress in refining our cosmological model, which describes many of the properties of today's universe very well. Yet, if future data caused this model to break down, it would completely change our view of the universe."

The current model suggests that the universe is fated to expand forever, turning into a darker and darker cosmos faster and faster, with galaxies growing farther and farther apart. But is this acceleration a constant or changing property of spacetime? Or could it possibly be a breakdown of our theory of gravity on the largest scales? More data will help researchers find an answer to these fundamental questions.

Other articles on the same theme:

What form does the atomic nucleus? New discovery may explain the mysteries of the Universe.

A new theory on the Creation of the Universe, disprove the Big Bang

The First Stars in the Universe could provide clues about Dark Matter

NOBEL PHYSICS 2016. Nobel Prize winners are David DJ. Thouless, F. M. Duncan Haldane and J. Michael Kosterlitz

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The above post is reprinted from materials provided by SLAC National Accelerator Laboratory. The original item was written by Manuel Gnida. Note: Materials may be edited for content and length.

Gas giants could have a layer of mysterious 'dark hydrogen' the third form of hydrogen new discovery

We've just found a third form of hydrogen

For the first time, scientists have successfully forced hydrogen into a state that exists between metal and gas - a form known as 'dark hydrogen' - that they say could occur naturally on gas giants like Jupiter.

If this is true, having the ability to study dark hydrogen in the lab might offer a greater insight into how gas giants expel heat and generate magnetic fields.

"This dark hydrogen layer was unexpected and inconsistent with what modelling research had led us to believe about the change from hydrogen gas to metallic hydrogen inside of celestial objects," said team member Alexander Goncharov, from the Carnegie Institute of Science in Washington, DC. "This observation would explain how heat can easily escape from gas giant planets like Saturn."

Scientists claim to have turned hydrogen into a metal photo: Science News for Students

Although hydrogen is the most abundant element in the Universe, we still have a lot to learn about it. Scientists already know that there are two forms of hydrogen - the molecular hydrogen we're used to here on Earth, and metallic hydrogen inside the core of giant planets, which has been squeezed until it becomes liquid metal capable of conducting electricity with no resistance.

Now they've created a third form of hydrogen in the lab, somewhere between the two.

Since the new dark hydrogen exists somewhere between a metal and a gas, the researchers think it could actually sit between the molecular hydrogen on the surface of Jupiter (and planets like it) and the metallic hydrogen of the core beneath.

That's because this intermediate hydrogen phase doesn't reflect or transmit visible light, but can transmit infrared radiation (or heat). It can also transmit electricity, albeit very poorly, which could explain how a magnetic field can be generated around the planet.

Alexander Goncharov - Wikipedia

This is quite important because, right now, we just don't know all that much about how hydrogen reacts to extreme temperature and pressure. To find out, the team simulated conditions to match up to 1.5 million times atmospheric pressure and up to 10,000 degrees Fahrenheit (5,538 degrees Celsius).

The Very Large Array (VLA) in Socorro, New Mexico. Photograph by Dave Download Scientific Diagram

As Michael Franco reports for Gizmag, the team recreated these conditions by using a laser-heated diamond anvil cell to put the hydrogen under extreme pressure. The device uses two diamond tips to exert force way beyond what we experience on Earth, making it more like the pressures found on Jupiter.

Earlier this year, researchers at the University of Edinburgh in the UK managed to produce a metallic form of hydrogen by putting it under 3.25 million times the pressure of Earth's atmosphere, another step forward in gaining insight into how the giant planets of the Solar System work.

As well as being the most abundant element in the Universe (accounting for three-quarters of its overall mass), it's also the simplest, with a single electron in each atom. Under high pressure, hydrogen molecules begin to separate into single atoms, with the atoms' electrons showing signs of behaving like those of a metal.

These new findings come only a month after researchers working with the Very Large Array in New Mexico detected hydrogen in a galaxy some 5 billion light-years away.

The study has been published in Physical Review Letters.