Cosmic microwave background radiation.

12 Feb 2021 {Just now in social media.]
Isabelle Dumé

The new metamaterial tiles in an advanced cryogenic facility. Credit: Eric Sucar/Penn Today.

Tiles made of metamaterials could make ground-based telescopes far more sensitive to the cosmic microwave background radiation [CMBR] that forms the “afterglow” of the Big Bang.

Cosmic microwave background radiation. Stephen Hawking Center for Theoretical Cosmology U, Cambridge (UK).

The polyurethane-and-carbon tiles, which work by sharply reducing the reflection and scattering of stray light, are now being installed in the millimetre-wave telescopes at Simons Observatory in Chile and could also be incorporated into upgrades at other facilities.

The cosmic microwave background (CMB) is the remnant of electromagnetic radiation released around 380 000 years after the Big Bang, when nuclei and electrons first combined to form atoms and space became transparent to light. The Simons Observatory is designed to measure directional variations or anisotropies in the polarization of this radiation.

LBL The Simons Array in the Atacama in Chile, altitude 5,200 m (17,100 ft) with the 6 meter Atacama Cosmology Telescope.

Evidence for certain types of anisotropies would strongly support the theory of cosmic inflation, which states that the universe underwent a period of extremely rapid expansion just 10-35 s after the Big Bang, increasing its volume by a factor of up to 108 within a fraction of a second.

Inflation

Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

Lamda Cold Dark Matter Accerated Expansion of The universe http scinotions.com the-cosmic-inflation-suggests-the-existence-of-parallel-universes
Alex Mittelmann, Coldcreation

Alan Guth’s notes:

Controlling stray light at cryogenic temperatures

The detectors in modern ground-based millimetre-wave telescopes like ones at the Simons Observatory operate at cryogenic temperatures, which enhances their sensitivity by reducing their intrinsic thermal or electronic noise. Over the past few decades, detector technology has advanced far enough that thermal noise is now less of a limiting factor than noise from stray light. This light, which reflects off the side walls of the cryogenically-cooled detectors instead of following the main optical path in the devices, can degrade the image the detector produces through effects known as “ghosting” and “glinting”, as well as reducing the detector’s overall sensitivity.

To control this stray light, telescope designers need materials that absorb millimetre wavelengths at the ultralow operating temperatures of the telescope’s detectors. Finding such materials has proved challenging because most materials developed for cryogenic temperatures have high indices of refraction, and therefore reflect and scatter significant amounts of light. Meanwhile, lower-refractive-index materials, such as those found in commercial microwave absorbers, cannot easily be employed in cryogenic environments.

Wedge-shaped modular tiles

A team led by Jeff McMahon at the University of Chicago(US) and Mark Devlin at the University of Pennsylvania(US) supported by the Simons Foundation(US) has now developed a way of controlling stray light using a wedge-shaped tile made from a microwave-absorbing metamaterial. Metamaterials are artificially engineered structures that can be designed in ways that give them properties – such as a negative refractive index – that are rare or nonexistant in natural materials.

The new metamaterial is based on carbon particles loaded with 25% polyurethane by mass. While the bulk of this composite efficiently absorbs light in the microwave region, its surface is highly reflective, so the researchers coated it with an antireflective pyramidal-shaped structure.

When combined with the bulk material, which absorbs almost all incoming photons, this antireflective surface makes the metamaterial tiles highly efficient at suppressing signals from stray light, say study lead authors Zhilei Xu and Grace Chesmore. The tiles’ optical properties remain intact at cryogenic temperatures just above absolute zero.

The researchers made their tiles using injecting moulding, a low-cost technique that easily scales up for mass production. The tiles’ modular nature also means that, unlike conventional painted surfaces, any damage can be fixed simply by replacing the affected tiles. While the shape of the tiles is tailored to the geometry of the Simons Observatory, other geometries, such as flat square tiles, are also possible and would exhibit similar optical performance, the researchers say.

Members of the team, who report their work in Applied Optics, now plan to use this technology in other telescopes. “These include the CMB-S4, the Fred Young Submillimeter Telescope (FYST) and the Cosmology Large Angular Scale Surveyor (CLASS),” Xu and Chesmore tell Physics World.

CMB-S4 is the next-generation ground-based cosmic microwave background experiment.
With 21 telescopes at the South Pole and in the Chilean Atacama desert surveying the sky with 550,000 cryogenically-cooled superconducting detectors for 7 years, CMB-S4 will deliver transformative discoveries in fundamental physics, cosmology, astrophysics, and astronomy.
CMB-S4 is supported by the Department of Energy Office of Science and the National Science Foundation.

Fred Young Submillimeter Telescope, to be installed at the summit of Cerro Chajnantor in the Atacama Desert of northern Chile, Altitude 5612 m (18412 ft).

Cosmology Large Angular Scale Surveyor- an array of microwave telescopes at a high-altitude site in the Atacama Desert of Chile as part of the Parque Astronómico de Atacama at more than 5000 meters altitude.

See the full article here .

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We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.

From U Hawaii at Manoa

via

phys.org

September 1, 2020

The universe is 7% of its current age at the bottom, 24% in the middle, and the universe today is displayed at the top. Credit: Volker Springel and the Max-Planck-Institute for Astrophysics.

Astronomers have known for two decades that the expansion of the universe is accelerating, but the physics of this expansion remains a mystery. Now, a team of researchers at the University of Hawai’i at Mānoa have made a novel prediction—the dark energy responsible for this accelerating growth comes from a vast sea of compact objects spread throughout the voids between galaxies. This conclusion is part of a new study published in The Astrophysical Journal.

In the mid-1960s, physicists first suggested that stellar collapse should not form true black holes, but should instead form Generic Objects of Dark Energy (GEODEs). Unlike black holes, GEODEs do not ‘break’ Einstein’s equations with singularities. Instead, a spinning layer surrounds a core of dark energy. Viewed from the outside, GEODEs and black holes appear mostly the same, even when the “sounds” of their collisions are measured by gravitational wave observatories.

Because GEODEs mimic black holes, it was assumed they moved through space the same way as black holes. “This becomes a problem if you want to explain the accelerating expansion of the universe,” said UH Mānoa Department of Physics and Astronomy research fellow Kevin Croker, lead author of the study. “Even though we proved last year that GEODEs, in principle, could provide the necessary dark energy, you need lots of old and massive GEODEs. If they moved like black holes, staying close to visible matter, galaxies like our own Milky Way would have been disrupted.”

Croker collaborated with UH Mānoa Department of Physics and Astronomy graduate student Jack Runburg, and Duncan Farrah, a faculty member at the UH Institute for Astronomy and the Physics and Astronomy department, to investigate how GEODEs move through space. The researchers found that the spinning layer around each GEODE determines how they move relative to each other. If their outer layers spin slowly, GEODEs clump more rapidly than black holes. This is because GEODEs gain mass from the growth of the universe itself. For GEODEs with layers that spin near the speed of light, however, the gain in mass becomes dominated by a different effect and the GEODEs begin to repel each other. “The dependence on spin was really quite unexpected,” said Farrah. “If confirmed by observation, it would be an entirely new class of phenomenon.”

The team solved Einstein’s equations under the assumption that many of the oldest stars, which were born when the universe was less than 2 percent of its current age, formed GEODEs when they died. As these ancient GEODEs fed on other stars and abundant interstellar gas, they began to spin very rapidly. Once spinning quickly enough, the GEODEs’ mutual repulsion caused most of them to ‘socially distance’ into regions that would eventually become the empty voids between present-day galaxies.

This study supports the position that GEODEs can solve the dark energy problem while remaining in harmony with different observations across vast distances. GEODEs stay away from present-day galaxies, so they do not disrupt delicate star pairs counted within the Milky Way. The number of ancient GEODEs required to solve the dark energy problem is consistent with the number of ancient stars. GEODEs do not disrupt the measured distribution of galaxies in space because they separate away from luminous matter before it forms present-day galaxies. Finally, GEODEs do not directly affect the gentle ripples in the afterglow of the Big Bang, because they are born from dead stars hundreds of millions of years after the release of this cosmic background radiation.

Cosmic Background Radiation per ESA/Planck

The researchers were cautiously optimistic about their results. “It was thought that, without a direct detection of something different than a Kerr [Black Hole] signature from LIGO-Virgo [gravitational wave observatories], you’d never be able to tell that GEODEs existed,” said Farrah. Croker added, “but now that we have a clearer understanding of how Einstein’s equations link big and small, we’ve been able to make contact with data from many communities, and a coherent picture is beginning to form.”

According to Runburg, whose primary research interest is unrelated to GEODEs, “the most exciting consequence, for me, is that previously disconnected communities of researchers now have common ground. When different communities work together, the whole always becomes something greater than the sum of the parts.”

See the full article here .

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Please help promote STEM in your local schools.

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U Hawaii 2.2 meter telescope, Mauna Kea, Hawaii, USA

The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth.

Keck Observatory, two 10 meter telescopes operated by Caltech and the University of California, Maunakea Hawaii USA, altitude 4,207 m (13,802 ft).

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Pann-STARS 1 Telescope, U Hawaii, situated at Haleakala Observatories on the island of Maui near the summit of Haleakala in Hawaii, USA, altitude 3,052 m (10,013 ft).

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