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Category: cosmology – Page 306

A new type of maser made from periodically driven xenon atoms can detect low frequency magnetic fields far better than any previous magnetometer, according to scientists in China and Germany. The researchers believe their device is ready for use in a proposed gravitational wave search and might in future be used to find hypothetical dark matter particles.

Masers are the microwave-wavelength equivalent of lasers and their extreme frequency stability allows them to make invaluable contributions to atomic clocks, radio telescopes and several other areas of physics. In a traditional maser – as in a traditional laser – the masing action occurs between two energy levels in an atomic or molecular gain medium confined in a cavity. As electromagnetic radiation bounces back and forth in the cavity, photons whose frequency is resonant with the energy difference between the two levels are repeatedly emitted and absorbed by the atoms. Eventually, a “population inversion” with more atoms in the upper level is achieved, and stimulated emission from these atoms produces a highly monochromatic beam of microwave radiation.

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What is the origin of black holes and how is that question connected with another mystery, the nature of dark matter? Dark matter comprises the majority of matter in the Universe, but its nature remains unknown.

Multiple gravitational wave detections of merging black holes have been identified within the last few years by the Laser Interferometer Gravitational-Wave Observatory (LIGO), commemorated with the 2017 physics Nobel Prize to Kip Thorne, Barry Barish, and Rainer Weiss. A definitive confirmation of the existence of black holes was celebrated with the 2020 physics Nobel Prize awarded to Andrea Ghez, Reinhard Genzel and Roger Penrose. Understanding the origin of black holes has thus emerged as a central issue in physics.

Surprisingly, LIGO has recently observed a 2.6 solar-mass black hole candidate (event GW190814, reported in Astrophysical Journal Letters 896 (2020) 2, L44). Assuming this is a black hole, and not an unusually massive neutron star, where does it come from?

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For decades, researchers assumed the cosmic rays that regularly bombard Earth from the far reaches of the galaxy are born when stars go supernova — when they grow too massive to support the fusion occurring at their cores and explode.

Those gigantic explosions do indeed propel atomic particles at the speed of light great distances. However, new research suggests even supernovae — capable of devouring entire solar systems — are not strong enough to imbue particles with the sustained energies needed to reach petaelectronvolts (PeVs), the amount of kinetic energy attained by very high-energy cosmic rays.

And yet cosmic rays have been observed striking Earth’s atmosphere at exactly those velocities, their passage marked, for example, by the detection tanks at the High-Altitude Water Cherenkov (HAWC) observatory near Puebla, Mexico. Instead of supernovae, the researchers posit that star clusters like the Cygnus Cocoon serve as PeVatrons — PeV accelerators — capable of moving particles across the galaxy at such high energy rates.

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TOWARDS a METAMATERIALLY-BASED ANALOGUE SENSOR FOR TELESCOPE EYEPIECES jeremy batterson.

(NB: Those familiar with photography or telescopy can skip over the “elements of a system,” since they will already know this.)

In many telescopic applications, what is desired is not a more magnified image, but a brighter image. Some astronomical objects, such as the Andromeda galaxy or famous nebulae like M42 are very large in apparent size, but very faint. If the human eye could see the Andromeda galaxy, it would appear four times wider than the Moon. The great Orion nebula M42 is twice the apparent diameter of the Moon.

Astrophotographers have an advantage over visual astronomers in that their digital sensors can be wider than the human pupil, and thus can accommodate larger exit pupils for brighter images.

The common three-factor determination of brightness of a photograph (aperture, ISO, and shutter speed) should actually be five-factor, including what is often left out since it had already been inherently designed into a system: magnification and exit pupil. The common factors are.

Elements of a system: 1 )Aperture. As aperture increases, the light gain of a system increases by the square of increased aperture, so a 2-inch diameter entrance pupil aperture has four times gain over a 1-inch diameter entrance pupil and so on.

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How can you possibly use simulations to reconstruct the history of the entire universe using only a small sample of galaxy observations? Through big data, that’s how.

Theoretically, we understand a lot of the physics of the history and evolution of the universe. We know that the universe used to be a lot smaller, denser, and hotter in the past. We know that its expansion is accelerating today. We know that the universe is made of very different things, including galaxies (which we can see) and dark matter (which we can’t).

We know that the largest structures in the universe have evolved slowly over time, starting as just small seeds and building up over billions of years through gravitational attraction.

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With the help of the European Southern Observatory’s Very Large Telescope (ESO ’s VLT), astronomers have discovered and studied in detail the most distant source of radio emission known to date. The source is a “radio-loud” quasar — a bright object with powerful jets emitting at radio wavelengths — that is so far away its light has taken 13 billion years to reach us. The discovery could provide important clues to help astronomers understand the early Universe.

Quasars are very bright objects that lie at the center of some galaxies and are powered by supermassive black holes. As the black hole consumes the surrounding gas, energy is released, allowing astronomers to spot them even when they are very far away.

The newly discovered quasar, nicknamed P172+18, is so distant that light from it has traveled for about 13 billion years to reach us: we see it as it was when the Universe was just around 780 million years old. While more distant quasars have been discovered, this is the first time astronomers have been able to identify the telltale signatures of radio jets in a quasar this early on in the history of the Universe. Only about 10% of quasars — which astronomers classify as “radio-loud” — have jets, which shine brightly at radio frequencies.[1].

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