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Category: cosmology

New observations of young stellar object Elias 2–27 confirm gravitational instabilities and planet-forming disk mass as key to formation of giant planets.

A team of scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) to study the young star Elias 2–27 have confirmed that gravitational instabilities play a key role in planet formation, and have for the first time directly measured the mass of protoplanetary disks using gas velocity data, potentially unlocking one of the mysteries of planet formation. The results of the research are published today (June 17, 2021) in two papers in The Astrophysical Journal.

Protoplanetary disks — planet-forming disks made of gas and dust that surround newly formed young stars — are known to scientists as the birthplace of planets. The exact process of planet formation, however, has remained a mystery. The new research, led by Teresa Paneque-Carreño — a recent graduate of the Universidad de Chile and PhD student at the University of Leiden and the European Southern Observatory, and the primary author on the first of the two papers — focuses on unlocking the mystery of planet formation.

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For those not in the loop, the Kardashev Scale is a system of measurement invented by Soviet astronomer Nikolai Kardashev in 1964. It quantifies how advanced a civilization is according to how much energy they’re able to harness.

Type 1 civilizations have harnessed 100% of the accessible energy of their own planet. Type 2 has harnessed 100% of the accessible energy in their solar system. Type 3 has harnessed 100% of the accessible energy in their galaxy. There is no official Type 4 but it is conceivable that eventually a civilization could harness 100% of the accessible energy in the universe, and Type 5, which has harnessed all the accessible energy in the multiverse.

That’s some heavy stuff, well beyond the scope of this article. The public’s focus on near term manned spaceflight efforts these days belies a problem with our priorities. Grand, ambitious projects like settling the Moon and Mars grab our attention, while there’s still much left to be done on Earth.

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Observing the secrets of the universe’s “Dark Ages” will require capturing ultra-long radio wavelengths—and we can’t do that on Earth.

The universe is constantly beaming its history to us. For instance: Information about what happened long, long ago, contained in the long-length radio waves that are ubiquitous throughout the universe, likely hold the details about how the first stars and black holes were formed. There’s a problem, though. Because of our atmosphere and noisy radio signals generated by modern society, we can’t read them from Earth.

That’s why NASA is in the early stages of planning what it would take to build an automated research telescope on the far side of the moon. One of the most ambitious proposals would build the Lunar Crater Radio Telescope, the largest (by a lot) filled-aperture radio telescope dish in the universe. Another duo of projects, called FarSide and FarView, would connect a vast array of antennas—eventually over 100000, many built on the moon itself and made out of its surface material—to pick up the signals. The projects are all part of NASA’s Institute for Advanced Concepts (NIAC) program, which awards innovators and entrepreneurs with funding to advance radical ideas in hopes of creating breakthrough aerospace concepts. While they are still hypothetical, and years away from reality, the findings from these projects could reshape our cosmological model of the universe.

“With our telescopes on the moon, we can reverse-engineer the radio spectra that we record, and infer for the first time the properties of the very first stars,” said Jack Burns, a cosmologist at the University of Colorado Boulder and the co-investigator and science lead for both FarSide and FarView. “We care about those first stars because we care about our own origins—I mean, where did we come from? Where did the Sun come from? Where did the Earth come from? The Milky Way?”

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Dark matter may self-interact through a continuum of low-mass states. This happens if dark matter couples to a strongly-coupled nearly-conformal hidden sector. This type of theory is holographically described by brane-localized dark matter interacting with bulk fields in a slice of 5D anti-de Sitter space. The long-range potential in this scenario depends on a non-integer power of the spatial separation, in contrast to the Yukawa potential generated by the exchange of a single 4D mediator. The resulting self-interaction cross section scales like a non-integer power of velocity. We identify the Born, classical and resonant regimes and investigate them using state-of-the-art numerical methods. We demonstrate the viability of our continuum-mediated framework to address the astrophysical small-scale structure anomalies. Investigating the continuum-mediated Sommerfeld enhancement, we demonstrate that a pattern of resonances can occur depending on the non-integer power. We conclude that continuum mediators introduce novel power-law scalings which open new possibilities for dark matter self-interaction phenomenology.

A preprint version of the article is available at ArXiv.

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At the heart of almost every sufficiently massive galaxy there is a black hole whose gravitational field, although very intense, affects only a small region around the center of the galaxy. Even though these objects are thousands of millions of times smaller than their host galaxies, our current view is that the Universe can be understood only if the evolution of galaxies is regulated by the activity of these black holes, because without them the observed properties of the galaxies cannot be explained.

Theoretical predictions suggest that as these black holes grow they generate sufficient energy to heat up and drive out the gas within to great distances. Observing and describing the mechanism by which this energy interacts with galaxies and modifies their is therefore a basic question in present day Astrophysics.

With this aim in mind, a study led by Ignacio Martín Navarro, a researcher at the Instituto de Astrofísica de Canarias (IAC), has gone a step further and has tried to see whether the matter and energy emitted from around these black holes can alter the evolution, not only of the host galaxy, but also of the satellite galaxies around it, at even greater distances. To do this, the team has used the Sloan Digital Sky Survey, which allowed them to analyze the properties of the galaxies in thousands of groups and clusters. The conclusions of this study, started during Navarro’s stay at the Max Planck Institute for Astrophysics, are published today in Nature magazine.

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A ball of gas around the Milky Way’s black hole has sparked a new debate. Could it be a massive puff of dark matter?

The orbit of S2 and its stellar companions indicated that they were circling around a massive object, about 4 million times the mass of the Sun. Although astronomers could not directly see the object, they knew it could only be one thing.

By 1974, the object, eventually dubbed Sagittarius A*, was more or less solidified as your own local supermassive black hole. Since then, scientists have made several follow-up observations to reestablish the existence of this dark, lurking beast in the Milky Way — even turning one of the largest virtual telescopes in the world on it.

But not everyone seems to agree on the true nature of Sagittarius A*. A recent study claims that the black hole of our galaxy is not a black hole at all. Instead, it gives a more exotic take on physics that isn’t yet proven: that Sagittarius A* is an imposter, not a black hole but a massive, fluffy ball of fermionic dark matter.

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