cosmology (10)

Our Galaxy's Water Worlds...

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This artist’s concept shows a hypothetical planet covered in water around the binary star system of Kepler-35A and B. The composition of such water worlds has fascinated astronomers and astrophysicists for years. (Image by NASA/JPL-Caltech.)

 

Topics: Astronomy, Astrobiology, Astrophysics, Cosmology, Exoplanets

Out beyond our solar system, visible only as the smallest dot in space with even the most powerful telescopes, other worlds exist. Many of these worlds, astronomers have discovered, may be much larger than Earth and completely covered in water — basically ocean planets with no protruding land masses. What kind of life could develop on such a world? Could a habitat like this even support life?

A team of researchers led by Arizona State University (ASU) recently set out to investigate those questions. And since they couldn’t travel to distant exoplanets to take samples, they decided to recreate the conditions of those water worlds in the laboratory. In this case, that laboratory was the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility at the DOE’s Argonne National Laboratory.

What they found — recently published in Proceedings of the National Academy of Sciences — was a new transitional phase between silica and water, indicating that the boundary between water and rock on these exoplanets is not as solid as it is here on Earth. This pivotal discovery could change the way astronomers and astrophysicists have been modeling these exoplanets, and inform the way we think about life evolving on them.

Dan Shim, associate professor at ASU, led this new research. Shim leads ASU’s Lab for Earth and Planetary Materials and has long been fascinated by the geological and ecological makeup of these distant worlds. That composition, he said, is nothing like any planet in our solar system — these planets may have more than 50% water or ice atop their rock layers, and those rock layers would have to exist at very high temperatures and under crushing pressure.

Beneath the surface of our galaxy’s water worlds, Andre Salles, Argonne National Laboratory

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Axions...

 

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Image Source: Axion particle spotted in solid-state crystal, Max Planck Society, Phys.org

 

 

Topics: Cosmology, Dark Matter, Particle Physics, Quantum Mechanics, Standard Model

A team of physicists has made what might be the first-ever detection of an axion.

Axions are unconfirmed, hypothetical ultralight particles from beyond the Standard Model of particle physics, which describes the behavior of subatomic particles. Theoretical physicists first proposed the existence of axions in the 1970s in order to resolve problems in the math governing the strong force, which binds particles called quarks together. But axions have since become a popular explanation for dark matter, the mysterious substance that makes up 85% of the mass of the universe, yet emits no light.

If confirmed, it’s not yet certain whether these axions would, in fact, fix the asymmetries in the strong force. And they wouldn’t explain most of the missing mass in the universe, said Kai Martens, a physicist at the University of Tokyo who worked on the experiment. These axions, which appear to be streaming out of the sun, don’t act like the “cold dark matter” that physicists believe fills halos around galaxies. And they would be particles newly brought into being inside the sun, while the bulk of the cold dark matter out there appears to have existed unchanged for billions of years since the early universe.*

Still, it sure seems like there was a signal. It turned up in a dark underground tank of 3.5 tons (3.2 metric tons) of liquid xenon—the XENON1T experiment based at the Gran Sasso National Laboratory in Italy. At least two other physical effects could explain the XENON1T data. However, the researchers tested several theories and found that axions streaming out of our sun were the likeliest explanation for their results.

Physicists who weren’t involved in the experiment have not reviewed the data as of the announcement at 10 a.m. ET today (June 17). Reporters were briefed on the finding before the announcement, but data and paper on the find were not made available.

Live Science shared the XENON collaboration’s press release with two axion experts.

Physicists Announce Potential Dark Matter Breakthrough, Rafi Letzter, Live Science/Scientific American

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More Alike Than Different...

 

Topics: Astrophysics, Atomic Physics, Cosmology, Philosophy

We are more alike than different. The atoms in our bodies are the same forged in distant stars; Carl Sagan said we are "made of star stuff."

Then: we evolve under ultraviolet light at degree inclinations on the globe, thereby changing the prominence of Melanin in our epidurals. Due to war and conquests, we craft a narrative of what is godly, who is "divine" and who is deviant. Good and evil has a hue or light and darkness. And thus, we craft the seeds of our own self-destruction from ignorance, hubris, racism, snobbery and xenophobia.

Star stuff should be better behaved.

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Missing Link...

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A cosmic homicide in action, with a wayward star being shredded by the intense gravitational pull of a black hole that contains tens of thousands of solar masses in an artist's impression obtained by Reuters April 2, 2020. NASA-ESA/D. Player/Handout via REUTERS.

 

Topics: Astrophysics, Black Holes, Cosmology, General Relativity, Hubble


Using data from the Hubble Space Telescope and two X-ray observatories, the researchers determined that this black hole is more than 50,000 times the mass of our sun and located 740 million light years from Earth in a dwarf galaxy, one containing far fewer stars than our Milky Way.

Black holes are extraordinarily dense objects possessing gravitational pulls so powerful that not even light can escape.

This is one of the few “intermediate-mass” black holes ever identified, being far smaller than the supermassive black holes that reside at the center of large galaxies but far larger than so-called stellar-mass black holes formed by the collapse of massive individual stars.

“We confirmed that an object that we discovered originally back in 2010 is indeed an intermediate-mass black hole that ripped apart and swallowed a passing star,” said University of Toulouse astrophysicist Natalie Webb, a co-author of the study published this week in Astrophysical Journal Letters.

 

Astronomers spot 'missing link' black hole - not too big and not too small
Will Dunham, Reuters Science

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Geodes...

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(Just_Super/iStock)

 

Topics: Black Holes, Cosmology, Dark Energy, Einstein, General Relativity, Gravity


A fifty-year-old hypothesis predicting the existence of bodies dubbed Generic Objects of Dark Energy (GEODEs) is getting a second look in light of a proposed correction to assumptions we use to model the way our Universe expands.

If this new version of a classic cosmological model is correct, some black holes could hide cores of pure dark energy, pushing our Universe apart at the seams.

University of Hawaii astrophysicist Kevin Croker and mathematician Joel Weiner teamed up to challenge the broadly accepted notion that when it comes to the Universe's growing waistline, its contents are largely irrelevant.

"For 80 years, we've generally operated under the assumption that the Universe, in broad strokes, was not affected by the particular details of any small region," said Croker.

"It is now clear that general relativity can observably connect collapsed stars – regions the size of Honolulu – to the behavior of the Universe as a whole, over a thousand billion billion times larger."

Not only could this alternative interpretation of fundamental physics change how we understand the Universe's expansion, but we might need to also consider how that growth might affect compact objects like the cores of collapsing stars.

 

Black Holes May Hide Cores of Pure Dark Energy That Keep The Universe Expanding
Mike McCrae, Science Alert

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Easy-Peasy...

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(Image: © Shutterstock)

 

Topics: Black Holes, Cosmology, General Relativity, Wormholes


Everybody wants a wormhole. I mean, who wants to bother traveling the long-and-slow routes throughout the universe, taking tens of thousands of years just to reach yet another boring star? Not when you can pop into the nearest wormhole opening, take a short stroll, and end up in some exotic far-flung corner of the universe.

There's a small technical difficulty, though: Wormholes, which are bends in space-time so extreme that a shortcut tunnel forms, are catastrophically unstable. As in, as soon as you send a single photon down the hole, it collapses faster than the speed of light.

But a recent paper, published to the preprint journal arXiv on July 29, has found a way to build an almost-steady wormhole, one that does collapse but slowly enough to send messages — and potentially even things — down it before it tears itself apart. All you need are a couple of black holes and a few infinitely long cosmic strings.

In principle, building a wormhole is pretty straightforward. According to Einstein's Theory of General Relativity, mass and energy warp the fabric of space-time. And a certain special configuration of matter and energy allows the formation of a tunnel, a shortcut between two otherwise distant portions of the universe.

Unfortunately, even on paper, those wormholes are fantastically unstable. Even a single photon passing through the wormhole triggers a catastrophic cascade that rips the wormhole apart. However, a healthy dose of negative mass — yes, that's matter but with an opposite weight — can counteract the destabilizing effects of regular matter trying to pass through the wormhole, making it traversable.

OK, matter with negative mass doesn't exist, so we need a new plan.

 

Physicists Just Released Step-by-Step Instructions for Building a Wormhole
Paul Sutter, Live Science

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The Gravity of the Matter...

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Testing Einstein: conceptual image showing S0-2 (the blue and green object) as it made its closest approach to the supermassive black hole at the center of the Milky Way. The huge gravitational field of the black hole is illustrated by the distorted grid in space–time. (Courtesy: Nicolle R Fuller/National Science Foundation)

 

Topics: Astrophysics, Black Holes, Cosmology, Einstein, General Relativity


A key aspect of Einstein’s general theory of relativity has passed its most rigorous test so far. An international team led by Tuan Do and Andrea Ghez at the University of California, Los Angeles confirmed the Einstein equivalence principle (EEP) by analyzing the redshift of light from the star S0-2 at its closest approach to Sagittarius A* – the supermassive black hole at the center of the Milky Way. The study combined over 20 years of existing spectroscopic and astrometric measurements of S0-2 with the team’s own observations.

Since Einstein first proposed his general theory of relativity in 1915, the idea has stood up to intense experimental scrutiny by explaining the behaviors of gravitational fields in the solar system, the dynamics of binary pulsars, and gravitational waves emitted by mergers of black holes.

In 2018, the GRAVITY collaboration carried out a particularly rigorous test – observing S0-2 at its closest approach to Sagittarius A* in its 16-year orbit.

As expected, the GRAVITY astronomers observed a characteristic relativistic redshift in light from S0-2. This redshift is a lengthening of the wavelength of the light and arises from both the motion of the star (the Doppler effect) and the EEP. The latter is a consequence of general relativity and predicts a redshift in light from a source that is in a gravitational field such as that of a supermassive black hole.

 

Einstein’s general theory of relativity tested by star orbiting a black hole
Sam Jarman, Physics World

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There Be Monsters...

Two views of galaxy Markarian 1216. The red image on the left shows X-ray observations conducted by NASA's Chandra X-Ray Observatory, and the yellowish image on the right is composed of optical observations taken by the Hubble Space Telescope. The brighter colors at the center of the Chandra image represent the increased density of hot gas in the galaxy's core.

 

Topics: Astronomy, Astrophysics, Cosmology, Dark Matter


X-ray observations of a peculiar galaxy deep within the constellation Hydra (the Sea Serpent) have revealed more dark matter at its core than expected.

The galaxy is almost as old as the universe itself, representatives from NASA's Chandra X-Ray Observatory said in a statement published Monday (June 3). This celestial body, Markarian 1216, went through a different evolution than typical galaxies and is home to stars that are within 10% of the age of the universe.

To study the dark matter within this compact, elliptically shaped galaxy about 295 million light- years from Earth, researchers conducted new observations with the Chandra spacecraft. Markarian 1216 is packed with more dark matter in its core than researchers expected, according to their findings published June 1.

 

Ancient Galaxy in the 'Sea Serpent' Has More Dark Matter Than Expected, Doris Elin Salazar, Space,com

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Event Horizon...

Scientists have obtained the first-ever image of a black hole — at center of the galaxy M87. Credit: Event Horizon Telescope collaboration et al.

 

Topics: Astrophysics, Black Holes, Cosmology, Einstein


(Yesterday) At six simultaneous press conferences around the globe, astronomers on Wednesday announced they had accomplished the seemingly impossible: taking a picture of a black hole, a cosmic monster so voracious that light itself cannot escape its clutches.

This historic feat, performed by the Event Horizon Telescope (EHT)—a planet-spanning network of radio observatories—required more than a decade of effort. The project’s name refers to a black hole’s most defining characteristic, an “event horizon” set by the object’s mass and spin beyond which no infalling material, including light, can ever return.

“We have taken the first picture of a black hole,” the EHT project’s director, Sheperd Doeleman, said in a news release. “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”

The image unveils the shadowy face of a 6.5-billion-solar-mass supermassive black hole at the core of Messier 87 (M87), a large galaxy some 55 million light-years from Earth in the Virgo galaxy cluster. Such objects are a reflection of Einstein’s theory of general relativity, which predicts that only so much material can be squeezed into any given volume before the overwhelming force of its accumulated gravity causes a collapse—a warp in the fabric of spacetime that swallows itself. Left behind is an almost featureless nothingness that, for lack of better terms, scientists simply call a black hole.

"Gargantua," special effects from the movie, Interstellar, 2014 (Kip Thorne et al guessed right):
Image Source: HDQ Walls dot com

 

At Last, a Black Hole’s Image Revealed, Lee Billings, Scientific American

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Sagittarius A...

Getty Images


Topics: Astronomy, Astrophysics, Black Holes, Cosmology, Einstein


They've captured our imaginations for decades, but we've never actually photographed a black hole before – until now.

Next Wednesday, at several press briefings around the world, scientists will apparently unveil humanity's first-ever photo of a black hole, the European Space Agency said in a statement. Specifically, the photo will be of "Sagittarius A," the supermassive black hole that's at the center of our Milky Way galaxy.

But aren't black holes, well, black, and thus invisible, so none of our telescopes can "see" them? Yes – therefore the image we're likely to see will be of the "event horizon," the edge of the black hole where light can't escape. [1]

*****


Next week, a collection of countries around the world are going to make a big announcement, and no one is sure exactly what it’s going to be. However, there are some possibilities, and the most exciting one is that they are about to reveal the first-ever photograph of the event horizon of a black hole.

Taking a photo of a black hole is not an easy task. Not only are black holes famous for not letting any light escape, even the nearest known black holes are very far away. The specific black hole astronomers wanted to photograph, Sagittarius A*, lies at the center of our galaxy 25,000 light-years away.

The international Event Horizon Telescope project announced its plan to photograph Sagittarius A* back in 2017, and they enlisted some of the world’s biggest telescopes to help out. The researchers used half a dozen radio telescopes, including the ALMA telescope in Chile and the James Clerk Maxwell telescope in Hawaii, to stare at Sagittarius A* over the past two years.

And while a picture of the black hole itself is impossible, the EHT astronomers were really aiming at the next best thing: the event horizon, the border of the black hole beyond which not even light can escape. At the event horizon, gravity is so strong that light will orbit the black hole like planets orbit stars, and our telescopes should be able to pick that up. [2]
 

1. 'Something no human has seen before': The first-ever photograph of a black hole will likely be unveiled next week, Doyle Rice, USA Today
2. We Might Be About to See the First Ever Photo of a Black Hole, Avery Thomson, Popular Mechanics

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