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Category: cosmology – Page 226

Do supermassive black holes have friends? The nature of galaxy formation suggests that the answer is yes, and in fact, pairs of supermassive black holes should be common in the universe.

I am an astrophysicist and am interested in a wide range of theoretical problems in astrophysics, from the formation of the very first galaxies to the gravitational interactions of black holes, stars and even planets. Black holes are intriguing systems, and supermassive black holes and the dense stellar environments that surround them represent one of the most extreme places in our universe.

The supermassive black hole that lurks at the center of our galaxy, called Sgr A*, has a mass of about 4 million times that of our Sun. A black hole is a place in space where gravity is so strong that neither particles or light can escape from it. Surrounding Sgr A* is a dense cluster of stars. Precise measurements of the orbits of these stars allowed astronomers to confirm the existence of this supermassive black hole and to measure its mass. For more than 20 years, scientists have been monitoring the orbits of these stars around the supermassive black hole. Based on what we’ve seen, my colleagues and I show that if there is a friend there, it might be a second black hole nearby that is at least 100,000 times the mass of the Sun.

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A unique ultra-faint dwarf galaxy has been discovered on the outer fringes of the Andromeda Galaxy thanks to the discerning eyes of an amateur astronomer examining archival data processed by NSF’s NOIRLab’s Community Science and Data Center. The dwarf galaxy — Pegasus V — was revealed to contain very few heavier elements and is likely to be a fossil of the first galaxies in follow-up observations by professional astronomers using the International Gemini Observatory, a Program of NSF’s NOIRLab.

An unusual ultra-faint dwarf galaxy has been discovered on the edge of the Andromeda Galaxy with the help of several facilities of NSF’s NOIRLab. Called Pegasus V, the galaxy was first detected as part of a systematic search for Andromeda dwarfs coordinated by David Martinez-Delgado from the Instituto de Astrofísica de Andalucía, Spain, when amateur astronomer Giuseppe Donatiello discovered a curious ‘smudge’ in data in a DESI

The Dark Energy Spectroscopic Instrument (DESI) is a new instrument for conducting a spectrographic survey of distant galaxies that has been retrofitted onto the Mayall Telescope on top of Kitt Peak in the Sonoran Desert 55 miles distant from Tucson, Arizona. Its main components are a focal plane containing 5,000 fiber-positioning robots and a bank of spectrographs which are fed by the fibers. It enables an experiment to probe the expansion history of the Universe and the mysterious physics of dark energy.

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In Latin, nova means “new.” In astronomy, that refers to a temporary bright “star” in the night sky. But the causes of these brief but brilliant stars are varied.

Classical novae occur in a binary star system with a white dwarf and a star close enough together that the white dwarf pulls, or accretes, material from its companion. The material — mostly hydrogen — sits on the surface of the white dwarf until enough has been gathered to kick-start a nuclear fusion reaction, the same process that powers the Sun. As the hydrogen is converted into heavier elements, the temperature increases, which in turn increases the rate of hydrogen burning. At this point, the white dwarf experiences a runaway thermonuclear reaction, ejecting the unburnt hydrogen, which releases 10,000 to 100,000 times the energy our Sun emits in a year. Because the white dwarf remains intact after blowing away this excess, a stellar system can experience multiple classical novae.

Kilonovae occur when two compact objects, like binary neutron stars or a neutron star and a black hole, collide. These mergers, as their name suggest, are about 1,000 times brighter than a classical nova, but not as bright as a supernova, which is 10 to 100 times brighter than a kilonova.

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What would happen if you put a couple of physicists in a room with a rope, a box and a black hole? They might come up with a plan to power the Earth for centuries. Black holes aren’t something you come across every day. To make a black hole of your own, you’d have to squeeze a star ten times bigger than our Sun into a sphere the diameter of New York City.

Transcript and sources: https://whatif.show/what-if-we-could-harness-the-energy-of-a-black-hole/
Music: http://bit.ly/whatif-music.

Watch more what-if scenarios:
Planet Earth: https://www.youtube.com/watch?v=_-HhCwYD7rc&list=PLZdXRHYAVx…Yq9N9wyb2l.
The Cosmos: https://www.youtube.com/watch?v=gfuJyVkMH_g&list=PLZdXRHYAVx…wXNGYHmE8U
Technology: https://www.youtube.com/watch?v=CS3bBO05fpU&list=PLZdXRHYAVx…qSEB7kDdKO
Your Body: https://www.youtube.com/watch?v=QmXR46TrbA8&list=PLZdXRHYAVx…2ySsHj8GZO
Humanity: https://www.youtube.com/watch?v=fdCDQIyXGnw&list=PLZdXRHYAVx…t8zFxSCSvZ

Tweet us your what-if question to suggest an episode: https://twitter.com/WhatIfScience.

Continue reading “What If We Could Harness the Energy of a Black Hole?” | >

A lab in Tennesee that does research in neutron, nuclear and clean energy had to debunk the myth that they were somehow attempting to open portals to other dimensions. Though if I ever learned anything from popular science fiction, if a research lab says they aren’t opening portals to parallel universes, my instinct tells me that they are totally opening portals to other dimensions. So you can imagine why folks would be skeptical.

Research scientist Leah Broussard explains in the video above that the experiments they are doing at the Oak Ridge National Laboratory (which is managed by the US Department of Energy) aren’t exactly about building portals to other dimensions. Instead, they involved “looking for new ways that matter we know and understand, that makes up our universe, might interact with the dark matter that makes up the majority of our universe, which we don’t understand.”

Broussard also explains when a particle physicist says portal, they mean it in a figurative sense. All this talk of parallel universes came when her research was released and people started making connections to the Netflix show, Stranger Things. A show that, coincidentally, features kids stumbling across a shady government agency opening portals to other dimensions full of monsters, in the ’80s.

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What is time? Why is it so different from space? And where did it come from? Scientists are still stumped by these questions — but working harder than ever to answer them.

St. Augustine said of time, “If no one asks me, I know what it is. If I wish to explain to him who asks, I don’t know.” Time is an elusive concept: We all experience it, and yet, the challenge of defining it has tested philosophers and scientists for millennia.

It wasn’t until Albert Einstein that we developed a more sophisticated mathematical understanding of time and space that allowed physicists to probe deeper into the connections between them. In their endeavors, physicists also discovered that seeking the origin of time forces us to confront the origins of the universe itself.

What exactly is time, and how did it come into being? Did the dimension of time exist from the moment of the Big Bang, or did time emerge as the universe evolved? Recent theories about the quantum nature of gravity provide some unique and fantastic answers to these millennia-old questions.

Continue reading “The struggle to find the origins of time” | >

To solve a long-standing puzzle about how long a neutron can “live” outside an atomic nucleus, physicists entertained a wild but testable theory positing the existence of a right-handed version of our left-handed universe. They designed a mind-bending experiment at the Department of Energy’s Oak Ridge National Laboratory to try to detect a particle that has been speculated but not spotted. If found, the theorized “mirror neutron”—a dark-matter twin to the neutron—could explain a discrepancy between answers from two types of neutron lifetime experiments and provide the first observation of dark matter.

“Dark matter remains one of the most important and puzzling questions in science—clear evidence we don’t understand all matter in nature,” said ORNL’s Leah Broussard, who led the study published in Physical Review Letters.

Neutrons and protons make up an atom’s nucleus. However, they also can exist outside nuclei. Last year, using the Los Alamos Neutron Science Center, co-author Frank Gonzalez, now at ORNL, led the most precise measurement ever of how long free neutrons live before they decay, or turn into protons, electrons and anti-neutrinos. The answer—877.8 seconds, give or take 0.3 seconds, or a little under 15 minutes—hinted at a crack in the Standard Model of particle physics. That model describes the behavior of subatomic particles, such as the three quarks that make up a neutron. The flipping of quarks initiates neutron decay into protons.

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Special relativity famously dictates that no known object can travel faster than the speed of light in a vacuum – making it unlikely that humans will ever send spacecraft to explore beyond our local area of the Milky Way. However, new research by Erik Lentz at the University of Göttingen suggests there could be a way beyond this limit. The only catch is that his scheme requires vast amounts of energy and so may never actually be able to propel a spacecraft (Class. Quant. Grav. 38 075015).

Lentz proposes that conventional energy sources could arrange the structure of space–time in the form of a soliton – a robust singular wave. This soliton would act like a “warp bubble’”, contracting space in front of it and expanding space behind. Unlike objects within it, space–time itself can bend, expand or warp at any speed. A spacecraft contained in a hyperfast bubble could therefore arrive at its destination faster than light would in normal space without breaking any physical laws.

It had been thought that the only way to produce a warp drive was by generating vast amounts of negative energy – perhaps by using some sort of undiscovered exotic matter or by manipulating dark energy. To get around this problem, Lentz constructed an unexplored geometric structure of space–time to derive a new family of solutions to Einstein’s general relativity equations called positive-energy solitons. Though Lentz’s solitons appear to conform to Einstein’s general theory of relativity and remove the need to create negative energy, space agencies will not be building warp drives any time soon, if ever. Part of the reason is that Lentz’s positive-energy warp drive requires a huge amount of energy. According to Lentz, a 100 m radius spacecraft would require the energy equivalent to “hundreds of times the mass of Jupiter”.

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Deep Follow-up of GW151226 — an ordinary binary or a low-mass ratio merger?

Now that we’ve been detecting gravitational waves.

Gravitational waves are distortions or ripples in the fabric of space and time. They were first detected in 2015 by the Advanced LIGO detectors and are produced by catastrophic events such as colliding black holes, supernovae, or merging neutron stars.

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