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Category: cosmology

Neil deGrasse Tyson explains the early state of our Universe. At the beginning of the universe, ordinary space and time developed out of a primeval state, where all matter and energy of the entire visible universe was contained in a hot, dense point called a gravitational singularity. A billionth the size of a nuclear particle.

While we can not imagine the entirety of the visible universe being a billion times smaller than a nuclear particle, that shouldn’t deter us from wondering about the early state of our universe. However, dealing with such extreme scales is immensely counter-intuitive and our evolved brains and senses have no capacity to grasp the depths of reality in the beginning of cosmic time. Therefore, scientists develop mathematical frameworks to describe the early universe.

Neil deGrasse Tyson also mentions that our senses are not necessarily the best tools to use in science when uncovering the mysteries of the Universe.

It is interesting to note that in the early Universe, high densities and heterogeneous conditions could have led sufficiently dense regions to undergo gravitational collapse, forming black holes. These types of Primordial black holes are hypothesized to have formed soon after the Big Bang. Going from one mystery to the next, some evidence suggests a possible Link Between Primordial Black Holes and Dark Matter.

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The most accurate distance measurement yet of ultra-diffuse galaxy (UDG) NGC1052-DF2 (DF2) confirms beyond any shadow of a doubt that it is lacking in dark matter. The newly measured distance of 22.1 +/-1.2 megaparsecs was obtained by an international team of researchers led by Zili Shen and Pieter van Dokkum of Yale University and Shany Danieli, a NASA Hubble Fellow at the Institute for Advanced Study.

“Determining an accurate distance to DF2 has been key in supporting our earlier results,” stated Danieli. “The new measurement reported in this study has crucial implications for estimating the physical properties of the galaxy, thus confirming its lack of dark matter.”

The results, published in Astrophysical Journal Letters on June 9, 2021, are based on 40 orbits of NASA’s Hubble Space Telescope, with imaging by the Advanced Camera for Surveys and a “tip of the red giant branch” (TRGB) analysis, the gold standard for such refined measurements. In 2019, the team published results measuring the distance to neighboring UDG NGC1052-DF4 (DF4) based on 12 Hubble orbits and TRGB analysis, which provided compelling evidence of missing dark matter. This preferred method expands on the team’s 2018 studies that relied on “surface brightness fluctuations” to gauge distance. Both galaxies were discovered with the Dragonfly Telephoto Array at the New Mexico Skies observatory.

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Learning the results sparked a moment of joyous celebration, Park says: high fives to everyone.

“This is some of the first experimental evidence of the formation of these collisionless shocks,” says plasma physicist Francisco Suzuki-Vidal of Imperial College London, who was not involved in the study. “This is something that has been really hard to reproduce in the laboratory.”

The team also discovered that electrons had been accelerated by the shock waves, reaching energies more than 100 times as high as those of particles in the ambient plasma. For the first time, scientists had watched particles surfing shock waves like the ones found in supernova remnants.

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It is hard for humans to wrap their heads around the fact that there are galaxies so far away that the light coming from them can be warped in a way that they actually experience a type of time delay. But that is exactly what is happening with extreme forms of gravitational lensing, such as those that give us the beautiful images of Einstein rings. In fact, the time dilation around some of these galaxies can be so extreme that the light from a single event, such as a supernova, can actually show up on Earth at dramatically different times. That is exactly what a team led by Dr. Steven Rodney at the University of South Carolina and Dr. Gabriel Brammer of the University of Copenhagen has found. Except three copies of this supernova have already appeared – and the team thinks it will show up again one more time, 20 years from now.

Finding such a supernova is important not just for its mind bending qualities – it also helps to settle an important debate in the cosmological community. The rate of expansion of the universe has outpaced the rate expected when calculated from the cosmic microwave background radiation. Most commonly, this cosmological conundrum is solved by invoking “dark energy” – a shadowy force that is supposedly responsible for increasing the acceleration rate. But scientists don’t actually know what dark energy is, and to figure it out they need a better model of the physics of the early universe.

One way to get that better model is to find an event that is actively being distorted through a gravitational lens. Importantly – the same event must show up at two separate, distinct times in order to provide input to a calculation about the ratio of the distance between the galaxy doing the lensing and the background galaxy that was the source of the event.

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Scientists are one step closer to solving general relativity’s biggest problem.

To do this, scientists used a new kind of observatory called LIGO (Laser Interferometer Gravitational-wave Observatory) that is fine-tuned to hunt for small disturbances in the fabric of spacetime caused by cosmic collisions, like black hole or neutron star mergers.

But this is only just the beginning of what LIGO can do, a team of international researchers reports in a new study published Thursday in the journal Science. Using new techniques to quantum cool LIGO’s mirrors, the team says that LIGO may soon also help them understand the quantum states of human-sized objects instead of just subatomic particles.

Vivishek Sudhir is a coauthor on the paper and assistant professor of mechanical engineering at the Massachusetts Institute of Technology. He tells Inverse that physicists have long theorized that gravity may be the culprit behind why large items don’t exhibit quantum behavior.

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Peer long enough into the heavens, and the Universe starts to resemble a city at night. Galaxies take on characteristics of streetlamps cluttering up neighborhoods of dark matter, linked by highways of gas that run along the shores of intergalactic nothingness.

This map of the Universe was preordained, laid out in the tiniest of shivers of quantum physics moments after the Big Bang launched into an expansion of space and time some 13.8 billion years ago.

Yet exactly what those fluctuations were, and how they set in motion the physics that would see atoms pool into the massive cosmic structures we see today is still far from clear.

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One of my favorite science fiction authors is/was Isaac Asimov (should we use the past tense since he is no longer with us, or the present tense because we still enjoy his writings?). In many ways Asimov was a futurist, but — like all who attempt to foretell what is to come — he occasionally managed to miss the mark.

Take his classic Foundation Trilogy, for example (before he added the two prequels and two sequels). On the one hand we have a Galactic Empire that spans the Milky Way with millions of inhabited worlds and quadrillions of people. Also, we have mighty space vessels equipped with hyperdrives that can convey people from one side of the galaxy to the other while they are still young enough to enjoy the experience.

On the other hand, in Foundation and Empire, when a message arrives at a spaceship via hyperwave for the attention of General Bel Riose, it’s transcribed onto a metal spool that’s placed in a message capsule that will open only to his thumbprint. Asimov simply never conceived of things like today’s wireless networks and tablet computers and suchlike.

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We live in the Milky Way Galaxy, which is a collection of stars, gas, dust, and a supermassive black hole at it’s very center. Our Galaxy is a spiral galaxy, which are rotating structures that are flat (disk-like) like a DVD when looked upon edge-on. There is also a bulge in the middle that consists of mostly old stars. When you look at a spiral galaxy face-on, you can see beautiful spiral arms where stars are being born. Our solar system is in the Orion arm, and we are about 25000 light years (2.5 × 1017 miles) from the very center of the Galaxy.

Schematic of the milky way credit: oglethorpe university.

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