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Category: cosmology – Page 297

A team led by astronomers at UC Santa Barbara have confirmed the existence of an elusive new type of supernova.

A worldwide team led by UC Santa Barbara scientists at Las Cumbres Observatory has discovered the first convincing evidence for a new type of stellar explosion — an electron-capture supernova. While they have been theorized for 40 years, real-world examples have been elusive. They are thought to arise from the explosions of massive super-asymptotic giant branch (SAGB) stars, for which there has also been scant evidence. The discovery, published in Nature Astronomy, also sheds new light on the thousand-year mystery of the supernova from A.D. 1054 that was visible all over the world in the daytime, before eventually becoming the Crab Nebula.

Historically, supernovae have fallen into two main types: thermonuclear and iron-core collapse. A thermonuclear supernova is the explosion of a white dwarf star after it gains matter in a binary star system. These white dwarfs are the dense cores of ash that remain after a low-mass star (one up to about 8 times the mass of the sun) reaches the end of its life. An iron core-collapse supernova occurs when a massive star — one more than about 10 times the mass of the sun — runs out of nuclear fuel and its iron core collapses, creating a black hole or neutron star. Between these two main types of supernovae are electron-capture supernovae. These stars stop fusion when their cores are made of oxygen, neon and magnesium; they aren’t massive enough to create iron.

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The Large Hadron Collider has a lot of tasks ahead of it. Next stop: investigating the Big Bang.

The truth is, we don’t really know because it takes huge amounts of energy and precision to recreate and understand the cosmos on such short timescales in the lab.

But scientists at the Large Hadron Collider (LHC) at CERN, Switzerland aren’t giving up.

Now our LHCb experiment has measured one of the smallest differences in mass between two particles ever, which will allow us to discover much more about our enigmatic cosmic origins.

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Submillimeter galaxies (SMGs) are a class of the most luminous, distant, and rapidly star-forming galaxies known and can shine brighter than a trillion Suns (about one hundred times more luminous in total than the Milky Way). They are generally hard to detect in the visible, however, because most of their ultraviloet and optical light is absorbed by dust which in turn is heated and radiates at submillimeter wavelengths—the reason they are called submillimeter galaxies. The power source for these galaxies is thought to be high rates of star formation, as much as one thousand stars per year (in the Milky Way, the rate is more like one star per year). SMGs typically date from the early universe; they are so distant that their light has been traveling for over ten billion years, more than 70% of the lifetime of the universe, from the epoch about three billion years after the big bang. Because it takes time for them to have evolved, astronomers think that even a billion years earlier they probably were actively making stars and influencing their environments, but very little is known about this phase of their evolution.

SMGs have recently been identified in galaxy protoclusters, groups of dozens of galaxies in the universe when it was less than a few billion years old. Observing massive SMGs in these distant protoclusters provides crucial details for understanding both their early evolution and that of the larger structures to which they belong. CfA astronomers Emily Pass and Matt Ashby were members of a team that used infrared and from the Spitzer IRAC and Gemini-South instruments, respectively, to study a previosly identified protocluster, SPT2349-56, in the era only 1.4 billion years after the big bang. The protocluster was spotted by the South Pole Telescope millimeter wavelengths and then observed in more detail with Spitzer, Gemini, and the ALMA submillimeter array.

The protocluster contains a remarkable concentration of fourteen SMGs, nine of which were detected by these optical and infrared observations. The astronomers were then able to estimate the , ages, and gas content in these SMGs, as well as their star formation histories, a remarkable acheievment for such distant objects. Among other properties of the protocluster, the scientists deduce that its total mass is about one trillion solar-masses, and its galaxies are making stars in a manner similar to star formation processes in the current universe. They also conclude that the whole ensemble is probably in the midst of a colossal merger.

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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.

In modern physics, antimatter is made up of elementary particles, each of which has the same mass as their corresponding matter counterparts — protons, neutrons and electrons — but the opposite charges and magnetic properties.

A collision between any particle and its anti-particle partner leads to their mutual annihilation, giving rise to various proportions of intense photons, gamma rays and neutrinos. The majority of the total energy of annihilation emerges in the form of ionizing radiation. If surrounding matter is present, the energy content of this radiation will be absorbed and converted into other forms of energy, such as heat or light. The amount of energy released is usually proportional to the total mass of the collided matter and antimatter, in accordance with Einstein’s mass–energy equivalence equation.

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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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