One Cosmic Mystery Illuminates Another, As Fast Radio Burst Intercepts A Galactic Halo
“Although scientists have studied [Fast Radio Bursts] intensely since their discovery, their origins remain mysterious. Meanwhile, an estimated 2 trillion galaxies populate our observable Universe. With incredibly large distances for FRBs to traverse, each one risks passing through an intervening galaxy. Giving off multiple pulses of under 40 microseconds apiece, FRB 181112 became the first burst to intercept a galactic halo.”
Where do fast radio bursts come from? Recent studies have demonstrated that they’re associated with host galaxies, but we don’t understand how they work, why some of them repeat, or why the pulse durations are so variable.
What about galactic halos: how much gas is in them? What is the gas temperature, density, magnetization, etc.? These are big questions about galaxies in general that we don’t have a general picture of. If only there were some way to learn more.
How about luck? We got lucky, in November of 2018, when for the first time a fast radio burst passed through a foreground galaxy’s halo. What did we learn? Come get (and see) the full story!
This Is What The Milky Way’s Magnetic Field Looks Like
“The Milky Way’s gas, dust, stars and more create fascinating, measurable structures. Subtracting out all the foregrounds yields the cosmic background signal, which possesses tiny temperature imperfections. But the galactic foreground isn’t useless; it’s a map unto itself. All background light gets polarized by these foregrounds, enabling the reconstruction of our galaxy’s magnetic field.”
Have you ever wondered what our galaxy’s magnetic field looks like? As long as we restrict ourselves to looking in the type of light that human eyes can see, the optical portion of the spectrum, we’re extremely limited as far as what we can infer. However, if we move on to data from the microwave portion of the spectrum, and in particular we look at the data that comes from the polarization of background light (and the foreground light directly), we should be able to reconstruct our galaxy’s magnetic fields to the best precision ever. The Planck satellite, in addition to mapping the CMB to better precision than ever before, has enabled us to do exactly that.
Even though there are still some small questions and uncertainties, you won’t want to miss these incredible pictures that showcase just how far we’ve come!
A black hole is the most powerful astronomical object, because it can say the n word.
This Is Why Every Galaxy Doesn’t Have The Same Amount Of Dark Matter
“It isn’t the properties of one or two galaxies that will be the ultimate test of dark matter, however. Whether these galaxies are generic dwarf galaxies or our first examples of dark matter-free galaxies isn’t the point; the point is that there are hundreds of billions of these dwarf galaxies out there that are presently below the limits of what’s observable, detectable, or having their properties measured. When we get there, especially in the distant Universe and in post-interaction environments, we can fully expect to truly find this yet-unconfirmed population of galaxies.
If dark matter is real, it must be separable from normal matter, and that works both ways. We’ve already found the dark matter-rich galaxies out there, as well as isolated intergalactic plasma. But dark matter-free galaxies? They might be right around the corner, and this is why everybody is so excited!”
When the Universe was first born, everything was uniform. There was dark matter and normal matter everywhere, in the same 5-to-1 ratio in all structures. But then the Universe had to go and get messy. It formed stars and galaxies of different masses and sizes, and that’s where the trouble started. In large, massive galaxies, even cataclysms like supernovae or active supermassive black holes don’t eject very much normal matter. But in small galaxies, significant amounts of normal matter can get ejected, upping that ratio to dozens or event hundreds to one. That ejected matter doesn’t just go away, but can itself, at least in theory, form dark matter-free galaxies. Where are we in our understanding of galaxies, dark matter, and gravitation?
It’s just a small piece of the puzzle, but this explains why not every galaxy has the same 5-to-1 ratio you might naively expect!
Scientists Discover The Loneliest, Most Isolated Galaxy In The Entire Universe
“The spirals and ellipticals in our backyard showed us, a century ago, that the Milky Way wasn’t alone. Even earlier astronomers still had copious bright galaxies they could observe with their telescopes. By measuring the speeds and distances of these galaxies, we discovered the expanding Universe. Without them, we might never have understood our cosmic origins: the hot Big Bang. Unfortunately, not every observer in the Universe gets so lucky.”
When we look out at the Universe, we see stars, galaxies, and galaxy clusters grouped together and aligned in a great cosmic web. Together, they make up the large-scale structure of the Universe. Observing these distant galaxies is what led us to our current scientific knowledge of all that’s out there, including about the Big Bang, dark matter, and many other fascinating properties.
But between these vast clumps of structure are enormous cosmic voids, containing very low numbers of galaxies. One such void is some 200 million light-years in diameter, and contains only one known galaxy in it: MCG+01-02-15, which is known as the loneliest galaxy in the Universe. If we lived there instead of in our Milky Way, we would not have discovered even a single galaxy beyond our own until we had reached 1960s-era levels of astronomical capabilities.
Come learn about the loneliest galaxy in the Universe, and see why we’re fortunate to be located here instead of there!
Galaxy Clusters Are Where Galaxies Like The Milky Way Go To Die
“When a galaxy enters a rich, massive cluster, it has to contend with two murderous factors. A single major merger can use up all the gas in both progenitor galaxies, leading to a red-and-dead elliptical galaxy. Even without one, the intracluster medium is rich in matter, and speeding through it can strip out a galaxy’s gas. Without that gaseous presence, new stars can no longer form.”
Here in our Local Group, our Milky Way forms stars at a low but steady rate, and will likely continue to do so for billions of years. It’s only our impending major merger with Andromeda that will use up all of our gas, and turn us into a giant elliptical without the capacity to form new stars. If we were more isolated, we could continue to form stars for trillions of years: many times the age of the Universe.
But if we were in a rich galaxy clusters, our demise would be not only certain, but much more rapid. Here’s the proof.
What Was It Like When The Milky Way Took Shape?
“The cosmic story that led to the Milky Way is one of constant evolution. We likely formed from hundreds or even thousands of smaller, early-stage galaxies that merged together. The spiral arms likely formed and were destroyed many times by interactions, only to re-form from the rotating, gas-rich nature of an evolving galaxy. Star formation occurred inside in waves, often triggered by minor mergers or gravitational interactions. And these waves of star-formation brought along increases in supernova rates and heavy metal enrichment. (Which sounds like everyone’s favorite after-school activity.)
These continuous changes are still occurring, and will come to a conclusion billions of years in the future, when all the galaxies of the Local Group have merged together. Every single galaxy has its own unique cosmic story, and the Milky Way is just one typical example. As grown up as we are, we’re still evolving.”
We normally think of events in the past of having occurred at a specific time. Star formation began in the Universe when it was 50-to-100 million years old. The first galaxies formed some ~200 million years after that. The Universe became transparent to visible light 550 million years after the Big Bang, and star formation reached its maximum between 2 and 3 billion years after the Big Bang.
But when did the Milky Way form?
That’s a silly question, as it turns out, because what we know as the Milky Way has been constantly evolving and growing over time. Had we come along billions of years ago, or were we to come along billions of years in the future, our galaxy would be unrecognizable to us.
Here’s the story of how the Milky Way took shape, and what it was like along every step of the way. You might be surprised!
This Is How We Will Discover The Most Distant Galaxy Ever
“Sometime in the distant past, likely when the Universe was less than 2% its current age, the very first galaxy of all formed when massive star clusters merged together, resulting in an unprecedented burst of star formation. The high-energy light from these stars struggles to escape, but the longer-wavelength light can penetrate farther through neutral atoms. The expansion of the Universe redshifts all the light, stretching it far beyond anything Hubble could potentially observe, but next-generation infrared telescopes should be able to catch it. And if we observe the right part of the sky, with the right instruments, for a sufficiently long time to reveal the right details about these objects, we’ll push back the cosmic frontier of the first galaxies even farther.
Somewhere, the most distant, first galaxy of all is out there, waiting to be discovered. As the 2020s approach, we can feel confident that we’ll not only shatter the current cosmic record-holder, but we know exactly how we’ll do it.”
13.8 billion years ago, our Universe as-we-know-it began with the hot Big Bang. There were no stars or galaxies back then; there weren’t even bound structures of any type. Everything was too energetic, and would immediately be destroyed by the unfathomably high temperatures and energies that every particle possessed. Yet, with time, the Universe expanded and cooled. Protons, nuclei, and neutral atoms formed; overdense regions gravitationally pulled-in mass and matter; stars were born, lived, died, and new stars were born in their aftermath. At some point, the first large star clusters merged together, passing a critical threshold and forming the first galaxy in the Universe.
That’s what we want to find. We’ve gone back to when the Universe was just 3% its present age, but that’s not enough. We must go father. We must find the first one. Here’s how we’ll do it.
The Brightest Galaxy In The Universe Is Surprisingly Young And Tiny
“In 2015, a new record was set for the brightest known galaxy, thanks to observations with the WISE telescope. Supermassive black holes power Extremely Luminous Infrared Galaxies. The brightest ones shine 10,000+ times as bright as our Milky Way.Although the Universe is just 10% of its current age and the galaxy is even smaller than ours, it outshines them all.”
I want you to close your eyes and imagine the Milky Way: a typical galaxy. Now, imagine a different galaxy, the brightest one you can think up. What does it look like? How do you imagine it?
Do you imagine something large, massive, with hundreds or even thousands of times as many stars? Do you imagine something that’s built itself up over billions of years? Well if that’s what you imagined, prepare to be shocked! The brightest ones of all are young, ultra-distant, and even smaller than our own galaxy!
Here’s the brightest galaxy in the Universe, which is turbulent, dusty, and looks nothing like you might expect!