These Are The Most Distant Astronomical Objects In The Known Universe
“Astronomers have always sought to push back the viewable distance frontiers. More distant galaxies appear fainter, smaller, bluer, and less evolved overall. Individual planets and stars are only known relatively nearby, as our tools cannot take us farther. As the 2010s end, here are our presently known most distant astronomical objects.”
Have you ever wondered, as the 2010s draw to a close, what the status is of our most distant objects known? I don’t mean the most distant planet or star, but rather the most distant objects of all. How far away is the most distant supernova humanity has ever seen? What about the most distant X-ray jet, the most distant quasar, the most distant black hole, gamma-ray burst, or even the most distant galaxy of all?
It’s a fascinating chance to learn where we are today, because there’s an outstanding chance that with the new observatories we’ll see in the 2020s, each one of these existing records might fall!
What Is The Ultimate Fate Of The Loneliest Galaxy In The Universe?
“After an extraordinary amount of time has passed, googols of years or even more, the loneliest galaxy in the Universe will appear completely empty. No stars, stellar remnants, planetary corpses or even black holes ought to remain. And yet, it will still exist. Someone who could measure the spacetime curvature of the Universe or somehow detect dark matter or ultra-low energy neutrinos would encounter an enormous, diffuse halo of mass that will persist for far longer than any bound structure made of normal matter.
Eventually, dependent on the actual (and yet unknown) masses of individual dark matter particles and neutrinos, this remnant dark halo will decay, ejecting itself particle-by-particle until none remain. Until the masses and properties of those particles are known, however, we cannot calculate that timescale; we can only know it will persist longer than any normal matter will. The eventual fate of the last galaxies in the Universe will be a skeletal dark matter/neutrino halo, far outlasting anything else we’ve ever observed.”
Most of the galaxies we find in the Universe aren’t found in isolation, but exist bound to other galaxies, whether in a small group like our own or in an enormous grouping like the galaxies of the Virgo cluster. But out there, hundreds of millions of light-years away, galaxy MCG+01-02-015 exists in true isolation, with no other galaxies surrounding it for some 100 million light-years in all directions. Whereas we have tens of thousands of galaxies within that distance of ourselves, it has not even one. As a result, it’s a much cleaner astronomical laboratory, and we can predict its future far more certainly than we can predict our own.
So what is the ultimate fate of this galaxy: the loneliest one in the Universe? Come find out, with implications for everything else we know of, too!
Controversial ‘Dark Matter Free Galaxy’ Passes Its Most Difficult Test
“In theory, all galaxies should contain copious amounts of dark matter, with one exception. Galactic mergers, interactions, or gas stripping events can isolate large amounts of normal matter. These liberated clumps should gravitate and recollapse, creating dark matter-free galaxies. Detractors argued their absence proved dark matter’s non-existence. However, 2018 and 2019 saw scientists announce two dark matter-free galaxies: NGC 1052-DF2 and NGC 1052-DF4.”
One of the most counterintuitive predictions of dark matter is that, owing to the differing forces that normal matter and dark matter experience in environments rich in matter and radiation, it should be separable from normal matter. Therefore, when major galaxy mergers or interactions occur, it should be possible to strip normal matter out of the dark matter halos they’re bound to, creating dark matter-free galaxies.
Long predicted by theory but never discovered, they were used by dark matter detractors to demonstrate the insufficiency of dark matter. But in 2018, the galaxy NGC 1052-DF2 was measured well enough to conclude it was devoid of dark matter; in 2019, it was joined by NGC 1052-DF4. While a different team claimed these galaxies were closer and therefore not dark matter-free, the original researchers turned to Hubble to settle the matter.
NGC 1052-DF4 has now been measured better than ever before, and it’s at the original (farther) distance, implying that it really is dark matter-free. Come get the full story today.
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.