Merging Neutron Stars Made An Unstoppable Jet, And It Moves At Nearly The Speed Of Light
“How can you make a jet like this? We’ve only ever seen them from one other source: from black holes that are feeding on matter. That must be the clue that solves the puzzle! It isn’t that the merger itself created a jet, but that the completed merger produced a black hole, and this spinning black hole accelerated the matter around it, producing the jets that we saw afterwards. It explains why there was a dimming followed by a second round of brightening, and it explains the collimated structure and the fantastically large energies and speeds. Without a central black hole, there’s no known way to do it.
In science, sometimes the best results are the ones you weren’t expecting. We may have anticipated that merging neutron stars would create the heaviest elements of all, but no one saw a structured jet emerging from a black hole afterwards as something that should occur. Yet here we are, reaping the gifts of the Universe. It’s a reminder from the cosmos to us: the day we stop our scientific inquiries, we stop uncovering the mysteries that underlie our existence.”
On 2017, we saw two neutron stars inspiral and merge together, marking the first time we saw such a thing happen in both gravitational waves and in traditional light signals. But then we kept looking, and noticed something funny: while the light faded away after the explosion, it all of a sudden spiked again in the X-ray and radio parts of the spectrum. It took combining 207 days of data from 32 telescopes across five continents to figure out why, but the culprit is now clear.
There’s a black hole that formed, and it’s powering a jet that all the matter thrown off during the merger cannot stop. Come get the full story today.
What Was It Like When The First Stars Died?
“It’s theorized that this is the origin of the seeds of the supermassive black holes that occupy the centers of galaxies today: the deaths of the most massive stars, which create black holes hundreds or thousands of times the mass of the Sun. Over time, mergers and gravitational growth will lead to the most massive black holes known in the Universe, black holes that are millions or even billions of times the mass of the Sun by today.
It took perhaps 100 million years to form the very first stars in the Universe, but just another million or two after that for the most massive among them to die, creating black holes and spreading heavy, processed elements into the interstellar medium. As time goes on, the Universe, at long last, will begin to resemble what we actually see today.”
Our Universe, shortly after the Big Bang, proceeded in a number of momentous steps. The first atomic nuclei formed just minutes after the Big Bang, while neutral atoms took hundreds of thousands of years. It took another 50 to 100 million years for the very first star to be created, but only, perhaps, a million or two years for the most massive among the first stars to die. They may have been short-lived, but the first stars were truly spectacular, and their deaths set up the first steps in a changing Universe that would take us from a pristine set of materials to, eventually, the Universe as we know it today.
Take a major step in the cosmic journey of how we got to today by looking at what it was like when the first stars died!
What Happens When Planets, Stars, And Black Holes Collide?
“Brown dwarf collisions. Want to make a star, but you didn’t accumulate enough mass to get there when the gas cloud that created you first collapsed? There’s a second chance available to you! Brown dwarfs are like very massive gas giants, more than a dozen times as massive as Jupiter, that experience strong enough temperatures (about 1,000,000 K) and pressures at their centers to ignite deuterium fusion, but not hydrogen fusion. They produce their own light, they remain relatively cool, and they aren’t quite true stars. Ranging in mass from about 1% to 7.5% of the Sun’s mass, they are the failed stars of the Universe.
But if you have two in a binary system, or two in disparate systems that collide by chance, all of that can change in a flash.”
Nothing in the Universe exists in total isolation. Planets and stars all have a common origin inside of star clusters; galaxies clump and cluster together and are the homes for the smaller masses in the Universe. In an environment such as this, collisions between objects are all but inevitable. We think of space as being extremely sparse, but gravity is always attractive and the Universe sticks around for a long time. Eventually, collisions will occur between planets, stars, stellar remnants, and black holes.
What happens when they run into one another? Unbelievably, we not only know, we have the evidence to back it up!
6 Facts You Never Imagined About The Nearest Stars To Earth
“4.) There are no neutron stars or black holes within 10 parsecs. And, to be honest, you have to go out way further than 10 parsecs to find either of these! In 2007, scientists discovered the X-ray object 1RXS J141256.0+792204, nicknamed “Calvera,” and identified it as a neutron star. This object is a magnificent 617 light years away, making it the closest neutron star known. To arrive at the closest known black hole, you have to go all the way out to V616 Monocerotis, which is over 3,000 light years away. Of all the 316 star systems identified within 10 parsecs, we can definitively state that there are none of them with black hole or neutron star companions. At least where we are in the galaxy, these objects are rare.”
In the mid-1990s, astronomy was a very different place. We had not yet discovered brown dwarfs; exoplanet science was in its infancy; and we had discovered 191 star systems within 10 parsecs (32.6 light years) of Earth. Of course, low-mass stars have been discovered in great abundance now, exoplanet science has thousands of identified planets, and owing to projects like the RECONS collaboration, we’ve now discovered a total of 316 star systems within 10 parsecs of Earth. This has huge implications for what the Universe is actually made of, which we can learn just by looking in our own backyard. From how common faint stars are to planets, lifetimes, multi-star systems and more, there’s a huge amount of information to be gained, and the RECONS collaboration just put out their latest, most comprehensive results ever.
We’ve now confidently identified over 90% of the stars that are closest to us, and here’s what we’ve learned so far. Come get some incredible facts today!
LIGO’s Greatest Discovery Almost Didn’t Happen
“If all we had done was look at the automated signals, we would have gotten just one “single-detector alert,” in the Hanford detector, while the other two detectors would have registered no event. We would have thrown it away, all because the orientation was such that there was no significant signal in Virgo, and a glitch caused the Livingston signal to be vetoed. If we left the signal-finding solely to algorithms and theoretical decisions, a 1-in-10,000 coincidence would have stopped us from finding this first-of-its-kind event. But we had scientists on the job: real, live, human scientists, and now we’ve confidently seen a multi-messenger signal, in gravitational waves and electromagnetic light, for the very first time.”
Imagine the scene: it’s mid-August, 2017, and the Virgo detector has just joined the twin LIGO detectors barely two weeks ago. Amazingly, on August 14th, you’ve seen a gravitational wave signal in all three detectors; another black hole-black hole merger. Then, all of a sudden, even though the LIGO detectors are set to shut down later in the month, an extraordinarily significant signal goes off… but only in one detector. The LIGO Hanford detector sees a signal with a false-alarm probability of just one part in 300 billion; a slam dunk. Yet both LIGO Livingston and Virgo see nothing. A non-coincident signal should automatically be rejected, but somehow, one of the young researchers working on the project thought to check the Livingston data by hand… and that was where the secret lay.
LIGO’s greatest discovery, of two merging neutron stars, almost was overlooked. Thankfully, the hands-on nature of the scientists working on gravitational waves were able to turn this into the discovery of the century! (So far!)
Ask Ethan: How Does Spinning Affect The Shape Of Pulsars?
“[S]ome pulsars have incredible spin rates. How much does this distort the object, and does it shed material this way or is gravity still able to bind all of the material to the object?”
If you spin too quickly, the matter on the outskirts of your surface will fly off. If you’re in hydrostatic equilibrium, your shape will simply distort until your equatorial bulge and your polar flattening result in the most stable, lowest-energy configuration. For our Earth, this means the best place to launch a rocket is near the equator, and our planet’s polar diameter is a little more than 20 km shorter than its equatorial diameter. But what about for the fastest-rotating natural object we know of: a neutron star. While most neutron stars rotate a few times a second, the fastest one makes 766 rotations in that span, meaning that a neutron on the surface moves at about 16% the speed of light. Much faster, and could it escape? Or, perhaps, is the pulsar’s shape highly distorted, either due to that rotation or to the incredibly strong magnetic fields inside? Neutron star matter is very different from anything we’re used to, so don’t bet on any of those.
Other than the first few fractions-of-a-second, changes to neutron stars are slow and mostly inconsequential. Come find out how bad it is on this edition of Ask Ethan!
Why Neutron Stars, Not Black Holes, Show The Future Of Gravitational Wave Astronomy
“3.) Gravitational waves move at exactly the speed of light! Before this detection, we never had a gravitational wave and a light signal simultaneously identifiable to compare with one another. After a journey of 130 million light years, the first electromagnetic signal from this detection arrived just 1.7 seconds after the peak of the gravitational wave signal. That means, at most, the difference between the speed of gravity and the speed of light is about 0.12 microns-per-second, or 0.00000000000004%. It’s anticipated that these two speeds are exactly equal, and the delay of the light signal comes from the fact that the light-producing reactions in the neutron star take a second or two to reach the surface.”
Detecting black holes and the gravitational wave signals from them was an incredible feat, but doing the same thing for neutron star mergers is a true game-changer. Instead of fractions of a second, neutron star mergers show up for up to half a minute. Unlike black holes, there’s an electromagnetic counterpart. Because of that, we can verify that the speed of gravity really is identical to the speed of light: to better than 1 part in 1,000,000,000,000,000. And perhaps most spectacularly, we can bring the electromagnetic and gravitational-wave skies together for the first time. Even though LIGO has seen more merging black holes, the fact is that there are more merging neutron stars. The key, now, is finding them. We live at a moment where gravitational wave astronomy is just in its infancy, giving us a whole new way to look at the Universe.
For the first time, we’re doing it. Here’s the incredible science of what we’re actually learning, and what the future of gravitational wave + electromagnetic astronomy now holds.
Astronomy’s ‘Rosetta Stone’: Merging Neutron Stars Seen With Both Gravitational Waves And Light
“For the first time in history, gravitational wave astronomy isn’t a pipe dream, nor is it a way of looking for esoteric objects we can’t see via any other means. Instead, it’s truly a part of our night sky, and the first signpost of an astronomical cataclysm. In the future, as gravitational wave astronomy improves, it may even serve as an early warning system, enabling us to locate sources about to merge before they ever do so. It may grow to include not only black holes and neutron stars, but white dwarfs and supermassive black holes swallowing objects as well. Gravitational wave astronomy is only two years old, and we haven’t even taken it to space yet. The next step in understanding the Universe is before us. Sit back and enjoy the ride!”
When the Advanced LIGO detectors turned on in 2015, it shook up the world when they detected their first event: the merger of two quite massive black holes. Since that time, they’ve observed black hole-black hole mergers multiple times, with the VIRGO detector in Italy joining them for the fourth event. But this wasn’t what LIGO/VIRGO expected to see; rather, they were built to hunt for merging neutron stars that were much closer by. Neutron star mergers would be superior to black hole mergers in an extraordinary way: it would enable other astronomers to get in on the action. Unlike black holes, merging neutron stars should emit radiation across the electromagnetic spectrum, from gamma-rays to UV/optical afterglows. On August 17th, LIGO and VIRGO saw their very first neutron star merger, pinpointing its location to galaxy NGC 4993, just 120 million light years away.
For the first time, we’ve joined the gravitational wave and light-based skies together with an incredible event. It’s a glorious step forward. And it’s just the beginning.
The Scientific Story Of How Each Element Was Made
“Neutron star mergers create the greatest heavy element abundances of all, including gold, mercury, and platinum.
Meanwhile, cosmic rays blast nuclei apart, creating the Universe’s lithium, beryllium, and boron.
Finally, the heaviest, unstable elements are made in terrestrial laboratories.
The result is the rich, diverse Universe we inhabit today.”
When the Big Bang first occurred, the Universe was filled with all the various particles and antiparticles making up the Standard Model, and perhaps still others yet to be discovered. But missing from the list were protons, neutrons, or any of the atomic nuclei key to the life-giving elements in our Universe today. Yet the Universe expanded, cooled, antimatter annihilated away, and the first elements began to take shape. After billions of years of cosmic evolution, we arrived at a Universe recognizable today: full of stars, planets, and the full complement of elements populating the periodic table. More than 100 elements are known today, 91 of which are found to occur naturally on Earth. Some were formed in the Big Bang, others were formed in stars, still others were formed in violent cosmic cataclysms or collisions. Yet every one has an origin whose story is now known, giving rise to all we interact with today.
Come get the full story behind how all the elements were made in some fantastic pictures, visuals, and no more than 200 words on this edition of Mostly Mute Monday!