New LIGO Events Demolish The Idea Of A ‘Mass Gap’ Between Neutron Stars And Black Holes
“For decades, we knew only of neutron stars that existed below about twice the Sun’s mass, and black holes that existed at or above about five times the Sun’s mass. Beginning in 2017, we started to see neutron stars merging together to form black holes that fell into that empty range, but those events were relatively infrequent. However, this latest discovery — of two low-mass black holes merging together to form a heavier black hole — should close off the “mass gap” range for good.
What was once a region of unknowns should now be filled in by black holes. Although there’s still a lot of science left to do to determine how rare or common black holes of different masses are, particularly in the realm of population statistics, it would now be very surprising if there were a gap in masses between neutron stars and black holes. LIGO’s latest data has demolished that idea. Despite cries of, “NOT NOW LIGO,” the Universe continues to send data our way, and our scientific discoveries go on.”
For decades, we’ve known that supernovae make both neutron stars and black holes. But until LIGO started detecting gravitational waves, we’d never seen a neutron star over 2 solar masses, and we’d never seen a black hole of less than 5 solar masses. Although LIGO saw two neutron stars merge to form a black hole a couple of times, leading to a black hole in that “mass gap” range in both instances, it had never seen two “mass gap” black holes merging before.
Well, we’re almost a year into LIGO’s third (and upgraded) data run, and already it’s seen four, including a new one this past Monday. The mass gap should be gone, and LIGO’s the observatory that demolished it.
Ask Ethan: Could Gravitational Waves Ever Cause Damage On Earth?
“The gravitational waves detected on Earth by LIGO traveled great distances and were quite weak per unit volume of space by the time they arrived. If they originated much closer to Earth, they would be more energetic from our perspective. What would the effect of energetic gravitational waves created locally be on nearby objects. I’m thinking of binary ~30 solar mass black holes merging. Would the gravitational waves be noticeable? Could they cause damage?”
The first black hole-black hole merger we ever observed occurred some 1.3 billion light-years from Earth. It compressed the entire planet, at maximum amplitude, by about the width of a dozen protons, imparting just a tiny amount of energy (about 0.7 seconds worth of sunlight shining on Manhattan island) to the entire Earth in the process. But we were able to leverage that tiny effect to great effect with gravitational wave detectors such as LIGO, where we now have approximately 50 candidate detections under our collective belts. If these black holes were just 1 light-year away instead of 1.3 billion, they’d strike Earth with more energy than the Sun produces over about 3 minutes.
And yet, the damage would be absolutely negligible, unless two black holes were to merge somewhere within our own Solar System. Here’s the full story.
What The 3 Biggest Physics Discoveries Of The Decade Mean For The Future Of Science
“As the coming decades unfold, we won’t simply measure how one or two supermassive black holes in the Universe evolve, but dozens or even hundreds. It’s possible that stellar-mass black holes will enter the fold as well, as they’re contained within our own galaxy and thus appear relatively large. It’s even possible that we’ll get a surprise, and the black holes that appear to be quiet will exhibit radio signatures that these telescope arrays can pick up, after all.
There is a clear path laid out to continued exploration of the Universe, and all it relies on is extending what we’re already doing. We do not know what secrets nature holds beyond the already explored frontiers, but we do know one thing for certain: if we don’t look, we’ll never learn.”
The 2010s saw an enormous array of scientific achievements, from an explosion of exoplanet discoveries to quantum supremacy to laser advances to cosmological measurements, visiting Pluto, entering interstellar space and more. But three discoveries not only shook up the world, but have profound implications for the future of science in the 21st century.
The Higgs boson, gravitational waves, and measuring an event horizon are the big 3 physics discoveries of the 2010s. Here’s what they mean for our future.
Advanced LIGO Just Got More Advanced Thanks To An All-New Quantum Enhancement
“The current observing run of LIGO has been going on since April of this year, and there are already more than double the number of candidate signals than the total number of signals from all previous runs combined. This isn’t due to using the same instruments for longer periods of time, but owes this newfound success to some very exciting upgrades, including this clever new technique of squeezed quantum states.
For decades, scientists have had the idea to leverage squeezed quantum states to reduce the quantum uncertainty in the most important quantities for gravitational wave detections. Thanks to hard work and remarkable advances made by the LIGO Scientific Collaboration, this new, third observing run is already seeing more success than any gravitational wave detector in history. By reducing the phase uncertainty in the quantum vacuum that LIGO’s photons experience, we’re in exactly the right position to make the next great breakthrough in astrophysics.”
Did you know that LIGO and Virgo have been engaged in a new observing run since April of this year? Have you heard that the new run is up to 50% more sensitive than prior runs? That’s true, and it’s due to a number of improvements in noise reduction, including one fascinating way to leverage and control how quantum uncertainty plays out. These squeezed quantum states enable you to put the uncertainty where you most want it, and measure the corresponding quantity even more precisely as a result.
Come find out how we’re bending the quantum rules of the Universe to our will for the benefit of science; it’s a remarkable story!
This Is Why ‘Multi-Messenger Astronomy’ Is The Future Of Astrophysics
“The three types of signals we know how to collect from the Universe — light, particles, and gravitational waves — all deliver fundamentally different types of information right to our front door. By combining the most precise observations we can take with each of these, we can learn more about our cosmic history than any one of these signal types, or “messengers,” can provide in isolation.
We’ve already learned how neutrinos are produced in supernova, and how their travel path is less impeded by matter than light’s is. We’ve already linked merging neutron stars with kilonovae and the production of the heaviest elements in the Universe. With multi-messenger astronomy still in its infancy, we can expect a deluge of new events and new discoveries as this science progresses throughout the 21st century.
Just as you can learn more about a tiger by hearing its growl, smelling its scent, and watching it hunt than you can from a still image alone, you can learn more about the Universe by detecting these fundamentally different types of messengers all at once. Our bodies might be limited in terms of the senses we can use in any given scenario, but our knowledge of the Universe is limited only by the fundamental physics governing it. In the quest to learn it all, we owe it to humanity to use every resource we can muster.”
In 2017, three different gravitational wave observatories from across the world, LIGO Livingston, LIGO Hanford, and the Virgo detector all witnessed the arrival of gravitational waves from a neutron star collision some 130,000,000 light-years away. Two seconds after the wave signal ceased, the first light from the merger arrived. A new term that was previously reserved for professional astronomers, “multi-messenger astronomy,” suddenly entered the public arena.
But what is multi-messenger astronomy? What makes something a “messenger” and why is it important? As it turns out, it’s going to revolutionize how we understand our Universe in the 21st century. Come find out how today.
LIGO’s Lasers Can See Gravitational Waves, Even Though The Waves Stretch The Light Itself
“But this is where the puzzle comes in: if space itself is what’s expanding or compressing, then shouldn’t the light moving through the detectors be expanding or compressing too? And if that’s the case, shouldn’t the light travel the same number of wavelengths through the detector as it would have if the gravitational wave had never existed?
This seems like a real problem. Light is a wave, and what defines any individual photon is its frequency, which in turn defines both its wavelength (in a vacuum) and its energy. Light redshifts or blueshifts as the space it’s occupying stretches (for red) or contracts (for blue), but once the wave has finished passing through, the light returns to the same wavelength it was back when space was restored to its original state.
It seems as though light should produce the same interference pattern, regardless of gravitational waves.”
Have you ever thought about how gravitational wave detectors work? By passing light down two mutually perpendicular arms, reflecting them back and reconstructing an interference pattern, we can detect a passing wave by how it changes the arm-lengths of the light. But the light itself also gets compressed and expanded, and shouldn’t those effects cancel out?
Clearly, LIGO, Virgo and KAGRA all work, as many detected events bear out. But have you ever thought about how? Come get the answer today!
Can We Test Gravitational Waves For Wave-Particle Duality?
“Although we have every reason to believe that gravitational waves are simply the quantum analog of electromagnetic waves, we have, unlike the electromagnetic photon, not yet risen to the technological challenges of directly detecting the gravitational particle that’s the counterpart of gravitational waves: the graviton.
Theorists are still calculating the uniquely quantum effects that should arise and are working together with experimentalists to design tabletop tests of quantum gravity, all while gravitational wave astronomers puzzle over how a future-generation detector might some day reveal the quantum nature of these waves. Although we expect gravitational waves to exhibit wave-particle duality, until we detect it, we cannot know for certain. Here’s hoping that our curiosity compels us to invest in it, that nature cooperates, and that we find out the answer once and for all!”
One of the revolutionary discoveries of the quantum world was that every particle that we know of also behaves as a wave. Photons are the quanta associated with light, and every light wave is made up of a discrete number of photons. Particles like electrons also can behave as waves; if you send them through a double slit, even one-at-a-time, they’ll produce an interference pattern.
So what about gravitational waves? We’ve seen the wave part; could we ever test them for the “particle” part of that? Find out today!
Has LIGO Just Detected The ‘Trifecta’ Signal That All Astronomers Have Been Hoping For?
“Of course, all of this is just preliminary at this point. The LIGO collaboration has yet to announce a definitive detection of any type, and the IceCube event may turn out to be either a foreground, unrelated neutrino or a spurious event entirely. No electromagnetic signal has been announced, and there might not be one at all. Science moves slowly and carefully, as it should, and all of what’s been written here is a best-case scenario for the optimistic hopefuls out there, not a slam-dunk by any means.
But if we keep watching the sky in these three fundamentally different ways, and keep increasing and improving the precision at which we do so, it’s only a matter of time before the right natural event gives us the signal every astronomer has been waiting for. Just a generation ago, multi-messenger astronomy was nothing but a dream. Today, it’s not just the future of astronomy, but the present as well. There’s no moment in science quite as exciting as being on the cusp of an unprecedented breakthrough.”
There haven’t been any official releases, announcements, or claimed discoveries, but many of you may be aware that back in April, LIGO turned on again and began searching the Universe for gravitational waves, this time with improved range and sensitivity. Over that time, some 24 candidate events have been seen, and the most recent one, from July 28, 2019, is perhaps something special. Located 2.9 billion light years away and likely to be a black hole-black hole merger, it just happens to coincide with the arrival of a cosmic neutrino, in both space and time, as seen by IceCube.
Electromagnetic follow-ups are currently underway, and this could mark the first threefold multi-messenger astronomy signal ever! Watch this one closely, as it could herald a new dawn for astronomy in human history!
Ask Ethan: Why Do Gravitational Waves Travel Exactly At The Speed Of Light?
We know that the speed of electromagnetic radiation can be derived from Maxwell’s equation[s] in a vacuum. What equations (similar to Maxwell’s – perhaps?) offer a mathematical proof that Gravity Waves must travel [at the] speed of light?
If you were to somehow make the Sun disappear, you would still see its emitted light for 8 minutes and 20 seconds: the amount of time it takes light to travel from the Sun to the Earth across 150,000,000 km of space. But what about gravitation? Would the Earth continue to orbit where the Sun was for that same 8 minutes and 20 seconds, or would it fly off in a straight line immediately?
There are two ways to look at this puzzle: theoretically and experimentally/observationally. From a theoretical point of view, this represents one of the most profound differences from Newton’s gravitation to Einstein’s, and demonstrates what a revolutionary leap General Relativity was. Observationally, we only had indirect measurements until 2017, where we determined the speed of gravity and the speed of light were equal to 15 significant digits!
Gravitational waves do travel at the speed of light, which equals the speed of gravity to a better precision than ever. Here’s how we know.
Ask Ethan: Why Haven’t We Found Gravitational Waves In Our Own Galaxy?
“Why are all the known gravitational wave sources (coalescing binaries) in the distant universe? Why none has been detected in our neighborhood? […] My guess (which is most probably wrong) is that the detectors need to be precisely aligned for any detection. Hence all the detection until now are serendipitous.”
On September 14, 2015, our view of the Universe changed forever with the first direct detection of gravitational waves. Since then, we’ve detected a variety of black hole and neutron star binaries in the final, end-stages of coalescence, culminating in a spectacular merger. But they’re all hundreds of millions or even billions of light-years away!
Simultaneously, we know that we have neutron stars and black holes in binary systems here in our own galaxy. But of all the gravitational waves that LIGO and Virgo have detected, none of these objects are among them. This remains true, even though we can identify many of them from their electromagnetic signatures.
Why haven’t we found gravitational waves in our own galaxy? Give us a better observatory and we will! Here’s the full scientific story on that.