Black Holes and Gravitational Waves:The Warp and Woof of Spacetime

#GravitationalWaves #LIGO #NeutronStars #EinsteinTheory #CosmicDiscovery #Astronomy #Physics #Kilonova #SpaceExploration #AstronomyLovers What you’re about to watch is an exciting adventure into the realm of gravitational waves, a discovery that has opened a new window into the universe. Welcome, and let’s dive into the incredible journey that began with the first detection of gravitational waves in 2016 and has continued to shape our understanding of the cosmos. In our last lecture, we talked about how gravitational waves were discovered as a culmination of over four to five decades of work, with the LIGO observatories playing a key role. The initial detection earned the Nobel Prize for the scientists who contributed to this groundbreaking discovery. Since then, there have been six additional confirmed sightings of gravitational waves, each offering new insights into cosmic events. I’ll lead you through the most recent and most significant of these detections. Gravitational waves, predicted by Einstein’s general relativity, can be detected by terrestrial interferometers like LIGO. These waves are generated by extremely energetic events, such as rotating neutron stars with “starquakes,” supernovae, and, most notably, collisions of compact objects like black holes and neutron stars. For instance, neutron stars are incredibly dense remnants of supernova explosions. These stars are typically between one and three times the mass of our sun but compressed into a sphere only a few kilometers in diameter. Because of their density and strong magnetic fields, neutron stars can emit beams of electromagnetic radiation as pulsars. The story of gravitational wave detection began way back in 1974, when Russell Hulse and Joseph Taylor discovered the first binary pulsar, which earned them the Nobel Prize in 1993. They observed variations in the pulses from the binary, proving that the system was losing energy through gravitational waves, as predicted by Einstein. But what happens when two neutron stars collide? This is what we’ll explore next. I’ll show you how such collisions produce not only gravitational waves but also gamma ray bursts—brief and intense flashes of gamma radiation. In August 2017, a groundbreaking discovery was made when the LIGO and Virgo observatories detected gravitational waves from a neutron star collision. Just seconds later, gamma ray bursts were observed by the Fermi and INTEGRAL space telescopes, marking the first joint detection of gravitational waves and electromagnetic radiation. This event, known as GW170817, triggered a worldwide effort to locate and study the source. Within hours, astronomers identified the host galaxy, NGC 4993, located about 130 million light-years away. This was the first time anyone had observed light from a gravitational wave source, providing invaluable data. When neutron stars merge, they create a phenomenon known as a kilonova, which is about a thousand times brighter than a typical supernova. The kilonova from GW170817 was studied across the electromagnetic spectrum—from X-rays and visible light to infrared and radio waves—giving us a complete picture of the event. I will guide you through the details of this kilonova. As the neutron stars collided, they released a tremendous amount of energy. Observations revealed that these mergers produce heavy elements like gold and platinum. In fact, it’s estimated that about ten Earth masses of gold and platinum were formed in this single event. The implications of this discovery are profound. Not only do neutron star mergers explain the origin of many heavy elements in the universe, but they also provide a new way to study extreme physics. The data from GW170817 matched predictions from Einstein’s theory of relativity, further validating our understanding of gravitational waves. The future of astronomy will undoubtedly include more gravitational wave detections. As LIGO and Virgo continue to upgrade and improve, we can expect to observe more mergers, uncovering even more secrets of the universe. Join me as we delve into this groundbreaking discovery and explore the endless possibilities it opens for studying the cosmos. This is part of my complete intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter. 0:00 Introduction 1:00 September 14, 2015 - 1.3 billion years... 4:47 The Sound of Two Black Holes Colliding 6:10 2017 Nobel Prize in Physics 15:03 Nearly flat spacetime with a little bump 21:30 So how do things move as the wave passes by? 23:24 BUT, they do change distance! 26:15 Gravitational Wave Observatories 28:25 Wave Patterns of Gravitational Waves 34:08 The Most Precise Ruler Ever Constructed 36:46 Zooming into an Atom 38:12 Gravitational-Wave Observatories 48:29 Timing and Profile of the Signals 53:19 Spiraling Black Holes 55:05 Warped Spacetime Around Colliding Black Holes 59:53 Exaggerated Effects of Gravitational Waves