Gamma Ray Bursts: Unveiling the Universe’s Most Powerful Explosions

#GammaRayBursts #Supernovae #BlackHoles #AstronomyLecture #CosmicExplosions #Astrophysics #HubbleSpaceTelescope #NeutronStarCollisions #Hypernova #StellarEvolution

This is part of my Intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter.

What you’re about to watch is an exciting deep dive into the spectacular results of some of the most massive stellar explosions in the universe—events that create black holes. This time, we’re focusing on supermassive stars, much larger than 15 or 20 times the mass of our sun, which can explode as type one supernovae and collapse into black holes. I’ll lead you through the fascinating history of how we discovered these phenomena by studying gamma ray bursts, the final signals of black hole formation. Let’s get started by understanding why gamma ray bursts caught our attention in the first place. Gamma rays are the highest energy form of light, with the shortest wavelengths. So why did we start looking for gamma ray bursts? It all began in the 1960s during the Cold War when the United States and the Soviet Union were conducting nuclear tests which generated gamma rays. To monitor these tests, the United States launched the Vela satellites, designed to detect gamma rays from nuclear bombs. These satellites inadvertently detected gamma ray bursts that didn’t match nuclear bomb signatures. Over time, scientists realized these bursts were not coming from Earth but from outer space. I’ll show you how this realization led to a new field of gamma ray astronomy when the data was declassified and published in 1973. Initially, gamma ray astronomy didn’t advance much until the launch of the Compton Gamma Ray Observatory in 1991, carrying the Burst and Transient Source Experiment (BATSE). This instrument observed thousands of gamma ray bursts and revealed that they were isotropic—spread uniformly across the sky, indicating cosmic distances. In 1997, the BeppoSAX satellite provided a breakthrough by detecting the first afterglow of a gamma ray burst in X-rays, followed by a visible light counterpart found with ground-based telescopes. This confirmed that gamma ray bursts were coming from distant galaxies, billions of light years away. In 2004, the Swift Gamma Ray Burst Mission was launched, revolutionizing the study of gamma ray bursts. Swift could rapidly change its orientation to capture afterglows in multiple wavelengths, providing precise locations for follow-up studies. This satellite has observed over a thousand gamma ray bursts, confirming their cosmic origins. We’ll explore remarkable events like the April 27, 2013, gamma ray burst detected by the Fermi Gamma-ray Space Telescope, which was the most energetic ever recorded. This burst was visible to the naked eye, a testament to its incredible brightness and energy. I’ll guide you through the prevailing theories on these bursts. The leading explanation involves hypernovae—a type of supermassive star explosion that creates a black hole. This process involves a collapsing star forming an accretion disk and a jet, which punctures through the star, emitting gamma rays. I’ll show you how observations confirm these theories. For example, Hubble Space Telescope images reveal hypernovae and their afterglows, linking long-duration gamma ray bursts to star-forming regions in distant galaxies. These findings underscore the cataclysmic events that generate gamma ray bursts and contribute to black hole formation. Finally, we’ll discuss neutron star collisions, another source of gamma ray bursts. In 2017, the collision of two neutron stars provided direct evidence for this phenomenon, confirming the theoretical models. Join me as we delve into the physics behind gamma ray bursts, supernovae, and the formation of black holes, revealing the dramatic events that shape our universe.

Here are some WOOPS items:
1) At about 35:10, the screen blanks out.

Swift Gamma-Ray Burst Mission: https://swift.gsfc.nasa.gov/about_swift/
2704 Gamma-Ray Bursts: https://gammaray.nsstc.nasa.gov/batse...
NASA's Swift Spots its Thousandth Gamma-ray Burst: https://www.nasa.gov/feature/goddard/...
BATSE Gamma Ray Burst Light Curves: https://gammaray.nsstc.nasa.gov/batse...
Breakthrough Study Confirms Cause of Short Gamma-Ray Bursts: https://www.nasa.gov/topics/universe/...
"ROSETTA STONE" FOUND TO DECODE THE MYSTERY OF GAMMA RAY BURSTS: https://www.nasa.gov/centers/goddard/...
The Gamma-ray Sky: https://svs.gsfc.nasa.gov/11545
SMOKE AND MIRRORS: SIGNAL-TO-NOISE AND TIME-REVERSED STRUCTURES IN GAMMA-RAY BURST PULSE LIGHT CURVES, Jon Hakkila: https://arxiv.org/pdf/1804.10130.pdf
Discovered! Neutron star collision seen for the first time: https://www.eurekalert.org/pub_releas...
Neutron star merger animation ending with kilonova explosion: https://www.eso.org/public/videos/eso...