The exact date of Betelgeuse's explosion is anyone's guess. It may have already happened, because it takes six centuries for its light to reach us. The best estimate scientists can give us is that it will likely go supernova sometime in the next 100,000 years – a mere blink of the eye by cosmic standards.
When the fateful day arrives Betelgeuse will explode as a Type II supernova. When its outer layers are blown outward at some five percent of the speed of light, its remaining core will rapidly shrink to become a neutron star some 20 kilometers across - a solid ball of nuclear matter, so dense that a thimbleful of its contents would outweigh all the world's naval vessels.
Seen from Earth, the exploding Betelgeuse will get nearly as bright as the full Moon and be visible for two or three months in broad daylight. But, at our distance, we won't be in any danger because the vast amount of energy released by the supernova will be spread over an expanding bubble in space with a surface area of more than a million square light-years. This is where the inverse square law becomes paramount, where the intensity of the explosion is inversely proportional to the square of the distance. This means that as the distance from Betelgeuse increases, the intensity of the radiation and shock given off by the supernova explosion is equal to a value multiplied by 1/d2, where d = distance.
Type II supernovae don't pose any threat to planets that are hundreds of light-years away because their initially deadly radiation spreads out equally in all directions and eventually becomes too thin to be of concern. The explosion is simply dissipated by the interstellar medium long before it reaches Earth.
as a lay person i didnt know how the radiation from such an explosion might affect us here i have heard that a gama ray burst from a quasar would be bad for any one in the path but thats a different ball of string (theory?) thanks for the info and if you know about gama ray burst i would love to know it that is true
First off, you must understand what quasars are. The term quasar derives from how these objects were originally discovered in the earliest radio surveys of the sky in the 1950s. Some radio sources, however, coincided with objects that appeared to be unusually blue stars, although photographs of a percentage of these objects showed them to be embedded in faint, fuzzy halos. Because of their almost starlike appearance, they were dubbed “quasi-stellar radio sources,” which by 1964 had been shortened to “quasar.”
Continuing observations of quasars revealed that their brightness can vary significantly on timescales as short as a few days, meaning that the total size of the quasar cannot be more than a few light-days across. Since the quasar is so compact and so luminous, the radiation pressure inside the quasar must be huge; indeed, the only way a quasar can keep from blowing itself up with its own radiation is because it is very massive, at least a million solar masses if it is not to exceed the Eddington limit—the minimum mass at which the outward radiation pressure is balanced by the inward pull of gravity (named after English astronomer ). Astronomers were faced with a conundrum: how could an object about the size of the solar system have a mass of about a million stars and outshine by 100 times a galaxy of a hundred billion stars?
By 1965 it was recognized that quasars are part of a much larger population and most of these are much weaker radio sources too faint to have been detected in the early radio surveys. This larger population, sharing all quasar properties except extreme radio luminosity, became known as “quasi-stellar objects” or simply QSOs. Since the early 1980s most astronomers have regarded QSOs as the high-luminosity variety of an even larger population of “active galactic nuclei” or AGNs. (The lower-luminosity AGNs are known as “Seyfert galaxies,” named after the American astronomer Carl K. Seyfert, who first identified them in 1943.)
As a result, it can be seen that quasars, viewed as distant star like objects which may vary slightly in luminosity over time, are not prone to the type of sudden bursts we associate with explosive supernova ejecta or a gamma ray burst.
First discovered in the 1960s by U.S. military satellites looking for covert nuclear tests, and when first discovered they nearly triggered a USAF airborne alert, gamma-ray bursts are short-lived explosions of gamma rays, the most energetic form of light. Lasting from a few milliseconds to several hours, they shine hundreds of times brighter than a typical supernova and about a million trillion times as bright as the Sun. Observed in distant galaxies, they are the brightest electromagnetic events known to exist in the universe. A typical burst releases as much energy in a few seconds as the Sun will in its entire 10 billion year lifetime.
Gamma-ray bursts do not come from any particular direction in space, though they are associated with very faint galaxies at enormous distances. The explosions are thought to be highly focused, with most of the energy collimated into a narrow jet traveling near the speed of light. We can only detect the jets of gamma-ray bursts pointed directly at us.
Imagine, if you will, a light house with the two collimated beams. Each beam, as it sweeps across the horizon could equate to a beam of high energy gamma rays. We only see it when it flashes.
Astronomers classify gamma-ray bursts into long- and short-duration events. While the two types of events are likely created by different processes, both result in the creation of a new black hole. Long-duration bursts last anywhere from 2 seconds to several hours. Although they are associated with the deaths of massive stars in supernovas, not every supernova results in a gamma-ray burst. Short-duration bursts last less than 2 seconds. They appear to result from the merger two neutron stars into a new black hole, or the merger of a neutron star and a black hole to form a larger black hole.
In 2017, NASA’s Fermi telescope observed that a short-duration gamma-ray burst was tied to the gravitational waves detected by the National Science Foundation’s Laser Interferometer Gravitational-Wave Observatory (LIGO). A pair of colliding neutron stars was thought to have created an immensely explosive kilonova, (a kilonova, also called a macronova or r-process supernova, is a transient astronomical event that occurs in a compact binary system when two neutron stars or a neutron star and a black hole merge or collide into each other) along with the gamma-ray burst and the gravitational waves. Hubble set out to observe the kilonova and capture its near-infrared spectrum, which revealed the motion and chemical composition of the expanding debris. The spectrum looked exactly how theoretical physicists had predicted the outcome of the merging of two neutron stars would appear.
In essence, quasars are long term events associated active galactic nuclei, while gamma ray bursts are tied to the collision or merging of neutron stars together or with a black hole and has a short lived explosive appearance. (See Britannica and Hubblesite.org for vastly more information on both items)
More than the mainstream physics community thinks.
The Crab Nebula Pulsar Supernova is misclassified. It is currently thought to be an Electron Capture supernova. It's not. It is a matter-anti-matter pair instability supernova, which is about 100 times as energetic as Electron Capture. Now the proof is in the pudding, and whenever Betelgeuse finally explodes I'll eat crow if I'm wrong, from the grave of all places .
Betelgeuse is slightly more massive than the Crab Nebula Progenitor star would need to be, but should produce the same basic type of supernova when it collapses. This allows me to calculate what the effects of the Supernova would be on the Earth, which I have done several years ago after studying the Crab Nebula Pulsar.
According to my past calculations, a Betelgeuse Supernova will produce about 0.19watts/m^2 flux on the Earth for about 2 years. This is the average, however depending on the shape of the explosion the real value may spike significantly higher than this at times. The current forcing due to man-made Carbon Dioxide on Earth's climate is 0.5Watts/m^2 (Vs Pre-industrial levels of CO2 anyway). So you can see Betelgeuse supernova would accelerate Global Warming by about 40% for about 2 years...
Fortunately, the polar jet of Betelgeuse will NOT hit the Earth when it explodes, because Betelgeuse poles are not oriented towards the Earth system, so there is no threat of a Gamma Ray Burst destroying the Earth's atmosphere, Betelgeuse is too far away for the radial blast to significantly damage the Earth over human time scales, though in some far distant future some of the meteors produced during the Supernova might eventually make it all the way to our part of the galaxy, they will be moving so fast, above galactic escape velocity, that they would be unlikely to hit the Earth or any of the other planets in our system.