It's wild that if we were to see the Supernova today, that means that Betelgeuse exploded over 700 years ago and we're just seeing what happened as the light that traveled trillions of miles finally reached us.
Betelgeuse: Star's weird dimming sparks rumors that its death is imminent
by Daniel Brown, The Conversation
Betelguese is the red star in the top right quarter of the picture. Credit: Hubble European Space Agency
Every season has its characteristic star constellations in the night sky. Orion—one of the most recognizable—is distinctly visible on crisp, clear winter nights in the northern hemisphere. The constellation is easy to spot even in light-polluted cities, with its bright stars representing the shape of a person.
Betelgeuse, marking Orion's top left shoulder, is often its brightest star. Red in color, this star is usually the 12th brightest in the entire sky. But it has recently dimmed dramatically to an all time low of 21st brightest star in the sky. As a result, many have started speculating about whether it could be about to explode. But could it? And what would that look like?
Betelgeuse is what astronomers call a red supergiant, up to 20 times more massive than our sun. Red supergiant stars have neared the end of their lifetime and have substantially expanded. Betelgeuse has a radius of approximately 900 times that of our sun. If the sun was this size, its surface would nearly reach Jupiter.
Betelgeuse, which is 640 light years away, is the only star other than our own whose surface we can directly picture in detail. Luckily, that can help us understand why it varies so much in brightness. At this size, stars transport their energy or heat generated in their core to the surface via convection—a method of transport we experience when we boil eggs. As the water boils, it moves up while cold water moves down to be heated. These rising and falling currents are known as convection cells.
Orion seen in Nottingham at 10pm, January 15, 2019. Credit: Daniel Brown
Each of these cells is only a few centimeters across in this example, but in Betelgeuse they are gigantic and moving much more slowly while interacting with the star's substantial magnetic field. Since the heat of the surface of the star determines its brightness, Betelgeuse shows a rather large variation of darker and brighter patches on its surface. As the star bubbles and rotates, we will see a slowly variable brightness, as we do now.
Another interesting feature is that the surface of Betelgeuse is rather cool, hence its red color. Because it has a huge radius, it also has a diminished gravitational grip on its outer surfaces. This means it loses some of its material—creating dusty clouds in its surroundings which could cause dimming as they move in front of the star.
You can monitor Betelgeuse's change in brightness yourself using only your eyes and no telescopes at all. In the northern hemisphere, Orion is observable during the first half of the night well into February. Compare Betelgeuse to other stars of different brightness to determine how bright it is. Pollux in Gemini is currently of similar brightness and Bellatrix in Orion is a bit fainter. The image below gives several other stars in and around Orion that can be used for comparison.
Betelgeuse: Star's weird dimming sparks rumors that its death is imminent
by Daniel Brown, The Conversation
Betelguese is the red star in the top right quarter of the picture. Credit: Hubble European Space Agency
Every season has its characteristic star constellations in the night sky. Orion—one of the most recognizable—is distinctly visible on crisp, clear winter nights in the northern hemisphere. The constellation is easy to spot even in light-polluted cities, with its bright stars representing the shape of a person.
Betelgeuse, marking Orion's top left shoulder, is often its brightest star. Red in color, this star is usually the 12th brightest in the entire sky. But it has recently dimmed dramatically to an all time low of 21st brightest star in the sky. As a result, many have started speculating about whether it could be about to explode. But could it? And what would that look like?
Betelgeuse is what astronomers call a red supergiant, up to 20 times more massive than our sun. Red supergiant stars have neared the end of their lifetime and have substantially expanded. Betelgeuse has a radius of approximately 900 times that of our sun. If the sun was this size, its surface would nearly reach Jupiter.
Betelgeuse, which is 640 light years away, is the only star other than our own whose surface we can directly picture in detail. Luckily, that can help us understand why it varies so much in brightness. At this size, stars transport their energy or heat generated in their core to the surface via convection—a method of transport we experience when we boil eggs. As the water boils, it moves up while cold water moves down to be heated. These rising and falling currents are known as convection cells.
Orion seen in Nottingham at 10pm, January 15, 2019. Credit: Daniel Brown
Each of these cells is only a few centimeters across in this example, but in Betelgeuse they are gigantic and moving much more slowly while interacting with the star's substantial magnetic field. Since the heat of the surface of the star determines its brightness, Betelgeuse shows a rather large variation of darker and brighter patches on its surface. As the star bubbles and rotates, we will see a slowly variable brightness, as we do now.
Another interesting feature is that the surface of Betelgeuse is rather cool, hence its red color. Because it has a huge radius, it also has a diminished gravitational grip on its outer surfaces. This means it loses some of its material—creating dusty clouds in its surroundings which could cause dimming as they move in front of the star.
You can monitor Betelgeuse's change in brightness yourself using only your eyes and no telescopes at all. In the northern hemisphere, Orion is observable during the first half of the night well into February. Compare Betelgeuse to other stars of different brightness to determine how bright it is. Pollux in Gemini is currently of similar brightness and Bellatrix in Orion is a bit fainter. The image below gives several other stars in and around Orion that can be used for comparison.
