A "hole" in space

Researchers aren't 100 percent certain what formed the so-called Local Bubble, but it's looking more like a nearby supernova-of the violent Type-II variety-excavated the hole. The Local Bubble is a vast "hole" that was opened in the interstellar medium that surrounds our Sun; it extends for over 1,000 light-years in at least one direction.

The resulting blast punched through the interstellar dust and gas that originally surrounded our local region of space. Think of a fireball of a thermonuclear nuclear device but on a vast interstellar scale. As the shockwave front of a Type-II fireball spreads out into deep space, it blows away everything in its path.

Ironically, astronomers have benefited from the Local Bubble. Because our local region of space has been swept clear of much of its dust and gas, deep-sky telescopic observing has offered a "clearer" view in the direction of the bubble's point of origin; we'd never have known this fact if we didn't, first, have the understanding of looking out from inside this Local Bubble. Also, if we didn't have astronomical instruments capable of observing space in the extreme ultraviolet (UV) region of the electromagnetic spectrum, we probably wouldn't have been able to discover the Local Bubble in the first place.

Back in 1975, astronomers first noticed that, in wavelengths ranging from 10 to 100 nm, short-wavelength photons were ionizing neutral hydrogen atoms. This evidence suggested that some kind of a monster "hole" or bubble existed in the space around our solar system.

The Local Bubble extends 1,000 light-years (300 parsecs) in the direction of the star Beta Canis Majoris in the constellation Canis Major. In 1992, NASA's Extreme Ultraviolet Explorer spacecraft was the first to map the Local Bubble. At the same time, the European ROSAT spacecraft detected a pulsating beam of X-rays that strongly suggested a possible point of origin for the bubble in space.

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