It doesn’t take a rocket scientist to know that space is weird. But just how weird might surprise you?

One of these weird objects that makes you wonder, where did all the stars go, is a dark nebula, or absorption nebula. It is a type of interstellar cloud, particularly molecular clouds, that is so dense that it obscures the visible wavelengths of light from objects behind it, such as background stars and emission or reflection nebulae.

As a result, they scatter and absorb all input optical light, rendering them entirely impenetrable at visible wavelengths.

in the Wild Duck Cluster (M11). They cover the whole region, inky, starless zones of all shapes and depths that dot the Shield like Minnesota's 10,000 lakes.

These are massive clouds of interstellar dust and gas that hide the more distant stars, giving the appearance of holes in the Milky Way's starry fabric. They're formed of components comparable to brilliant nebulae like Orion or the Lagoon, but they don't have a nearby star or stars to light them up.

Although the density of these black clouds is only about 100-300 molecules per cubic centimetre, it mounts up over several light-years or more. Some black nebulae look practically invisible, with hardly a single star to break up the darkness.

One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, That no stars are visible in the centre indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light.

Another example is one of the most identifiable nebulae because of the shape of its swirling cloud of dark dust and gas. The Horsehead Nebula.

The Horsehead Nebula (Barnard 33) is a diffuse dark nebula located about 1500 light-years away in the constellation Orion, just to the south of the easternmost star in Orion’s Belt, Alnitak. The dark cloud of dust and gas is part of a region in the vast and complex Orion Nebula where star formation is taking place right now.

The dark molecular cloud is visible only because its obscuring dust is silhouetted against the bright red emission nebula IC 434. The Horsehead is a fascinating, active, and complex neighborhood.

Dark nebulae are critical to the universe's life cycle because they supply the raw materials for the next generation of stars and planets. Nothing could be further from the truth than the appearance that you are looking into emptiness.

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#darknebula #nebula #astronomy #space #spacenews

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