- Astronomers are looking at stars and galaxies in the night sky. The stars are the sources of light in the Universe. It seems unusual that astronomers can also be studying dark objects in the night sky.
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- The Globules are dark clouds in space that are often silhouetted by light emissions in the background. The dark clouds are called Bok Globules after the Dutch-American astronomer Bart Bok.
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- Astronomers have located about 100 of these globules in the Milky Way Galaxy. However, they expect there are 10,000’s more whose silhouettes we just can not see.
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- Most globules are about 30,000 AU in diameter. An AU is an astronomical unit of distance that is the distance between the Earth and the Sun, 93 million miles. So, these globules are 30,000 times larger then the orbit of the Earth. Our entire Solar System is 60 AU across.
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- Globules appear as dark clouds , however, these are very, very light clouds. The air we breath is 100,000,000,000 times denser then these clouds. But, if you were inside one of these globules it would be totally dark. No star light would penetrate far into the cloud of gas and dust grains.
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- Two of the most famous globules are the Horsehead Nebula, ( B33) and the Eagle Nebula ( M16)
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- These nebulae globules are star forming regions that astronomers are studying. Stars form from the fragmentation and eventual collapse of interstellar molecular clouds. The collapse of clouds is usually caused by shockwaves from nearby supernova explosions.
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- The Bok Globule Bernard 68 is in the Constellation Ophiuchus, The Serpent Bearer, and is between 100,000 and 1,000,000 years old. It is 350 lightyears from Earth. The temperature of the cloud has been measured to be 10 Kelvin. The surrounding interstellar medium is 50 Kelvin.
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- Bernard 68 is oscillating like a beating heart which is believed to have been caused by being hit by something. The globule is denser towards the center than on the edges which suggest it is slowly collapsing into a star. Calculations are that in another 100,000 years B68 will be a low mass Red-Dwarf star.
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- Other globules suggest that multiple star formations are common. Star formations may take a few million years. The outward push of heated gas balances the inward pull of gravity. The core can reach a few thousand Kelvin causing molecules of hydrogen to break down into individual atoms of hydrogen. Gravity will eventually win, a protostar will form, and nuclear fusion will light up the star. A star is born.
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- Globules are chemically rich. The gas inside the globules freezes into dust grains. An analogy would be blowing your breath on a cold window and the frost will form on the window. Ultraviolet radiation will break down the dust grains into molecules that can come back together to form new compounds. Laboratories that try to simulate this process have created protein molecules and even cell membranes. If it can happen in the lab maybe it can happen in space.
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- Some of the compounds that have been identified in globules include methanol, carbon dioxide, and ammonia.
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- This is exciting stuff to study. Astronomers are building more sensitive spectroscopy equipment in the hopes of detecting complex organic molecules. Globules are good for study and hopefully easier to understand that the giant molecular clouds that form hundreds of star clusters.
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An announcement will be made shortly, stay tuned
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