Have you ever wondered what the night sky would look like around Vulcan, Tatooine, Alderan or Arakis? Would it look like the Earth’s night sky? Would you look up and see a dark sky with only a handful of very bright stars that stand out in a background of dim stars? Would you be able to recognise patterns of constellations in the sky that the small number of bright stars appear to trace out? Would you look up and see discernible patterns such as a snake like Draco, or a line like Orion’s belt? Also would the bright stars of the constellations themselves be concentrated in a belt like ring? Is the Earth’s night sky just like the night sky of all of these imaginary planets or their real analogues?
The answer to all of the above questions is a resounding NO. Almost all the night skies of planets orbiting distant stars fall into one of three basic patterns. Planets located in Galactic Nuclei (which constitute about 90% of stars) would see a very bright sky filled with millions of stars that all have just about the same brightness. Planets located in high gas areas such as spiral arms would see only a small number of randomly distributed dull stars. These constitute about about 8% of the remainder. The last approximately 2% would see a sky similar to the Solar System’s but it would look more like a wall paper made up of a uniform field of mixed bright and dull stars with few if any creating a discernible pattern.
As it turns out the Solar System, we are fortunate enough to inhabit, has a very rare sky and occupies a very unusual almost spooky position in space. Astronomers have discovered the Solar System sits in the middle of a very low density star bubble. This bubble is about 3000 light years across. It contains about a million low mass stars but only a few thousand high mass stars. Even stranger, these high mass stars are primarily located in a band called Gould’s Belt. Gould’s Belt is a ribbon of stars that make up the constellations of the night sky. This narrow band is tilted about 20 degrees to the plane of the Milky Way, our Galactic disk. It is the combination of low star density with a band of ultra bright stars concentrated in a belt which runs through it that provides the beautiful night skies peppered with constellations that the Earth’s inhabitants are allowed to enjoy.
These constellations have figured prominently in the history of the Earth. They have been useful tool to navigate on sea and land. They also have proven valuable to agriculturalists to mark out the farming labor cycles. The constellations have also figured prominently in the imagination of people all over the planet who used them as visual symbols of their mythology.
There is a second great mystery associated with the stars of Gould’s Belt. These stars seem to have been formed separately from the rest of the stars in our Galaxy. Stars are normally formed in the gas rich spiral arms. The stars in Gould’s Belt however seem to have been formed outside the spiral arms in “some local violent event.” This is truly a weird situation. The Earth sits in the middle of a peculiar bubble that seems to have been swept clear of most of the stars that were originally formed in it. The bubble was then surrounded by a unique ring of a few thousand bright stars that were formed in an unusual, possibly unique, event separately from all the other 200 million stars in this galaxy.
The title of this Blog was taken from the headline to the article which contained most of the information used in this Blog. The article however attempts to explain this amazing situation through the invocation of Dark Matter. At this time no one even knows if Dark Matter actually exists. Even if it is proven that Dark Matter exists and was the immediate cause of the wonderfully beautiful, glorious skies the Earth enjoys, would it not seem likely that the ultimate cause behind this incredible series of coincidences was the Hand of God?
Source: “Orion’s Dark Secret,” NewScientist, Nov. 21, 2009, pp 42-45.