On 16 December 2009, the European Space Agency (ESA) reported that the Herschel Space Observatory has peered inside an unseen stellar nursery and revealed surprising amounts of activity. Some 700 newly-forming stars are estimated to be crowded into filaments of dust stretching through the image.
The image above shows a dark cloud 1000 light-years away in the constellation
Embedded within the dusty filaments in the
This cloud is part of Gould’s Belt, a giant ring of stars that circles the night sky – the Solar System just happens to lie near the centre of the belt. The first to notice this unexpected alignment, in the mid-19th century, was
Gould’s Belt supplies bright stars to many constellations such as Orion, Scorpius, Canis Major, Puppis, Carina, Centaurus, and Crux, and conveniently provides nearby star-forming locations for astronomers to study. Observing these stellar nurseries is a key programme for Herschel, which aims to uncover the demographics of star formation and its origin, or in other words, the quantities of stars that can form and the range of masses that such newborn stars can possess. Apart from this region of
More recent observations have established that the Gould Belt is a key structural feature of the Orion Arm, the region of the Milky Way Galaxy in which we live. It is an elliptical disk of hydrogen and other gases, inclined to the plane of the larger Galactic disk by an angle of about 17.2 degrees. Its long axis is about 750 parsecs, and its short axis is about 470 parsecs. Its age is estimated as 30 to 50 million years. In astronomical terms, therefore, the Gould Belt is a very young formation -- much more recent, for example, than the Jurassic Period (145-200 million years ago), when large dinosaurs roamed the Earth.
A recent theory is that the Gould Belt formed about 30 million years ago when a blob of dark matter collided with the molecular cloud in our region. There is also evidence for similar Gould belts in other galaxies.
The second full moon of December will fall on New Years Eve, a big, bright Blue Moon. A blue moon is a full moon that is not timed to the regular monthly pattern. Most years have twelve full moons which occur approximately monthly, but in addition to those twelve full lunar cycles, each calendar year contains an excess of roughly eleven days. The extra days accumulate, so that every two or three years (on average about every 2.7154 years), there is an extra full moon.
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