Picture Scramble # 75

22 January 2001

For astronomers, Orion is one of the most important constellations, as it contains one of the nearest and most active stellar nurseries in the Milky Way, the galaxy in which we live.

Here tens of thousands of new stars have formed within the past ten million years or so - a very short span of time in astronomical terms. For comparison: our own Sun is now 4,600 million years old and has not yet reached half-age. Reduced to a human time-scale, star formation in Orion would have been going on for just one month as compared to the Sun's 40 years.

Just below Orion's belt, the hilt of his sword holds a great jewel in the sky, the beautiful Orion Nebula. Bright enough to be seen with the naked eye, a small telescope or even binoculars show the nebula to be a few tens of light-years' wide complex of gas and dust, illuminated by several massive and hot stars at its core, the famous Trapezium stars.

However, the heart of this nebula also conceals a secret from the casual observer. There are in fact about one thousand very young stars about one million years old within the so-called Trapezium Cluster, crowded into a space less than the distance between the Sun and its nearest neighbour stars.