The Belt and the Sword

The magnificent Belt of Orion, a row of three equally brilliant stars blaze like a set of perfectly matched diamonds on a jeweler's cloth There is nothing like them in the sky. More than fifteen hundred light years away, they are all giant stars, tens of thousands of times brighter than the Sun.

Each is blazing at thirty thousand degrees. Each is more than ten times as massive as the Sun. But also, each is burning its fuel a thousand times faster than the Sun. Stars live by consuming the hydrogen of which theyıre made, and giant stars consume this fuel at an enormous rate. Their lifetimes are only a fraction of the Sun's.

A giant star is like a profligate who receives a large inheritance. His enormous wealth only fuels his desire to spend more, and he ends poor sooner than those who have less to spend.

The three of them are part of the great Orion association of brilliant stars. The stars of Orion are immersed in a giant cloud of hydrogen gas, and the belt was formed long ago when part of this cloud was compressed by the slowly turning arms of the Milky Way. But now, the brilliant stars of the belt themselves cause new star formation. Their outpouring of ultraviolet light now compress other parts of the cloud to form new stars.

You can see star formation going on right now in the magnificent Orion Nebula., Hanging below the belt of Orion is his mighty sword. What appears to be a star is in fact not a star at all. It is another part of gas cloud, compressed by the radiation of the hot young stars in it. Just as the belt of Orion once triggered star birth, now these stars fill that role. (You can see this cloud tonight using the simplest pair of binoculars, and even -- if you're keen sighted -- without any optical aid at all. Scan along the sword of Orion, below his belt.)

(12/12/07)