Orion Nebula

Orion is a whole education in a single star system.

We've been enraptured by this most eye-catching of constellations since ancient times. It's a beautiful sight that dominates our winter skies in northern latitudes. The constellation was named after Orion the Hunter, a character in Greek mythology. But those ancient stargazers could never have dreamt of the tremendous details that modern astronomy has uncovered about this star system.

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A map of the stars in the constellation of Orion

© 2003 Torsten Bronger
Reproduced under the terms of the GNU Free Documentation License,
Wikimedia Commons, 2008

The ‘right shoulder’ of the ‘hunter’ is a star called Betelgeuse (sometimes pronounced ‘Beetlejuice’, but that's probably not the most correct way of saying it). This gargantuan star is a red supergiant and one of the largest stars known. It's so big, its diameter is larger than the orbit of Mars. That means, if we replaced our Sun with Betelgeuse, the star would swallow up Mercury, Venus, Earth and Mars.

It's very likely that Betelgeuse will soon explode and become a spectacular supernova. When it does so, a Betelgeuse supernova could easily outshine the Moon in our night sky. In fact, this could happen tomorrow: given that Betelgeuse is 640 light years away from Earth (which means that its light takes 640 years to get to reach us), it could have exploded 640 years ago, and we just don't know it yet.

The constellation's ‘left knee’ is the brilliant blue star called Rigel. The sixth brightest star in the sky, Rigel is a blue supergiant and — like Betelgeuse — bears a name which is derived from Islamic astronomy, since the Arabs made a great contribution to the subject, especially between the 8th and 16th Centuries.

But perhaps the jewel in the crown is Orion's great nebula. The nebula is an interstellar cloud of gas and dust, and is the closest region of star formation to the Earth. Recently, the Hubble Space Telescope took some fascinating pictures of the region and discovered stars and planetary systems in the making.

The excitement of this finding revolved around strange ‘proplyds’, as seen in the photograph below.

Photograph of proplyds in M42 taken by the Hubble Space Telescope

© C.R. O'Dell/Rice University; NASA

The proplyds are also known as ‘protoplanetary disks’. They are rotating disks around a new parent star: extrasolar systems in the making. The proplyds in Orion are solar system in size and very young, only a million or so years old. This is what a space artist thinks they look like up close:

An artist's impression of a protoplanetary disk.

© NASA

Could Orion's proplyds be another place where new life might develop?