Brightest Pearl

(Click image for larger view)
One of the first constellations I memorized as a child was Orion’s Belt. Those 3 stars were easily discernable in the winter sky. I used to take my Dad’s binoculars and let my view fall below the belt to the sword. In time I would locate a visual treasure, Orion's nebula. Little did I realize at that time, but a magnificent pearl was right before my eyes at the end of Orion’s Belt. Alnitak, or Zeta Orionis, is the left hand star of the 3 stars of the belt. The ancient Arabs called these stars the “belt of al jauza’ or the “string of pearls”. Alnitak is the brightest class O star in the sky, a hot blue supergiant. The region around Alnitak is remarkable as well, containing several dusty clouds of interstellar gas, including the famed "Horsehead Nebula" to the south. The nose of the horse can just be seen in the lower left corner of the image. Also of interest is the Flame Nebula, or NGC 2024, to the right of Alnitak. Seven molecular dust clouds work their way like tendrils into the Flame Nebula. The red glow of the Nebula would indicate that Hygrogen gas has been ionized and is recombining with it’s lost electrons. But from what star? Recent infrared studies confirm what scientists have assumed for some years, that several young hot stars are hidden beneath the dust clouds, and are the source of energy for ionizing the gas.

Alnitak is the central theme of this image and rightfully so. It approaches first magnitude even though at a distance of 800 light years. It is 10,000 times more luminous than the Sun. However, its 31,000 Kelvin surface radiates mostly in the ultraviolet where the eye cannot see, and when that it taken into account, Alnitak's luminosity climbs to 100,000 times solar. A planet like Earth would have to be 300 times farther from Alnitak than Earth is from the Sun (8 times Pluto's distance) for life like ours to survive. Such brilliance can only come from a star of great mass, Alnitak's estimated to be about 20 times larger than our sun. Like all O stars, Alnitak is a source of X-rays. These seem to come from a wind that blows from its surface at nearly 2000 kilometers per second. X-rays are produced when blobs of gas in the wind crash violently into one another.

Image acquisition info-

Location: Starlodge Observatory
Date: Jan 2007
Camera: ST-10XME
Scope: Takahashi FSQ 106
Mount: Paramount ME
LRGB data: 200:130:100:145 all binned 1x1