The Nautical Almanac # 16 --- Betelgeuse, the Giant's Hand

 

Betelgeuse is the sixteenth star in the Nautical Almanac. Lying due opposite of Bellatrix as seen from Earth, it designates the right shoulder of Orion The Hunter. The name is a corruption the Arabic Yad al-Jauza, "The Giant's Hand." 

Betelgeuse is the second brightest star in Orion, and has been known to mankind since we descended from the trees --- perhaps before. Mythologically and astrologically, it is a Behenian star associated with tempests and wars, but also great fame. The ancient Greeks believed that Orion had been stung to death by Scorpius, and so red Betelgeuse is linked with the red star Antares in the Greek cosmology, as well as with the planet Mars. It is also associated with the Spring planting, since it rises highest in the sky in early Springtime. Farmers used to awaken just as Betelgeuse (and Bellatrix) reached their zeniths, at about 3:00 AM around the time of the vernal Equinox. 

Betelgeuse is huge. Were it our sun it would envelope all the inner planets, the asteroid belt, and Jupiter as well. If Betelgeuse were a football stadium, the Sun would be a large mango, and the Earth a ball bearing. 

Betelgeuse lies some 660 light years from the Earth and is a variable star, between 90,000 and 150,000 times as bright as our Sun. It has about ten times the mass of the Sun, and is estimated to have begun with 20 times the mass. It is less than 10 million years old, as opposed to our Sun's 4.5 billion years. It is only about 6000 degrees F., as opposed to the Sun's 10,000 degrees. 

Betelgeuse is racing through the heavens at more than 67,000 mph, a runaway star from the OB1 Association within Orion. Betelgeuse is moving so fast that it has formed a bow wave and a long wake of interstellar material. Betelgeuse is also shrinking fast. It has lost 15 percent of its mass in just 25 years. It is believed that the red supergiant has exhausted all of its gases and lighter elements, leaving only iron to burn. Because it is ejecting so much material and is moving so fast, the star is deformed, with a huge bulge on one side of its disk (clearly to be seen in the photo). Once it burns enough iron, the star will collapse on itself and explode (supernova). 

Scientists believe that the star is close to a supernova state, that indeed it may have already exploded (if it were to explode today it would take nearly 700 years for the light of the starburst to be visible to us). If the star explodes (or has exploded) Betelgeuse is not close enough for its x-rays, ultraviolet radiation, gamma radiation or ejected material to cause major effects on the Earth.