GRAFFIAS (Beta Scorpii). Graffias, in the head of the celestial Scorpion and Scorpius's Beta star, has at least two names and many more components. "Graffias," meaning "claws," originally referred to the "real" claws that are now in Libra, Zubenelgenubi and Zubeneschamali. But in more modern times the name was given first -- and unaccountably -- to obscure Xi Scorpii and then to our star, Beta Scorpii. An equally common name is "Acrab," from Arabic, meaning "the scorpion," older ideas strongly relating crabs with scorpions. Though bright, just at the end of second magnitude, Graffias is still only the sixth brightest star in this brilliant constellation, the Beta designation probably a result of the star's prominent position. It is wonderfully complex. Through a small telescope we see a classic double star, the components 14 seconds of arc apart, similar to the separation of those that make Mizar in the Big Dipper. The brighter and more westerly, Beta-1, is just over the line into third magnitude (2.62), the fainter, Beta-2, is mid-fifth magnitude (4.92). At a distance of 530 light years, the two are at least 2200 astronomical units apart and take over 16,000 years to orbit each other. Both are hot class B stars, Beta-1 the hotter with a temperature of around 27,000 Kelvin, Beta-2 closer to 22,000. Though both should appear blue-white to the eye, the brightness difference makes them look different through the telescope, the fainter one seeming a bit ashen, rather yellowish. The fun begins with closer examination. Beta-1 has a tenth magnitude closer companion only half a second of arc (projected 80 astronomical units) away, so Graffias now seems triple. More, Beta-1 proper (the brighter) is a "spectroscopic binary," the spectrum showing two stars in orbit with a period of 6.8 days, the separation a mere 0.001 seconds, 0.3 AU, closer than Mercury is from the Sun. Still more, Beta-2 has a fainter companion a tenth of a second away from it. Graffias is at least a quintuple star, and there are suggestions of more pieces. All five except perhaps for the faint companion of Beta-2 are hot B stars, vividly showing their propensity for multiple birth. The brightest, the chief star of the Beta-1 triple, is over 20,000 times the solar luminosity (after correction for interstellar dust absorption). What a sight it would be from an "earth" orbiting Beta-1 and its two companions, say at 150 astronomical units where we could survive. We would have a triple Sun, and off in the distance the double Beta-2 would shine 50 times brighter than our full Moon. Both of the Beta-1 close pair are over 10 times as massive as the Sun, and both will probably explode sometime in the next few million years. Scorpius and its neighboring constellations are filled with stars like these. Some of what we know of the system came from a rare occultation (covering) by Jupiter in 1971, Beta-2 by Jupiter's satellite Io.
Written by Jim Kaler. Return to STARS.