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.