The brightest star in Orion's Sword
and the eighth brightest in the constellation of Orion.
Its Arabic name, Na'ir al Saif, means "the Bright One of the Sword."
Iota Ori is actually a complex quadruple star dominated by a 15-solar-mass
O star. At distances of 50" and 11", respectively,
lie an 11th magnitude class A or F dwarf and a 7th magnitude B star, with
true separations of at least 4,400 and 20,000 AU and orbital periods at
least 75,000 and 700,000 years. In addition, the O star has a B-type companion
in a highly eccentric 29-day orbit that varies from 0.8 AU to 0.11 AU from
the primary. At periastron, the centers
of the stars are separated only by about 1.5 times the sum of the radii,
which suggests that strong tidal forces will be generated and enhanced mass
loss may be expected. Colliding stellar
winds from the two giants generate powerful X-rays.
|From left to right, the Running Man Nebula, the Orion
Nebula, and Iota Orionis (brightest star on right-hand side). Credit:
Charlie Hein, Weston, FL
Iota Ori also has connections with two stars that lie well away from it
in our sky: fourth magnitude Mu Columbae, 26° to the south, and AE
Aurigae, 40° to the north. These two, almost identical in spectral
type to Iota Ori, are hurtling away from each other in opposite directions
at 200 km/s. They are runaway stars
and were apparently thrown out of the region of the Trapezium
cluster some 2.7 million years ago. According to one theory, they were once
part of a pair of tightly-knit binary stars. In a close encounter between
the two binaries, two of the four stars were ejected, while the remaining
two – the close O-B pair of Iota Ori – remained, more or less
at the site of the violent event.
||O9 III + B1 III
||R.A. 05h 35m 26s,
Dec. -05° 54' 36"
||Hatsya, Na'ir al Saif,
Hatysa in Becvar, 44 Orionis,
HR 1889, BD -06°1241,
HD 37043, SAO 132323,
ADS 4193, FK5 209,