Iota Orionis, the bright star to the lower right of center in this image of the Orion Nebula, is actually a binary--two stars locked in orbit around each other by their mutual gravitational pull. While the stars in most binaries are the same age, indicating that they were born together, the stars of Iota Orionis are different ages. That suggests that each star was born with another partner. A close encounter between the two binaries sent one member of each pair flying through the galaxy, with the remaining members latching on to each other and forming a new binary. [rawastrodata]
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Iota Orionis AB is unlike most other binary star systems. While the stars in most binaries are the same age, the stars of Iota Orionis AB are not. That suggests that its two stars formed separately, and somehow managed to grab onto each other.
The mechanism for that embrace might have been an encounter with two other stars — both of which are now racing across the galaxy at hundreds of thousands of miles per hour.
Iota Orionis is at the tip of Orion’s Sword, which hangs below his three-star belt at nightfall. The star is near the Orion Nebula, a stellar nursery. The nebula and related clouds of gas and dust have given birth to thousands of stars, including those of Iota Orionis.
The region is crowded, so there are frequent encounters among stars.
A few million years ago, there might have been an encounter between two binaries. The four stars — all much bigger, brighter, and heavier than the Sun — danced a complicated ballet. During that dance, one star from each pair switched partners, forming Iota Orionis. The two abandoned stars were given a gravitational kick — they were expelled from the region around the Orion Nebula at high speed.
Today, one of those stars is far south of Orion, in Columba, the dove, which is low above the southern horizon. The other star is far north of Orion, in Auriga, the charioteer, which stands high overhead. These stars are runaways from their stellar birthplace, kicked out by their siblings.
Script by Damond Benningfield