You are here


March 23, 2018

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

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.