A Runaway Star

Most stars move through the galaxy in an orderly fashion, bobbing along and slowly revolving about the galactic center like a perpetual cosmic merry-go-round. But once in awhile a star takes a faster ride when it’s slingshotted across the sky by a close gravitational interaction with another star. There are dozens of these “runaway” stars visible in the heavens. One of the best-known lies in the constellation Auriga, the Charioteer. This blazing star, called AE Auriga, had its origins in a famous nebula before it was flung into the Orion Arm of the Milky Way…

AE Aurigae is a blazing-blue main sequence star 17 times more massive than our Sun and 30,000 times as luminous. Astronomers have traced back the motion of AE Aur to a spot in the Orion Nebula, a cloud of glowing gas which you can easily see with binoculars in the “sword” of Orion. The star may was ejected about 2 million years ago, perhaps by a close gravitational interaction of two multiple star systems. Another possibility: the stars were ejected by the gravitational effects of a supernova explosion, the same explosion that formed the elegant nebulous arc known as Barnard’s loop.

The constellation Orion and Barnard’s Loop

Whatever happened to AE Aur, it was not alone in its fate: two other fast-moving stars also trace their origins to the Trapezium about 2 million years ago: the deep-southern star mu Columbae and the star 53 Arietis.

For such an intrinsically bright star, AE Aur doesn’t look like much. That’s partly because it’s quite far, about 1,500 light years, and also because it’s dimmed by interstellar dust which knocks down the star’s brightness by nearly a full magnitude.

AE Aurigae (also cataloged as HD 34078) is particularly interesting for stargazers because it’s passing through an unrelated cloud of interstellar gas and dust which the star sets aglow with its brilliant blue and UV light. The result is the Flaming Star Nebula, also called IC 405. Here’s a recent image of IC 405 from NASA’s Astronomy Picture of the Day (APOD).

(Publisher’s Note: You can learn more about the Flaming Star Nebula and more than 100 other deep-sky objects in the guide “What To See in a Small Telescope: January to March”. To learn more about this guide, click here…)

Red circles mark the position of AE Aurigae and IC 405. Click to enlarge.