In new research, astronomers used images of bow shocks – glowing, arc-shaped features in space – to find dozens of so-called runaway stars, the fastest stars in our galaxy.
Bow shocks are created when speedy, massive stars plow through space and cause material to stack up in front of them in the same way that water piles up ahead of the bow of a ship.
University of Wyoming astronomer William Chick presented the new results yesterday (January 5, 2015) at the American Astronomical Society (AAS) meeting in Kissimmee, Florida. In a statement, Chick said:
Some stars get the boot when their companion star explodes in a supernova, and others can get kicked out of crowded star clusters. The gravitational boost increases a star’s speed relative to other stars.
Our own sun is strolling through our Milky Way galaxy at a moderate pace, say the researchers, and it is not clear whether our sun creates a bow shock. By comparison, a massive star with a stunning bow shock, called Zeta Ophiuchi (or Zeta Oph), is traveling around the galaxy faster than our sun, at 54,000 mph (24 kilometers per second) relative to its surroundings. (See Zeta Oph’s giant bow shock in the image at the top of the page.)
Both the speed of stars moving through space and their mass contribute to the size and shapes of bow shocks. The more massive a star, the more material it sheds in high-speed winds. Zeta Oph, which is about 20 times as massive than our sun, has supersonic winds that slam into the material in front of it.
The result is a pile-up of material that glows. The arc-shaped material heats up and shines with infrared light.
The researchers looked at archival infrared data from from NASA’s Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE) to identify new bow shocks, including more distant ones that are harder to find. Their initial search turned up more than 200 images of fuzzy red arcs. They then used the Wyoming Infrared Observatory, near Laramie, to follow up on 80 of these candidates and identify the sources behind the suspected bow shocks. Most turned out to be massive stars.
The findings suggest that many of the bow shocks are the result of speedy runaways that were given a gravitational kick by other stars. However, in a few cases, the arc-shaped features could turn out to be something else, such as dust from stars and birth clouds of newborn stars. The team plans more observations to confirm the presence of bow shocks.
University of Wyoming astronomer Henry “Chip” Kobulnicky said:
We are using the bow shocks to find massive and/or runaway stars. The bow shocks are new laboratories for studying massive stars and answering questions about the fate and evolution of these stars.
Bottom line: In new research presented January 5, 2015 at the American Astronomical Society (AAS) meeting in Kissimmee, Florida, astronomers used images of bow shocks – glowing, arc-shaped features in space – to find dozens of so-called runaway stars, the fastest stars in our galaxy.