Like a supersonic jet flying through the atmosphere, fast stars push interstellar material aside, which can create spectacular bow shock images.
A team of astronomers from the University of Wyoming have looked through archival data from NASA's Spitzer and WISE telescopes to identify such bow shocks. Out of the 200 fuzzy arc-shaped clouds associated with bow shocks discovered, they followed up 80 of them and identified the culprit behind the bow shocks: Most of them were produced by massive "runaway" stars.
"Some stars get the boot [from other stars] when their companion star explodes in a supernova, and others can get kicked out of crowded star clusters," said astronomer William Chick, who presented his team's new results at the American Astronomical Society meeting in Kissimmee, Florida, in a statement.
"The gravitational boost increases a star's speed relative to other stars."
As a speedy massive star moves through the interstellar medium, it causes material to stick up in front of it, like waves in front of the bow of a ship. The piled-up material starts heating up and it shines with infrared light that is then detected by the space observatories.
"We are using the bow shocks to find massive and/or runaway stars," said astronomer Henry "Chip" Kobulnicky. "The bow shocks are new laboratories for studying massive stars and answering questions about the fate and evolution of these stars.”
Bow shocks thought to mark the paths of massive, speeding stars are highlighted in these images from NASA's Spitzer Space Telescope and WISE. NASA/JPL-Caltech/University of Wyoming
Although many of the bow shocks are formed by runaways stars, arc-shaped features that resemble bow shocks could also be dust expelled from stars and stellar nurseries.
Another team, led by Cintia Peri of the Argentine Institute of Radio Astronomy, has been using the complete opposite approach to detecting bow shocks. They first selected speedy massive stars and then looked for bow shock signatures using Spitzer and WISE.
"WISE and Spitzer have given us the best images of bow shocks so far," said Peri. "In many cases, bow shocks that looked very diffuse before can now be resolved, and, moreover, we can see some new details of the structures."
Chick and his team are now planning to follow-up on other targets, and are hoping to detect more massive stars.