In the last year, astronomers from Wyoming Uni have discovered 100 of the fastest-moving stars in the Milky Way galaxy with NASA’s Spitzer Space Telescope and Wide-field Infrared Survey Explorer (WISE), and use of the Wyoming Infrared Observatory (WIRO) on Jelm Mountain, Wyo.
When some swift, massive stars – moving at > 50,000 miles/h- plow through space, they can cause material to stack up in front of them in the same way that water piles up ahead of a ship or a supersonic plane creates a shockwave in front of it. Called bow shocks, these dramatic arc-shaped features in space are helping researchers to uncover massive, so-called runaway stars. “Some stars get the boot when their companion star explodes in a supernova, and others can get kicked out of crowded star clusters,” says William Chick. “The gravitational boost increases a star’s speed relative to other stars.”
These are hot, massive stars that are moving through interstellar space at supersonic speed.
Kobulnicky says they use the bow shocks to locate these 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,” he says.
Earth’s sun moves around the Milky Way at a moderate pace, but it is not clear whether it 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 the sun, at 54,000 mph (24 kilometers per second) relative to its surroundings. 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 20X as massive as Earth’s sun, has supersonic winds that slam into the material in front of it.
When a massive star with fierce winds like Zeta Oph zips through space, it forms a pile-up of material that glows. This arc-shaped material heats up and shines with infrared light that is assigned the color red in the many pictures of bow shocks captured by Spitzer and WISE.
The death of supernovas is responsible for most of the heat created in the galaxy, half of all elements heavier than helium and half of all iron that resides in the human race. These stars are 5-6 times hotter than the sun, which is 5,500C
Chick and his team used archival infrared data from Spitzer and WISE to identify new bow shocks, including more distant ones that are more difficult to locate. Their initial search turned up more than 200 images of fuzzy red arcs. They then used WIRO to follow up on 80 of these candidates and identify the sources behind the suspected bow shocks. Most turned out to be massive stars.
While some of the stars may indeed be fast-moving runaways that were given a gravitational kick by other stars, in a small fraction of the cases, the arc-shaped features may turn out to be something else: dust from stars, or birth clouds of newborn stars. The team plans more observations to confirm the presence of the bow shocks. http://www.uwyo.edu/uw/news/2016/01/uw-researchers-discover-runaway-stars-leave-infrared-waves-in-space.html
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