blue star near the center of this image is Zeta Ophiuchi. When seen in
visible light it appears as a relatively dim red star surrounded by other
dim stars and no dust. However, in this infrared image taken with NASA's
Wide-field Infrared Survey Explorer, or WISE, a completely different view
emerges. Zeta Ophiuchi is actually a very massive, hot, bright blue star
plowing its way through a large cloud of interstellar dust and gas.
Astronomers theorize that this stellar juggernaut was likely once part
of a binary star system with an even more massive partner. It's believed
that when the partner exploded as a supernova, blasting away most of its
mass, Zeta Ophiuchi was suddenly freed from its partner's pull and shot
away like a bullet moving 24 kilometers per second (54,000 miles per hour).
Zeta Ophiuchi is about 20 times more massive and 65,000 times more luminous
than the Sun. If it weren't surrounded by so much dust, it would be one
of the brightest stars in the sky and appear blue to the eye. Like all
stars with this kind of extreme mass and power, it subscribes to the 'live
fast, die young' motto. It's already about halfway through its very short
8-million-year lifespan. In comparison, the Sun is roughly halfway through
its 10-billion-year lifespan. While the Sun will eventually become a quiet
white dwarf, Zeta Ophiuchi, like its ex-partner, will ultimately die in
a massive explosion called a supernova.
Perhaps the most interesting features in this image are related to the
interstellar gas and dust that surrounds Zeta Ophiuchi. Off to the sides
of the image and in the background are relatively calm clouds of dust,
appearing green and wispy, slightly reminiscent of the northern lights.
Near Zeta Ophiuchi, these clouds look quite different. The cloud in all
directions around the star is brighter and redder, because the extreme
amounts of ultraviolet radiation emitted by the star are heating the cloud,
causing it to glow more brightly in the infrared than usual.
Even more striking, however, is the bright yellow curved feature directly
above Zeta Ophiuchi. This is a magnificent example of a bow shock. In
this image, the runaway star is flying from the lower right towards the
upper left. As it does so, its very powerful stellar wind is pushing the
gas and dust out of its way (the stellar wind extends far beyond the visible
portion of the star, creating an invisible 'bubble' all around it). And
directly in front of the star's path the wind is compressing the gas together
so much that it is glowing extremely brightly (in the infrared), creating
a bow shock. It is akin to the effect you might see when a boat pushes
a wave in front it as it moves through the water. This feature is completely
hidden in visible light. Infrared images like this one from WISE shed
an entirely new light on the region.
The colors used in this image represent specific wavelengths of infrared
light. Blue and cyan (blue-green) represent light emitted at wavelengths
of 3.4 and 4.6 microns, which is predominantly from stars. Green and red
represent light from 12 and 22 microns, respectively, which is mostly
emitted by dust.