In the Spitzer image of NGC 1097, infrared light with shorter wavelengths is blue, while longer-wavelength light is red.
Credit: NASA/JPL-Caltech/The SINGS Team (SSC/Caltech)
A coiled galaxy with an eye-like object at its center harbors a hidden black hole surrounded by a storm of star formation.
The galaxy, called NGC 1097, is located 50 million light-years from Earth. It is spiral-shaped like our own Milky Way, with long, spindly arms of stars.
The "eye" at the center of the galaxy is caused by a monstrous black hole, which can't be seen but is surrounded by a ring of stars and rampant star birth. In a new color-coded infrared view from NASA's Spitzer Space Telescope, the area around the invisible black hole is blue and the ring of stars, white.
Black holes can't be seen because matter and light gets trapped in them. But they are identifiable by the gravitational interaction with their surroundings and the chaotic activity that goes on there.
The black hole is huge, about 100 million times the mass of our sun, and is feeding off gas and dust along with the occasional unlucky star. Our Milky Way's central black hole is tame in comparison, with a measly mass of just a few million suns.
"The fate of this black hole and others like it is an active area of research," said George Helou, deputy director of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena. "Some theories hold that the black hole might quiet down and eventually enter a more dormant state like our Milky Way black hole."
The ring around the black hole is bursting with new star formation. An inflow of material toward the central bar of the galaxy is causing the ring to light up with new stars.
"The ring itself is a fascinating object worthy of study because it is forming stars at a very high rate," said Kartik Sheth, an astronomer at NASA's Spitzer Science Center.
The galaxy's red spiral arms and the swirling spokes seen between the arms show dust heated by newborn stars. Older populations of stars scattered through the galaxy are blue. The fuzzy blue dot to the left, which appears to fit snuggly between the arms, is a companion galaxy.
"The companion galaxy that looks as if it's playing peek-a-boo through the larger galaxy could have plunged through, poking a hole," Helou said. "But we don't know this for sure. It could also just happen to be aligned with a gap in the arms."
This image was taken during Spitzer's "cold mission," which lasted more than five-and-a-half years. The telescope ran out of coolant needed to chill its infrared instruments on May 15, 2009. Two of its infrared channels will still work perfectly during the new "warm mission," which is expected to begin in a week or so, once the observatory has been recalibrated and warms to its new temperature of around 30 Kelvin (about minus 406 degrees Fahrenheit).
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