An experimental fix that astronauts made in March to the Hubble Space Telescope's broken infrared camera has it working better now than when it was new.
Hubble scientists unveiled new images from the camera yesterday and told astronomers meeting in Albuquerque, N.M., that the repairs to the Near Infrared Camera and Multi-Object Spectrometer have made it 30 percent to 40 percent more sensitive than when it was installed in the orbiting observatory in 1997.
That means it can see that much deeper, through opaque clouds of dust and gas, into the turbulent cores of colliding galaxies and the hearts of stellar nurseries.
"It's a fantastic instrument," said Ed Cheng, Hubble development project scientist at NASA's Goddard Space Flight Center in Greenbelt. "It's performing as expected, and better than it used to be."
One of the first NICMOS images taken since the repair, released yesterday, shows a region of intense star formation near the center of a spiral galaxy 55 million light-years from Earth.
In visible light, the galaxy looks like the Milky Way, which we see edge-on in a dark night - a ribbon of dark dust and glowing starlight.
But because NICMOS is sensitive to infrared radiation, which penetrates much of the dust, its new image of the same galaxy reveals a narrow band of bright, yellow light deep inside the galaxy.
"NICMOS peered all the way through to the center of the galaxy, and you can see what we believe is star formation at the nucleus," said Daniela Calzetti, who coordinates the work of NICMOS scientists for the Space Telescope Science Institute in Baltimore.
Astronomers believe the prolific star formation - a thousand times faster than in a comparable area of the Milky Way - is occurring in a ring that orbits the hub of the galaxy. They presume it's a ring because they see similar structures in many other spiral galaxies that can be seen from a different angle.
"The key to that image is the idea that we are able to penetrate to the core of that galaxy for the first time - to see to the core of an edge-on galaxy," Cheng said.
It's a little like seeing into the filling of a jelly doughnut from the side, without having to take a bite. The revived infrared camera will enable astronomers to learn things about the interior workings of edge-on galaxies that would otherwise have been inaccessible to them.
NICMOS' new lease on life came in March, when astronauts making their mission's fifth spacewalk installed a high-tech refrigeration system needed to cool the instrument's infrared detectors.
The original cooling system, a block of nitrogen ice, had failed in 1999, after just two years in orbit. The ice "sublimated" - turned to gas and escaped into space - prematurely.
Since the astronauts installed it, the new system has chilled the NICMOS detectors to 77 degrees Kelvin - about 321 degrees below zero Fahrenheit, Calzetti said. And it is holding the temperatures steady to within one-tenth of a degree.
"It is performing extremely well," she said.
The 77-degree temperature allows NICMOS' detectors to operate at their peak sensitivity. The old cooler made them too cold, 61 degrees K, and the thermostat could not be turned up.
The second of three new images released yesterday (viewable on the Web at www.stsci.edu/resources/) demonstrates that power.
It shows the narrow end of the Cone Nebula, a dense, cone-shaped cloud of dust and gas, 2,500 light-years from Earth in our own Milky Way galaxy.
Seen through an optical telescope, the nebula resembles rough mountain terrain. NICMOS penetrates much of that landscape to reveal a dozen points of light that appear to be newborn stars embedded in the nebula that gave them birth. (More study is needed to be sure the stars are not actually beyond the nebula.)
The third new NICMOS image shows four galaxies in collision a billion light-years from Earth. Seeing through the dust and gas at the center of this galactic merger, NICMOS unveils a region of intense star formation that holds clues to the forces at work there, and to how such galaxies evolve.