News and commentary about the Great Frontiers

ISS007-E-10807 (21 July 2003) --- This view of Earth's horizon as the sunsets over the Pacific Ocean was taken by an Expedition 7 crewmember onboard the International Space Station (ISS). Anvil tops of thunderclouds are also visible. Credit: Earth Science and Remote Sensing Unit, NASA Johnson Space Center

Image Credit: ISS007-E-10807 (21 July 2003) – Earth Science and Remote Sensing Unit, NASA Johnson Space Center

Clear to the Center of the Milky Way



The clearest image yet (above left, compare to image above yet) of the center of our galaxy has been captured by the 10-meter Keck II Telescope at the W.M. Keck observatory in Hawaii. The image show the area surrounding Sagittarius A*, the name given to the energy source believed to be a black hole at the center of the Milky Way. This new clarity has allowed scientists to better characterize the black hole and energy flares in its vicinity. The results are published online and in an upcoming issue of ApJ in the paper “The First Laser Guide Star Adaptive Optics Observations of the Galactic Center: Sgr A*’s Infrared Color and the Extended Red Emission in its Vicinity“.

Black holes remain cyphers due to their very nature. Because not even light can escape the gravitational tug of these bodies, by definition they cannot be seen directly. Activity in the space surrounding black holes, however, led to their discovery and provided astrophysicists with data to better explain the phenomena. As matter interacts violently with a black hole’s event horizon (the sphere of “no return”) it releases energy. Images at various wavelengths were taken of Sagittarius A* to better characterize this released energy.

The latest imaging feat was accomplished by using a breakthrough technology called Laser Guide Star adaptive optics. A laser pointing up from the observatory creates an artificial point of light in the Earth’s upper atmosphere. This virtual star helps the instrument adapt to changing atmospheric conditions to produce images undistorted by the intervening atmosphere. Adaptive optics has emerged in the last decade as a technique for improving Earth-based telescopes beyond the capabilities of even space telescopes like Hubble.

Adaptive optics and related techniques continue to progress rapidly and over the next few years several projects around the world will see existing telescopes outfitted and new telescopes standardized with the technology.

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