Image: National Astronomical Observatory of Japan/Subaru Telescope
The Suprime-Cam, a wide field camera for visible light, on the Subaru Telescope in Mauna Kea is a powerful tool for spotting new galaxies--and in the course of a recent analysis, it did just that. The instrument can capture a 24 by 24 arcminute square of the sky, an area almost as large as the full moon (see image), thanks to the telescopes primary mirror, which measures more than four meters in diameter. And its resolution, in this case about 0.6 arcsconds, is limited only by Earth's atmosphere above the Hawaiian peak. Because more than 70 percent of the light entering the telescope is detected, even the faintest objects are recorded. Here these objects are about 100 million times fainter when viewed with the naked eye.
The new galaxies--a cluster some 5 billion light years away--appear in the center of the magnified image, shown to the right of the original above. The builders of Suprime-Cam identified them amidst the 30,000 plus objects in the main picture. The brightest objects are faint stars in our own Milky Way galaxy; the streaks are artifacts created when the instrument's electronic detectors are over-exposed. Their primary task has been uncovering large-scale structure in the universe by way of the "weak lensing" method. The technique relies ongravitational lensing, the phenomenon by which light from distant objects is bent by the gravity of closer objects. Measuring this distortion of distant features allows the researchers to approximate the gravitational influence, and so mass, of nearer galaxies--and thus get a better sense of the distribution of mass throughout the universe.