Most Luminous Galaxy Really Isn't a Galaxy

An object once thought to be the brightest in the heavens has been revealed as a gravitational lens by new infrared images from the Keck Telescope in Hawaii.

Since its discovery in 1991 the object has been heralded as a rare primordial galaxy or protogalaxy emitting energy as new stars form from swirling clouds of gas.

Training the telescope on the object, Berkeley astronomers James R. Graham and graduate student Michael Liu saw a distant object bent into an arc centered on a nearer massive galaxy along the same line of sight from Earth.

They then subtracted from the image the bright foreground galaxy, revealing a second faint image on the side opposite the much brighter arc. According to the theory of gravitational lenses, a pair of images like this should straddle the foreground object.

"Its identification as the most luminous galaxy...was an astronomical blooper," says Graham, an associate professor of astronomy. "Nature always makes things messy, but more interesting." --R.S.


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