Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

August 18, 1998

APM 08279+5255: The Brightest Object Yet Known
Credit: M.J. Irwin (RGO), E.J. Totten (Keele U.) et al., Isaac Newton 2.5-m Telescope

Explanation: It shines with the brightness of 100 billion Suns. Is it a mirage? The recently discovered quasar labeled APM 08279+5255 has set a new record as being the brightest continuously emitting object yet known. APM 08279+5255's great distance, though, makes it only appear as bright as magnitude 15.2, an object which can be seen with a moderate sized telescope. It is the quasar's extreme redshift of 3.87 that places it far across our universe, and implies a truly impressive energy output. One possible explanation of APM 08279+5255's record luminosity is that it is partly a mirage: its light is highly magnified by an intervening galaxy that acts as a gravitational lens. Alternatively, APM 08279+5255 might be the most active known centre of an intriguing class of colliding galaxies rich in gas and dust.

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