Pasadena, CA— Blazars are the brightest of active galactic nuclei, and many emit very high-energy gamma rays. New observations of a blazar known as PKS 1424+240 show that it is the most-distant known source of very high-energy gamma rays. But its emission spectrum appears highly unusual.
A team including Carnegie’s Michele Fumagalli used data from the Hubble Space Telescope to set a lower limit for the blazar's redshift (z ≥ 0.6035). An object’s redshift value is a measurement of how much the wavelength of the light from it that reaches Earth is stretched by the expansion of the Universe. Thus, it reveals the object’s age and distance. This blazar’s redshift corresponds to a distance of at least 7.4 billion light-years. Their work will be published by The Astrophysical Journal Letters and is available online.