Young Active Galaxy with ‘TIE Fighter’ Shape
This illustration shows two views of the active galaxy TXS 0128+554, located around 500 million light-years away. Left: The galaxy’s central jets appear as they would if we viewed them both at the same angle. The black hole, embedded in a disk of dust and gas, launches a pair of particle jets traveling at nearly the speed of light. Scientists think gamma rays (magenta) detected by NASA’s Fermi Gamma-ray Space Telescope originate from the base of these jets. As the jets collide with material surrounding the galaxy, they form identical lobes seen at radio wavelengths (orange). The jets experienced two distinct bouts of activity, which created the gap between the lobes and the black hole. Right: The galaxy appears in its actual orientation, with its jets tipped out of our line of sight by about 50 degrees.
Credit: NASA’s Goddard Space Flight Center
Not so long ago, astronomers mapped a galaxy far, far away using radio waves and found it looked strikingly similar to Darth Vader’s TIE fighter spacecraft in “Star Wars: Episode IV – A New Hope.” In the process, they discovered the object, called TXS 0128+554, experienced two powerful bouts of activity in the last century.
Around five years ago, NASA’s Fermi Gamma-ray Space Telescope reported that TXS 0128+554 (TXS 0128 for short) is a faint source of gamma rays, the highest-energy form of light. Scientists have since taken a closer look using the Very Long Baseline Array (VLBA) and NASA’s Chandra X-ray Observatory.
TXS 0128 lies 500 million light-years away in the constellation Cassiopeia, anchored by a supermassive black hole around 1 billion times the Sun’s mass. It’s classified as an active galaxy, which means all its stars together can’t account for the amount of light it emits.
Researchers added the galaxy to a long-running survey conducted by the VLBA, a network of radio antennas operated by the National Radio Astronomy Observatory stretching from Hawaii to the U.S. Virgin Islands.
The array’s measurements provide a detailed map of TXS 0128 at different radio frequencies. The radio structure they revealed spans 35 light-years across and tilts about 50 degrees out of our line of sight. This angle means the jets aren’t pointed directly at us and may explain why the galaxy is so dim in gamma rays.
The radio emission also sheds light on the location of the galaxy’s gamma-ray signal. Many theorists predicted that young, radio-bright active galaxies produce gamma rays when their jets of high-energy particles collide with intergalactic gas. But in TXS 0128’s case, at least, the particles don’t produce enough combined energy to generate the detected gamma rays. Instead, Lister’s team thinks the galaxy’s jets produce gamma rays closer to the core, like the majority of active galaxies Fermi sees.
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