Hercules A, also known as 3C 348, lies around two billion light-years away. It is one of the brightest sources of radio emission outside our Galaxy. It’s the bright object at the middle of the frame, an elliptical galaxy. As seen in visible light by the Hubble Space Telescope it appears floating serenely in the inky blackness of space, but adding data from a radio telescope radically transforms the image. Jets of material can be seen billowing outwards from the galaxy when viewed at radio frequencies—jets that are completely undetectable in visible light. The image above combines data from the Very Large Array radio observatory in New Mexico with data from Hubble‘s Wide Field Camera 3.
The two jets are composed of hot, high-energy plasma that has been flung from Hercules A by a supermassive black hole lurking at the galaxy’s core. This black hole is roughly 2.5 billion times the mass of the Sun. That’s about a thousand times more massive than the black hole at the centre of the Milky Way.
Hercules A’s black hole accelerates the ejected material to nearly the speed of light, sending it flying out into intergalactic space. Eventually, the highly focused jets lose energy, slowing down and spreading out to form cloud-like blobs The multiple bright rings and knots seen within these blobs suggest that the black hole has sent out successive bursts of material. The jets stretch for around 1.5 million light-years, around 15 times the size of the Milky Way.
Image Credit: NASA / ESA / VLA