Cygnus A

StarDate

Deneb, the brightest star of Cygnus, stands high overhead as night falls at this time of year. And it really is a brilliant star – tens of thousands of times brighter than the Sun. But if we could tune our eyes to see radio waves, Deneb wouldn’t even register. Instead, the swan’s leading light would be Cygnus A – one of the brightest radio galaxies in the universe.

A radio galaxy produces huge amounts of radio waves. It’s usually a large elliptical galaxy, which looks like a fat, fuzzy football. It has a supermassive black hole at its center.

Gas, dust, and stars spiral into the black hole. But powerful magnetic fields eject some of that material back into space. It forms “jets” that fire out at almost the speed of light. The jets can span hundreds of thousands of light-years. Electrons spiral through a jet’s magnetic field, producing radio waves. Eventually, the jets plow into gas and dust between galaxies, forming wide bubbles that emit even more radio waves.

Cygnus A was the first radio galaxy ever discovered, in 1939. It’s about 760 million light-years away. Its black hole is two and a half billion times the mass of the Sun. The entire complex – galaxy, jets, and bubbles – spans more than 600,000 light-years. That’s six times the diameter of our home galaxy, the Milky Way – one of the biggest, brightest radio galaxies in our part of the universe.

More about radio galaxies tomorrow.

Script by Damond Benningfield