First Blazar

StarDate

Earth faces a non-stop barrage of particles from a supermassive black hole at the heart of a giant galaxy. Fortunately, it’s almost a billion light-years away – not close enough to cause any problems.

BL Lacertae is in Lacerta, the lizard. The constellation is in the east-northeast at nightfall, to the left of the Great Square of Pegasus. It passes high overhead around midnight. Its stars are all so faint that you need fairly dark skies to see any of them.

At first, BL Lac appeared to be one of those faint stars – much too faint to see without a telescope. It was discovered almost a century ago. It gets brighter and fainter over a period of a few days, so it was classified as a variable star.

In the late 1960s, though, astronomers realized that BL Lac is far outside the Milky Way Galaxy. It’s a beam of energy from a black hole at the center of a giant galaxy.

Gas funnels into the black hole. But powerful magnetic fields channel some of that material back into space. It forms “jets” of charged particles that beam into the universe at close to the speed of light. And one of those jets takes dead aim at Earth.

BL Lac is the prototype of a whole class of black holes with jets aimed our way. In fact, it even gave the name to a new category of objects. The name combines BL Lac with “quasar” – a similar type of object – to make “blazar” – supermassive black holes blazing across the universe.

Script by Damond Benningfield