Black Hole Eats and Erupts!

The only reason we can see black holes in the universe is because some of them swallow up gas and dust.  This heats up material that is spinning rapidly around the black hole as it falls in (called an accretion disk), and produces massive jets of material due to conservation of angular momentum that can be seen across the universe.  The energy released in the jets and the energy given off in the accretion disk are proportional to how much gas and dust is being consumed by the black hole.  More matter = more food = more energy released.  But what happens when a black hole swallows up a bigger, denser object like a star?  The results are truly monstrous.

This artists impression shows a black hole consuming a star that has been torn apart by the black hole’s strong gravity. As a result of this massive “meal” the black hole begins to launch a powerful jet that we can detect with radio telescopes. Credit: NASA/Goddard Space Flight Center/Swift

Astronomers at John’s Hopkins University have used a suite of group-based telescopes to conduct follow up observations of a rare event: A black hole swallowing an entire star.  The event was first imaged in December 2014, and has since been looked at by radio, X-ray, and optical telescopes, giving a multi-wavelength view.

The now non-existent star was similar in size to the Sun, and when swallowed up by the black hole, the resulting blast of energy from the jet was easily noticeable in Earth-based telescopes.  “These events are extremely rare,” said Sjoert van Velzen, a Hubble fellow at Johns Hopkins. “It’s the first time we see everything from the stellar destruction followed by the launch of a conical outflow, also called a jet, and we watched it unfold over several months.”

Black hole jet in distant galaxy. Credit:

A jet forms when a large amount of plasma enters the black hole, in this case from a star.  A stream of elementary particles near the edge are blasted away in a strong magnetic field, perpendicular to the disk of the black hole.  This jet can be seen from incredible distances.

Seeing these rare events can help us to understand the mechanics of black holes, how they form jets, how they swallow up material, and how they grow and affect their environment.




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