The Academy Awards doesn’t have a category for “Best Galaxy Jet in a Leading Role”, and that’s too bad. If they did give such an Oscar, a series of new movies captured by the National Science Foundation’s Very Large Baseline Array would make some fine nominees. Astronomers revisited the same galaxies for 15 years, capturing images of jets blasting out from their supermassive black holes. These images were then stitched together into a series of timelapse movies.
The jet study is known as MOJAVE (Monitoring of Jets in Active galactic nuclei with VLBA Experiments). This is actually the successor to a previous study that tracked more than 200 jets from 1994 to 2002.
The new survey used the National Science Foundation’s Very Long Baseline Array (VLBA). They made images of 200 galactic jets at regular intervals, tracking their motions and studying their magnetic-field properties. For 100 of these jets, they actually produced time-lapse movies, allowing them to show the speed and direction of motion.
Where do the jets come from? They originate around the supermassive black holes that lurk at the hearts of galaxies. Even though they weigh in with hundreds of millions of times the mass of the Sun, there’s only so much material they can gobble up at any one time. The material falls into a circular accretion disk orbiting the black hole. The magnetic fields generated by the rotating black hole propels material out jets from the poles of the disk.
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With long-term observations like this, the astronomers have been able to see how the jets change over time. Many have remained constant, but some have been surprisingly active. For some galaxies, the jets have brightened or dimmed over time. Others have changed course as the supermassive black hole’s magnetic field wrenched the particles into a new direction. Jets have been seen to split apart.
If you want to see what a movie of a galactic jet looks like, check out this link for some animations.
Original Source: Purdue News Release