The universe is so big, and changes so slowly, that astro-photographers only ever expect to record still images of their subjects. But when astronomers studying the supermassive black hole (SMBH) at the centre of the galaxy M87 noticed how fast it was expelling a jet of superheated gas, they commissioned time on the Hubble Space Telescope (HST) to make a movie. Specifically, they recorded 400 images over a period of 13 years and assembled them into a stop-motion video of the column of gas twisting and coiling as it jets out into space.
M87 is a giant elliptical galaxy, located some 54 million light years away, in the constellation Virgo. Like most galaxies, it’s been observed to have a vast black hole at its core, billions of times more massive than the Sun. As material falls inwards, its orbit spirals faster and faster, forming a superheated accretion disk. It has long been suspected that the SMBH’s powerful magnetic field scoops some of this material up and funnels it into very powerful, narrow jets aligned with its north and south poles, and it is these jets which are displayed in the movie. This is not the first such movie to be made, but it is the first with high enough resolution to show that the material is not flying straight out, but is spinning in a spiral track, confirming the magnetic hypothesis.
“Central supermassive black holes are a key component in all big galaxies,” said Eileen T. Meyer of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, the leader of the team which created the video. “Most of these black holes are believed to have gone through an active phase, and black-hole-powered jets from this active phase play a key role in the evolution of galaxies. By studying the details of this process in the nearest galaxy with an optical jet, we can hope to learn more about galaxy formation and black hole physics in general.”
“We analyzed several years’ worth of Hubble data of a relatively nearby jet, which allowed us to see lots of details,” Meyer said. “The only reason you see the distant jet in motion at all over just a few years is because it is traveling very fast.”
It took 8 months to make the video and produce the scientific results which were published in the August 22 online issue of The Astrophysical Journal Letters. They processed over 400 images, recoreded between 1995 and 2008 using Hubble’s Wide Field Planetary Camera 2 and Advanced Camera for Surveys. The video can be viewed below: