The Event Horizon Telescope has outdone itself once again. Five years after releasing the world’s first-ever image of a black hole, the international network of radio observatories has published a more detailed depiction of M87*, a black hole at the center of galaxy M87. Not only does the “new” snapshot offer astronomers and amateur skygazers the opportunity to visualize an incredibly elusive phenomenon, but it also expands the scope of possibility for the world’s most powerful ground observatories.
The EHT Collaboration published its original M87* image in 2019, but the observations that image was built upon were conducted in April 2017. Back then, the EHT consisted of eight sites around the world. Using an atomic clock to synchronize each site’s telescope within a fraction of a millimeter, these sites spent four days collecting 5 petabytes of data from M87*. It’s this data that resulted in the composite set of images published in April 2019. Before then, astronomers had only “seen” black holes indirectly via peripheral data, so even a relatively blurry “fiery donut” was enough to wow the scientific community and the general public.
A year after its 2017 observations, though, the EHT set about capturing M87* all over again. This time, it incorporated the Greenland Telescope, a 39-foot-wide radio observatory operating at the Thule Air Base. In a blog post from Thursday titled “M87* One Year Later,” the EHT Collaboration published its updated snapshot of the world’s most recognizable black hole.
The 2018 composite depicts M87* in all its familiar glowing glory, but this time, we’re able to catch a glimpse of a few extra features. The dark shadow at the center of M87* is sharper than before, and as the EHT points out, the brightest part of the ring has shifted counterclockwise by about 30 degrees. While the EHT hasn’t yet managed to observe the jet of radiation spewing from M87*, it has confirmed that the black hole spin axis predicted via the structure’s brightest region is consistent with the jet axis seen at other wavelengths.
“The biggest change, that the brightness peak shifted around the ring, is actually something we predicted when we published the first results in 2019,” Dr. Britt Jeter, a postdoctoral fellow at Taiwan’s Academia Sinica Institute for Astronomy and Astrophysics, said on behalf of the EHT. “While general relativity says the ring size should stay pretty fixed, the emission from the turbulent, messy accretion disk around the black hole will cause the brightest part of the ring to wobble around a common center. The amount of wobble we see over time is something we can use to test our theories for the magnetic field and plasma environment around the black hole.”
