Astronomers using the Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes (ALMA, APEX, the IRAM 30-m telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope) — have revealed a new view of the supermassive black hole at the center of Messier 87, a giant elliptical galaxy located some 53 million light-years from us in the constellation of Virgo. This is the first time astronomers have been able to measure polarization, a signature of magnetic fields, this close to the edge of a black hole.
This EHT image shows the polarized view of the black hole in Messier 87. The lines mark the orientation of polarization, which is related to the magnetic field around the shadow of the black hole. Image credit: EHT Collaboration.
On April 10, 2019, the EHT Collaboration released the first ever image of a black hole, revealing a bright ring-like structure with a dark central region — the black hole’s shadow.
Since then, the astronomers have delved deeper into the data on the supermassive black hole at the heart of Messier 87 collected in 2017.
The newest EHT images are a key to explaining how the black hole, called M87*, can launch energetic jets.
“There is a supermassive black hole at the center of almost every galaxy,” said Professor Gopal Narayanan, a researcher at the University of Massachusetts Amherst and a member of the EHT Collaboration.
“These black holes power the galactic nuclei, which often launches high energy jets from the central parts of the galaxy.”
“Understanding the physics connecting supermassive black holes and galactic jets has been difficult. That is where light polarization comes in.”
“This work is a major milestone: the polarization of light carries information that allows us to better understand the physics behind the image we saw in April 2019, which was not possible before,” said Dr. Iván Martí-Vidal, an astronomer at the University of Valencia and a member of the EHT Collaboration.
“Unveiling this new polarized-light image required years of work due to the complex techniques involved in obtaining and analyzing the data.”
“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets,” said Dr. Monika Mościbrodzka, an astronomer at Radboud University and a member of the EHT Collaboration.
“One of the main science drivers of the EHT is distinguishing different magnetic field configurations around the black hole,” said Dr. Angelo Ricarte, an astronomer at the Harvard & Smithsonian Center for Astrophysics.
“Polarization is one of the most direct probes into the magnetic field that nature provides.”
This composite image shows three views of the central region of Messier 87 in polarized light and one view, in the visible wavelength, taken with the NASA/ESA Hubble Space Telescope. The Hubble image at the top captures a part of the jet some 6,000 light-years in size. Image credit: EHT Collaboration / ALMA / ESO / NAOJ / NRAO / Goddi et al. / NASA / ESA / Hubble Heritage Team / STScI / AURA / VLBA / Kravchenko et al. / J.C. Algaba / I. Martí-Vidal.
M87* has a mass of 6.5 billion solar masses. Material drawn inward forms an accretion disk closely orbiting the black hole. Most of the material in the disk falls into the black hole, but some surrounding particles escape and are ejected far out into space in jets moving at nearly the speed of light.
“The newly published polarized images are key to understanding how the magnetic field allows the black hole to ‘eat’ matter and launch powerful jets,” said Dr. Andrew Chael, an astronomer at the Princeton Center for Theoretical Science and the Princeton Gravity Initiative and a member of the EHT Collaboration.
The EHT researchers compared the new images that showed the magnetic field structure just outside the black hole with computer simulations based on different theoretical models.
They found that only models featuring strongly magnetized gas can explain what they are seeing at the event horizon.
“The observations suggest that the magnetic fields at the black hole’s edge are strong enough to push back on the hot gas and help it resist gravity’s pull,” said Dr. Jason Dexter, an astronomer at the University of Colorado Boulder and a member of the EHT Collaboration.
“Only the gas that slips through the field can spiral inwards to the event horizon.”
“This first polarized image of the black hole in M87 is just the beginning,” said Dr. Dominic Pesce, an astronomer at the Harvard & Smithsonian Center for Astrophysics and a member of the EHT Collaboration.
“As the EHT continues to grow, future observations will refine the picture and allow us to study how the magnetic field structure changes with time.”
“Even now we are designing a next-generation EHT that will allow us to make the first black hole movies. Stay tuned for true black hole cinema,” said Dr. Sheperd Doeleman, founding director of the EHT.
The new results are published in three papers in the Astrophysical Journal Letters.
_____
Kazunori Akiyama et al. (The Event Horizon Telescope Collaboration). 2021. First M87 Event Horizon Telescope Results. VII. Polarization of the Ring. ApJL 910, L12; doi: 10.3847/2041-8213/abe71d
Kazunori Akiyama et al. (The Event Horizon Telescope Collaboration). 2021. First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon. ApJL 910, L13; doi: 10.3847/2041-8213/abe4de
Ciriaco Goddi et al. 2021. Polarimetric Properties of Event Horizon Telescope Targets from ALMA. ApJL 910, L14; doi: 10.3847/2041-8213/abee6a
