Shadow of black hole in M87 galaxy is wobbling and has been for a while


Date:
September 23, 2020
Source:
Center for Astrophysics, Harvard & Smithsonian (CfA)
Summary:
A new analysis reveals the behavior of the supermassive black hole
in the center of the M87 galaxy across multiple years, indicating
the crescent- like shadow feature appears to be wobbling.



FULL STORY ========================================================================== Analysis of previously unpublished data from observations of M87*
between 2009 and 2013 by scientists at the Event Horizon Telescope
(EHT) has revealed that the crescent shadow of the black hole is
wobbling, and has rotated significantly over the past ten years of
observation. Published today in The Astrophysical Journal, and led by scientists from the Center for Astrophysics | Harvard & Smithsonian
(CfA), the study focused on the morphology of the black hole over time,
and was made possible by advances in analysis and understanding achieved
as a result of EHT's groundbreaking black hole photo in 2019.


==========================================================================
"EHT can detect changes in the M87 morphology on timescales as short as a
few days, but its general geometry should be constant on long timescales,"
said Maciek Wielgus, an astronomer at CfA, Black Hole Initiative (BHI)
Fellow, and lead author on the paper. "In 2019, we saw the shadow
of a black hole for the first time, but we only saw images observed
during a one-week window, which is too short to see a lot of changes." Combining previous data from 2009-2013 with data leading up to 2019
revealed that M87* adheres to theoretical predictions. The shape of the
black hole's shadow has remained consistent, and its diameter remains in agreement with Einstein's theory of general relativity for a black hole
of 6.5-billion solar masses. "In this study, we show that the general morphology, or presence of an asymmetric ring, most likely persists
on timescales of several years," said Kazu Akiyama, a scientist at the
MIT Haystack Observatory, and a participant on the project. "This is an important confirmation of theoretical expectations as the consistency throughout multiple observational epochs gives us more confidence
than ever about the nature of M87* and the origin of the shadow."
While the crescent diameter remained consistent, new data also proves
it was hiding a surprise: the ring is wobbling, and that means big news
for scientists. For the first time, scientists will be able to catch a
glimpse of the dynamical structure of the black hole's accretion flow;
studying this region holds the key to understanding phenomena like
launching relativistic jets. "The morphology of a relativistic jet --
low density outflow of tremendously energetic particles and fields -- for example, is key to understanding the interactions with the surrounding
medium in a black hole's host galaxy," said Richard Anantua, a postdoc
at the Center for Astrophysics | Harvard & Smithsonian and BHI Fellow,
adding that studying morphology weaves an important story about black
holes and their hosts.

The gas falling onto a black hole heats up to billions of degrees, ionizes
and becomes turbulent in the presence of magnetic fields. This turbulence causes the appearance of the black hole to vary over time. "Because
the flow of matter falling onto a black hole is turbulent, we can
see that the ring wobbles with time," said Wielgus. "The dynamics of
this wobbling will allow us to constrain the accretion flow." Anantua
added that it is important to constrain accretion flows because, "The
accretion flow contains matter than gets close enough to the black
hole to allow us to observe the effects of strong gravity, and in some circumstances, allows us to test predictions from general relativity,
like we've done in this study." In the current study, multiple years of
data allow scientists to perceive the amount of variability in the ring's appearance. "Actually, we see quite a lot of variation there, and not all theoretical models of accretion flow allow for this much variability,"
said Wielgus. "As we obtain more measurements in the future, we will be
able to confidently put constraints on models and rule some of them out."
Early data in the EHT collaboration were taken by just a few telescopes
and a few dozen people. The CfA's Submillimeter Array (SMA) -- a radio telescope located on Mauna Kea, Hawai'i -- was among the small group
that started the collaboration and captured the early data used for
the current study. Simon Radford, Operations Director at the SMA said,
"Hawai'i telescopes pioneered this technique over the past decade and
were crucial to the success of early EHT experiments," adding that the combination of the technology, telescopes, and location are what made
the early data useful and meaningful.

Ten years later the data has become an invaluable tool to understanding
not only M87, but all black holes. "These early EHT experiments provide
us with a treasure trove of long-term observations that the current EHT,
even with its remarkable imaging capability, cannot match," said Shep
Doeleman, Founding Director, EHT. "When we first measured the size of
M87 in 2009, we couldn't have foreseen that it would give us the first
glimpse of black hole dynamics.

If you want to see a black hole evolve over a decade, there is no
substitute for having a decade of data." Wielgus added that the continued analysis of past observations, along with new observations "will lead to a better understanding of the dynamical properties of M87, and black holes
in general." The EHT and many of its key scientists are supported with
funding from public entities, including the National Science Foundation
and the Smithsonian Institution and from private entities including the
John Templeton Foundation and the Gordon and Betty Moore Foundation.


========================================================================== Story Source: Materials provided by Center_for_Astrophysics,_Harvard_&_Smithsonian_(CfA).

Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* Snapshots_and_animation_from_observations_of_M87*_black_hole ========================================================================== Journal Reference:
1. M. Wielgus et al. Monitoring the Morphology of M87* in 2009-2017
with the
Event Horizon Telescope. The Astrophysical Journal, 2020; 901 (1):
67 DOI: 10.3847/1538-4357/abac0d ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200923124636.htm

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