Scientists map magnetic fields of Milky Way's Black Hole: Is it SANE or MAD?

Original source (on modern site) | Article images: [1]

Black Hole- a name that intrigues anyone intrigued in the cosmic drama. It intrigued scientist Stephen Hawking, it continues to catch the attention of generations after. In a recent development, scientists have been able to take a closer look at the Sagittarius A, black hole in our galaxy--Milky Wat. Researchers and observers have also been able to map the monstrous magnetic fields of the black hole, which is four million times more massive than the Sun.

One cannot see the black hole, Sagittarius A. Rather a shadow of a lightless bubble nested within the 'accretion disk' is visible.

The global network of radio observatories called the Event Horizon Telescope (EHT), have been able to achieve the breakthrough of mapping Sagittarius A. Scientists hope to do much more in the coming decade with an more advanced EHT.

What are Black Holes?

Black Holes remain an unfathomable mystery that increases every time one puzzle is solved. Black Holes have been credited of powering the most energetic phenomena in the known universe, from quasars to gamma-ray bursts.

They can be formed from a single star or weigh in at billions of stellar masses.

Further supermassive Black Holes are responsible in shaping the structure and flow of matter within their home galaxies. This also makes for an interesting research point of Sagittarius A's contribution in Milky Way.

Supermassive black hole accretes matter, the energy released in the form of high-energy radiation can heat up and redistribute the surrounding gas—affecting, among other things, galactic rates of star formation.

Have human's seen Black Holes?

Only two Black Holes have made it into the EHT's high-resolution photo album: Sagittarius A and the even larger M87, a 6.5-billion-solar-mass gargantuan at the center of Messier 87, or M87, a giant elliptical galaxy some 55 million light-years from Earth.

The first snapshot came in 2019 when the EHT released an image of the plasmatic torus encircling M87.

In 2022 the EHT followed suit with Sagittarius A.

Why are these visuals important?

In 2021 researchers announced that they had measured how light is polarized across M87's inner accretion disk, which let them chart the magnetic fields around the black hole.

Now the EHT team has done the same for Sagittarius A* and detailed its results in two studies recently published in the Astrophysical Journal Letters.

What does the Study say?

The thousandfold mass difference between Sagittarius A and M87 explains why the latter's magnetic underpinnings were seen first. Because our own galaxy's central black hole is roughly a thousand times less massive than M87, the churning maelstrom around Sagittarius A can change about a thousand times faster, too: features that may persist for days around M87 can come and go in mere minutes around Sagittarius A.

Despite the differences in mass and M87's prominent, iconic jet, the polarized light detected by the EHT around each supermassive black hole shows a striking similarity with profound implications: both boast accretion disks shaped by strong, ordered magnetic fields.

This proves if Black Holes are SANE OR MAD?

Collectively, the EHT's studies to date point toward an answer to a longstanding debate in astrophysics: Do the accretion flows around black holes tend to be SANE, or are they MAD?

Under the SANE (standard and normal evolution) model of accretion flows, magnetic fields around a black hole are relatively weak and constantly jostled by swirling, turbulent plasma within the accretion disk.

In MAD (magnetically arrested disk) models, however, magnetic fields can be stronger and play a dominant role in shaping a black hole's accretion disk, corralling the plasma into more orderly arrangements.

Black Holes with MAD-like magnetic fields are particularly efficient at generating huge jets of charged particles, like the cosmic blowtorch that stretches out for thousands of light-years from M87.

For both M87* and Sagittarius A, the EHT's polarization data suggest a highly ordered magnetic structure, favoring the MAD model.

(With inputs from the study)

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Published: 17 Apr 2024, 04:50 PM IST

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