APOD: The Central Magnetic Field of the... (2019 Mar 11)

[APOD Robot]

The Central Magnetic Field of the Cigar Galaxy

Explanation: Are galaxies giant magnets? Yes, but the magnetic fields in galaxies are typically much weaker than on Earth's surface, as well as more complex and harder to measure. Recently, though, the HAWC+ instrument onboard the airborne (747) SOFIA observatory has been successful in detailing distant magnetic fields by observing infrared light polarized by reflection from dust grains. Featured here, HAWC+ observations of the M82, the Cigar galaxy, show that the central magnetic field is perpendicular to the disk and parallel to the strong supergalactic wind. This observation bolsters the hypothesis that M82's central magnetic field helps its wind transport the mass of millions of stars out from the central star-burst region. The featured image shows magnetic field lines superposed on top of an optical light (gray) and hydrogen gas (red) image from Kitt Peak National Observatory, further combined with <a href"https://www.esa.int/Our_Activities/Spac ... e_infrared" >infrared images</a> (yellow) from SOFIA and the Spitzer Space Telescope<a/>. The <a href="ap130704.html">Cigar Galaxy is about 12 million light years distant and visible with binoculars towards the constellation of the Great Bear.

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[bystander]

viewtopic.php?t=39231

[Boomer12k]

This is an interesting concept...

:---[===] *

[Ann]

APOD Robot wrote:

Featured here, HAWC+ observations of the M82, the Cigar galaxy, show that the central magnetic field is perpendicular to the disk and parallel to the strong supergalactic wind. This observation bolsters the hypothesis that M82's central magnetic field helps its wind transport the mass of millions of stars out from the central star-burst region.

Click to view full size image

The central magnetic field of the Cigar galaxy.
NASA, SOFIA, E. Lopez-Rodriguez; NASA, Spitzer, J. Moustakas et al

Click to view full size image

Inner disk and jet of M87.
Holland Ford, Space Telescope Science Institute/Johns Hopkins University; Richard Harms,
Applied Research Corp.; Zlatan Tsvetanov, Arthur Davidsen, and Gerard Kriss
at Johns Hopkins; Ralph Bohlin and George Hartig at Space Telescope
Science Institute; Linda Dressel and Ajay K.Kochhar at Applied Research Corp.
in Landover, Md.; and Bruce Margon fromthe University of Washington in Seattle NASA/ESA

Interesting. Isn't that how jets from supermassive black holes get going?

Ars Technica wrote:

At the centers of some massive galaxies, supermassive black holes power incredibly bright objects called quasars. Black holes gobble up matter so quickly that the infalling matter heats up from friction and emits light. While this disk of accreting matter is incredibly bright on its own, the black hole has another source of light: jets erupt from the poles of the black hole, shooting particles at speeds approaching that of light. These jets are incredibly bright—possibly brighter than the accretion disk.

It’s not known for sure what causes the jets. It’s thought that the black hole’s spin and mass interact with the magnetic field near the black hole to accelerate the particles. While some evidence supports this model, it's been difficult to test, mainly because scientists lacked a full knowledge of how bright the accretion disks is. But a new study of a sample of blazars (quasars with jets that point toward Earth) shows a clear correlation between the jets' power and the accretion disk’s brightness. This suggests that the magnetic field is a factor in producing the jets.

But in the case of M82, it seems to be the wind from the extreme starburst at the center of the galaxy that powers both the magnetism and the outflow of gas. That may be why the outflow from M82 is relatively "broad", and not long and narrow, as seems to be the case of black hole-powered jets.

Ann

[heehaw]

Very impressive!

[orin stepanek]

I wonder if man may someday ride these magnetic currents for space travel?

[Chris Peterson]

I wonder if man may someday ride these magnetic currents for space travel? :rocketship:

Keep in mind that if you chuck a refrigerator magnet out in front of your spacecraft, its magnetic field will overwhelm the local field of the galaxy. It's like having a ship on stormy seas and hoping to ride on the current of a goldfish.

[Cousin Ricky]

Why is there a square around the Milky Way star to the lower right of the galaxy?

[Chris Peterson]

Why is there a square around the Milky Way star to the lower right of the galaxy?

I'd assume it was selected out for separate processing- compensation for saturation or blooming, perhaps. The star to the lower right also shows some kind of artifact.

[JohnD]

By a "square" do you mean the "diffraction spikes".
They are commonly seen in astronomcal photographs, and the brighter the star, the more prominent, and that's the brightest in the pic.
There's an excellent example, top right, on the Wiki page: https://en.wikipedia.org/wiki/Diffraction_spike
The spikes are an artefact, but not significant of a need for special processing are they, Chris?

[Chris Peterson]

By a "square" do you mean the "diffraction spikes".
They are commonly seen in astronomcal photographs, and the brighter the star, the more prominent, and that's the brightest in the pic.
There's an excellent example, top right, on the Wiki page: https://en.wikipedia.org/wiki/Diffraction_spike
The spikes are an artefact, but not significant of a need for special processing are they, Chris?

There is an actual square region around the star with a different background brightness. It might not be obvious, or even visible, if your monitor's black level is too high.

[danhammang]

First, kudos to the folks at APOD. It's an interesting pic captured by instrumentation on a program, SOFIA, that I was not aware of. Another of the bewildering array of space research programs. And secondly, kudos to the folks behind the pic. It's an impressive effort of pulling together data from different sources...and offered freely for our edification. Many thanks to everybody involved. Thank you once again Drs. Nemiroff and Bonnell. Don't know how you are able to crank 'me out day after day...

[Odysseus]

SOFIA observatory has been successful in detailing distant magnetic fields by observing infrared light polarized by reflection from dust grains.

Why is it that magnetic fields need illumination to be detectable? How are light and dust grains affected by these magnetic fields.

[neufer]

---

SOFIA observatory has been successful in detailing distant magnetic fields by observing infrared light polarized by reflection from dust grains.

Why is it that magnetic fields need illumination to be detectable? How are light and dust grains affected by these magnetic fields.

• Magnetic fields align small dust grains with other small dust grains over large scales.
  
  Those small dust grains produce polarized light (either by radiation or absorption).
  
  We can observe & measure such light polarized over large scales from far away.

[Chris Peterson]

SOFIA observatory has been successful in detailing distant magnetic fields by observing infrared light polarized by reflection from dust grains.

Why is it that magnetic fields need illumination to be detectable? How are light and dust grains affected by these magnetic fields.

Magnetic fields don't need illumination to be detectable. But if we're detecting them by optical methods (as is the case here), something either has to reflect light or produce it.

[Guest]

Just wondering. If a black hole has infinite mass, and therefore cannot exist in our 'interpretation' of reality, then how can it have 'spin' as we understand it? Kind of the same question as 'was there time before the big bang' type of argument. Without a frame of reference, given infinite density of a super massive black hole, it kind of makes me wonder about our real understanding of physics/space/time/energy & matter, But still a great image.

[Chris Peterson]

Just wondering. If a black hole has infinite mass, and therefore cannot exist in our 'interpretation' of reality, then how can it have 'spin' as we understand it? Kind of the same question as 'was there time before the big bang' type of argument. Without a frame of reference, given infinite density of a super massive black hole, it kind of makes me wonder about our real understanding of physics/space/time/energy & matter, But still a great image.

Black holes don't have infinite mass.

[JohnD]

Thanks, Chris! Can't see it, but I'll take your word for it!
John

[Chris Peterson]

Thanks, Chris! Can't see it, but I'll take your word for it!
John

Here it is with the contrast stretched. In addition to the square around the star, we can also see what look like blooming repairs on the left and right sides, outside the square (or maybe additional diffraction spikes from one of the other instruments that collected the data were removed).

In any case, it's not surprising to see these sorts of processing artifacts in an image made from multiple data sources.
_

square_close.jpg (10.71 KiB) Viewed 3940 times

[Cousin Ricky]

Just wondering. If a black hole has infinite mass, and therefore cannot exist in our 'interpretation' of reality, then how can it have 'spin' as we understand it? Kind of the same question as 'was there time before the big bang' type of argument. Without a frame of reference, given infinite density of a super massive black hole, it kind of makes me wonder about our real understanding of physics/space/time/energy & matter, But still a great image.

As Chris said, they do not have infinite mass. According to general relativity, they do have infinite density, but this is ipso facto precisely where general relativity theory fails. As a non-expert, I suspect that they have a mind-bogglingly high non-infinite density that will be answered by some future theory of quantum gravity.

[MarkBour]

It's a beautiful image.

I'm not in the league with those who did this study, but as a layman, I'm still wondering if there is some circular reasoning involved here. If they start with the fact that a force is moving large amounts of mass perpendicular to the galaxy, then any non-spherical dust grain would have a tendency for its alignment to correlate with the direction of the flow, in many different causal scenarios. The statistical alignment of the dust grains is what the polarized light is actually showing, right? So, they seem to be claiming that they've detected a magnetic field because of the alignment, and then saying that this gives support for the idea that the magnetic field is helping cause the flow.

I must have missed something essential?