The 'Eye of Sauron'

Mar 11, 2011
Credits: X-ray: NASA/CXC/CfA/J.Wang et al.; Optical: Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope, Radio: NSF/NRAO/VLA

( -- Spiral galaxy NGC 4151 is dubbed the "Eye of Sauron" for its similarity to the malevolent eye in "The Lord of the Rings."

This composite image shows the central region of the NGC 4151, dubbed the "Eye of Sauron" by astronomers for its similarity to the eye of the malevolent character in "The Lord of the Rings". In the "pupil" of the eye, X-rays (blue) from the Chandra X-ray Observatory are combined with (yellow) showing positively charged hydrogen ("H II") from observations with the 1-meter Jacobus Kapteyn Telescope on La Palma. The red around the pupil shows neutral hydrogen detected by radio observations with the NSF's Very Large Array. This neutral hydrogen is part of a structure near the center of NGC 4151 that has been distorted by with the rest of the galaxy, and includes material falling towards the center of the galaxy. The yellow blobs around the red ellipse are regions where has recently occurred.

A recent study has shown that the X-ray emission was likely caused by an outburst powered by the located in the white region in the center of the galaxy. Evidence for this idea comes from the elongation of the X-rays running from the top left to the bottom right and details of the X-ray spectrum. There are also signs of interactions between a central source and the surrounding gas, particularly the yellow arc of H II emission located above and to the left of the black hole.

Two different scenarios to explain the X-ray emission have been proposed. One possibility is that the central black hole was growing much more quickly about 25,000 years ago (in Earth's time frame) and the radiation from the material falling onto the black hole was so bright that it stripped electrons away from the atoms in the gas in its path. X-rays were then emitted when electrons recombined with these ionized atoms.

The second possibility also involved a substantial inflow of material into the black hole relatively recently. In this scenario the energy released by material flowing into the black hole in an accretion disk created a vigorous outflow of gas from the surface of the disk. This outflowing gas directly heated gas in its path to X-ray emitting temperatures. Unless the gas is confined somehow, it would expand away from the region in less than 100,000 years. In both of these scenarios, the relatively short amount of time since the last episode of high activity by the black hole may imply such outbursts occupy at least about 1% of the black hole's lifetime.

NGC 4151 is located about 43 million light years away from the Earth and is one of the nearest galaxies which contains an actively growing black hole. Because of this proximity, it offers one of the best chances of studying the interaction between an active supermassive black hole and the surrounding gas of its host galaxy. Such interaction, or "feedback", is recognized to play a key role in the growth of supermassive and their host galaxies. If the X-ray emission in NGC 4151 originates from hot gas heated by the outflow from the central black hole, it would be strong evidence for feedback from active black holes to the surrounding gas on galaxy scales. This would resemble the larger scale feedback, observed on galaxy cluster scales, from active black holes interacting with the surrounding gas, as seen in objects like the Perseus Cluster.

These results were published in the August 20, 2010 issue of The Astrophysical Journal Letters. The authors were Junfeng Wang and Giuseppina Fabbiano from the Harvard Smithsonian Center for Astrophysics (CfA), Guido Risaliti from CfA and INAF-Arcetri Observatory, in Firenze, Italy, Martin Elvis from CfA, Carole Mundell from Liverpool John Moores University in Birkenhead, UK, Gaelle Dumas and Eva Schinnerer from the Max Planck Institute for Astrophysics in Heidelberg, Germany, and Andreas Zezas, from CfA and the University of Crete in Greece.

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4.2 / 5 (5) Mar 11, 2011
This article get's a 5 automatically just for the Tolkien reference.
5 / 5 (3) Mar 11, 2011
This article get's a 5 automatically just for the Tolkien reference.

I appreciate the influence those books have spread throughout the world and I read them years ago, but I really thought they were rather boring...but this is coming from a person who is a fan of Russian literature...

Cool article and images though.
1.6 / 5 (7) Mar 11, 2011
Or thirdly, the outflow of gas from the central region is a natural consequence of the instability of the massive core star, which seeds the galaxy with newly nucleated matter and energy. It seems quite a challenge to insist that this outflow must result from accretion inflows, especially given recent examples of superwind outflows from core regions, such as in M82. I suspect the feedback happens rather inside the core star itself, often leading first to pulsation, then occassional ejections, resulting in effects such as Fermi bubbles, or less frequently to explosions, such as some supernovaes, or perhaps even more rare gamma-ray bursts.
4.7 / 5 (6) Mar 11, 2011
but I really thought they were rather boring
Skip the damned elves and their bloody stupid singing and the books improve a great deal. Most of the Elves in LOTR are a bunch of whiny wankers.

'Well we could kick Sauron's ass but we can't be bothered. We have to piss off to the West Real Soon Now. Here have this young twit of a bowelf to take with you. He is a pain in the ass so if you get him killed its no skin off our in the air noses. Have some Hardtack which we have renamed something suitably pretentious. Have some weapons we conned from the dwarves. Now go away and don't bother us again.

There's a song too.

Oh Tuxford is a Crank
He Cranks on and on
He believes in magic
And he is fond of elves
Elves cause brain damage
So we circle round

Oh Tuxford is a Crank

Repeat ad infinitum like Tux and Oliver

not rated yet Mar 11, 2011
^ I laughed out loud. No, really -- it was audible laughter.
not rated yet Mar 12, 2011
It looks like a galaxy gone wrong. Where is all the stars?
4.7 / 5 (6) Mar 12, 2011
"It looks like a galaxy gone wrong. Where is all the stars?"

This study of NGC 4151 is looking at a very small, 3000 parsec-wide region near the galaxy's nucleus:

Radio observations(red) show a large circumnuclear ring of hydrogen, which is commonly seen near the nuclei of barred spiral galaxies(of which NGC 4151 is a member).

The visual light observations(yellow) are actually a combination of two images of the nucleus taken by HST (V & H-band) and are degraded in resolution to match that of the radio & x-ray observations.

The yellowish blobs are massive, starforming H II regions embedded in the hydrogen ring.

Hope that helps a bit.

5 / 5 (6) Mar 12, 2011
"....commonly seen near the nuclei of barred spiral galaxies(of which NGC 4151 is a member)"

I misspoke here. NGC 4151 is a spiral galaxy of type (R')SAB(rs)ab [from NED, paper].

This galaxy has been well studied in part because of its brightness and relative distance. It was one of the original galaxies studied by Carl Seyfert back in 1943, and are commonly known today as Seyfert galaxies: http://en.wikiped...t_galaxy
1 / 5 (8) Mar 13, 2011
Or thirdly, the outflow of gas from the central region is a natural consequence of the instability of the massive core star, which seeds the galaxy with newly nucleated matter and energy.

Yes, Tuxford, potential energy (E) against repulsive forces is stored as rest mass (m) in tiny, massive centers of atoms, stars and galaxies.

[1] "Neutron Repulsion," The APEIRON Journal, in press (2011), 19 pages

[2] Video on neutron repulsion:

Hang in there!
Oliver K. Manuel
Mar 14, 2011
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