Thursday, August 22, 2013

Space Slinky Discovered By Astronomers

Astronomers have assembled, from more than 13 years of observations from NASA's Hubble Space Telescope, a series of time-lapse movies showing a jet of superheated gas -- 5,000 light-years long -- as it is ejected from a supermassive black hole.


The movies promise to give astronomers a better understanding of how black holes shape galaxy evolution.

"Central, supermassive black holes are a key component in all big galaxies," said Eileen T. Meyer of the Space Telescope Science Institute in Baltimore, Md. "Most of these black holes are believed to have gone through an active phase, and black-hole powered jets from this active phase play a key role in the evolution of galaxies. By studying the details of this process in the nearest galaxy with an optical jet, we can hope to learn more about galaxy formation and black hole physics in general."

The research team spent eight months analyzing 400 observations from Hubble's Wide Field Planetary Camera 2 and Advanced Camera for Surveys. The observations, taken from 1995 to 2008, are of a black hole sitting in the center of a giant galaxy dubbed M87.

This video begins with a view of the stars and galaxies in the spring constellation Virgo. We zoom into the giant elliptical galaxy M87, which lies near the center of the Virgo cluster of galaxies. A high-speed jet of hot plasma is buried deep inside the galaxy. A supermassive black hole ejects the jet at nearly the speed of light. This Hubble Space Telescope time-lapse movie captures the movement of the jet over a timespan of 13 years.

Credit: NASA, ESA, and G. Bacon (STScI)

"We analyzed several years' worth of Hubble data of a relatively nearby spiraling jet of plasma emitted from a black hole, which allowed us to see lots of details," Meyer said. "The only reason you see the distant jet in motion is because it is traveling very fast."

Meyer found evidence that suggests the jet's spiral motion is created by a helix-shaped magnetic field surrounding the black hole. In the outer part of the M87 jet, for example, one bright gas clump, called knot B, appears to zigzag, as if it were moving along a spiral path. Several other gas clumps along the jet also appear to loop around an invisible structure.

M87 resides at the center of the neighboring Virgo cluster of roughly 2,000 galaxies, located 50 million light years away. The galaxy's monster black hole is several billion times more massive than our sun.

The Hubble data also provided information on why the M87 jet is composed of a long string of gas blobs, which appear to brighten and dim over time.

"The jet structure is very clumpy. Is this a ballistic effect, like cannonballs fired sequentially from a cannon?" Meyer asked, "or, are there some particularly interesting physics going on, such as a shock that is magnetically driven?"

Meyer's team found evidence for both scenarios. "We found things that move quickly," Meyer said. "We found things that move slowly. And, we found things that are stationary. This study shows us that the clumps are very dynamic sources."

It is too soon to tell whether all black-hole-powered jets behave like the one in M87, which is why Meyer plans to use Hubble to study three more jets. "It's always dangerous to have exactly one example because it could be a strange outlier," Meyer said. "The M87 black hole is justification for looking at more jets."

The team's results appeared Aug. 22 in the online issue of The Astrophysical Journal Letters.

For images and more information about M87's jet, visit:
http://www.nasa.gov/hubble  and http://hubblesite.org/news/2013/32

1 comment:

  1. Comment copied from the Computational Astronomy Blog Site;

    Hurrah! - Some fearless scientific honesty at last (I tracked down the ApJ paper itself), having the courage to openly confirm findings of 0.45c wrt the nearby LOCAL background ('Proper motion') frame of the M87 galaxy, and even in the abstract (see below).

    Now we wait for any backlash from the well meaning but intellectually challenged nay sayers. Or perhaps enough have now followed Max Planck's advice and died off!

    As Einstein wrote pointedly in 1952; "The Special Theory of Relativity is entirely contained within the postulates". This is the experimental proof, also confirming 'Local Reality' (plus gamma). A note to forestall straw grabbing; The Rees-Sciama effect (not mentioned) is quite valid but has a limited magnitude and angular domain, not able to explain the consistent 'apparent' speeds in the HST frame of often over 10c.

    Abstract.
    "We report new results from an HST archival program to study proper motions in the optical jet of the nearby radio galaxy M87. Using over 13 years of archival imaging, we reach accuracies below 0.1c in measuring the apparent velocities of individual knots in the jet. We confirm previous findings of speeds up to 4.5c in the inner 6" of the jet, and report new speeds for optical components in the outer part of the jet. We find evidence of significant motion transverse to the jet axis on the order of 0.6c in the inner jet features, and superluminal velocities parallel and transverse to the jet in the outer knot components, with an apparent ordering of velocity vectors possibly consistent with a helical jet pattern. Previous results suggested a global deceleration over the length of the jet in the form of decreasing maximum speeds of knot components from HST-1 outward, but our results suggest that superluminal speeds persist out to knot C, with large differentials in very nearby features all along the jet. We find significant apparent accelerations in directions parallel and transverse to the jet axis, along with evidence for stationary features in knots D, E, and I. These results are expected to place important constraints on detailed models of kpc-scale relativistic jets."

    For the record, I suggest the significant helicity now discovered may not be so much 'produced by' an em field' in the jet structure itself but can be logically derived from precession at the axis of the (two!) contra-flow jets, as predicted in 2010 here; 'Helical CMBR Asymmetry...;' http://vixra.org/abs/1102.0016 The speeds in the ApJ paper are noted as effectively 'collimated' with an outer layer track found at ~0.6c.

    It's then not advisable to take the misguided artists impression in the Scitech version link below the slightest bit seriously.
    http://scitechdaily.com/5000-light-year-long-jet-of-superheated-gas-ejected-from-a-supermassive-black-hole/

    The preprint link to the ApJ paper is here; http://arxiv.org/abs/1308.4633

    Peter Jackson

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