M87 jet formation region |
 | Minimum credit line: Image courtesy of NRAO/AUI
(for details, see .
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M87 is a giant elliptical near the center of the Virgo cluster of
galaxies, nearly 50 million light-years away. At the center of the
elliptical galaxy lies a super-massive black hole, weighing three
billion times more than the Sun. Material being drawn inward by the strong
gravitation of the black hole is formed into a rapidly-spinning flat
disk, called an accretion disk. The subatomic particles are thought to
be pushed outward from the poles of this disk. The scientists believe
that magnetic fields in the disk are twisted tightly as the disk spins
and then channel the electrically-charged particles into a pair of
narrow jets. The charged particles travel at highly relativisitc
speeds as they spiral around the strong magnetic fields which
collimate the jet, and as they do so they emit copious amounts
of radiation at radio wavelengths.
The above image shows views of M87 at different spatial scales. The
bottom image is a 7mm (43GHz) VLBA image of the very central regions of the jet
deep in the heart of the elliptical galaxy. Red (blue) represent
regions of brighter (fainter) radio emission. The white bar indicates
a distance of 0.01 pc (0.0326 light-years), or 2,062 times the
distance from the Earth to the Sun. This image shows that M87's jet
is formed within a few tenths of a light-year of the galaxy's core.
In the formation region, the jet is seen opening widely, at an
angle of about 60 degrees, nearest the black hole, but is squeezed
down to only 6 degrees a few light-years away. The small circle
labeled 6Rs shows six times the Schwarzschild Radius, (radius of the
event horizon) for the galaxy's super-massive black hole. That length
corresponds to slightly more than 9 times the distance from the Sun to
Pluto.
The top two images are from the VLA, and show the radio jet and lobes
at much larger spatial scales. The scales of the images are shown by
white bars in each image: 10 kpc (kiloparsecs) is equal to 32,600
light-years, and 1 kpc equals 3,260 light-years. The top right image
was made from observations at a wavelength of 20cm, and shows
the jets of subatomic particles coming from the core are seen
to balloon into large lobes of radio emission. In the even larger
scale image in the top left, taken at 90cm, the inner lobes are
seen to be smaller features in more extensive radio bubbles,
which extend well outside the elliptical galaxy into the surrounding
intracluster medium.
Investigator(s): W. Junor, J. Biretta, & M. Livio This image is available in the following downloadable versions: If you would like to obtain a higher resolution version of this image,
please contact .
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Telescope
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ALMA
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Date of Observation
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1999-00-00
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Type of Observation
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Continuum Observations
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Band
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Q
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Wavelength
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7 mm
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Frequency
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45 GHz
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Center of Image
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RA: 12:30:49.42, Dec: 12:23:28.00 (J2000)
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Field of View
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0.2500 x 0.2500 degrees
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Technical Caption
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The structures seen at the longer wavelengths
(i.e., 90cm), are larger in part because as the particles travel
outward, they radiate at lower and lower energies, which corresponds
to longer and longer radio wavelengths. As a result, by looking at
longer wavelengths we see radiation from the oldest particles, which
are the ones which travel the greatest dstance.
M87 also is known by radio astronomers as Virgo A, the strongest
emitter of radio waves in the constellation Virgo. The galaxy was
discovered by the French astronomer Charles Messier in 1781. The jet
was first seen in 1918 by Lick Observatory astronomer Heber Curtis,
who described it as "a curious straight ray." The galaxy's radio
emission was first observed by Australian astronomers in 1948/49. M87
is the largest of thousands of galaxies in the Virgo Cluster of
galaxies. The Local Group of galaxies, of which our own Milky Way is a
member, is in the outskirts of the Virgo Cluster.
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