Image 1 Caption: M87 (NGC 4486) in the Virgo Cluster (near the center of mass???) in constellation Virgo.
M87 is cD or giant elliptical galaxy with relativistic jet that expands into the lobe (77 kpc in length) seen in Image 1.
Image 1 is a collage of true-color visible light and, to emphasize the jet-produced lobe, some other electromagnetic radiation (EMR) from some other electromagnetic spectrum band maybe ultraviolet or radio---or so believes yours truly---the original caption did NOT fully elucidate. The lobe is visible in visible light, but NOT prominently---or so believes yours truly. See Hubblesite: Black Hole-Powered Jet of Electrons and Sub-Atomic Particles Streams From Center of Galaxy M87 for some elucidation.
Features:
For comparison, note that the Andromeda galaxy (M31, NGC 224) (the closest non-dwarf galaxy) is at 0.778(17) Mpc = 2.54(11) Mly.
Note the value 0.004360(22) << 0.5, and so M87 is well inside the local universe.
However, the galactic halo has radius of maybe 150 kpc or more. It is always hard to tell how far the gravitational well (essentially the total galactic halo) of galaxy extends (particularly in dark matter) since you run out of tracers: e.g., very bright stars and globular clusters.
The Milky Way has 150 known globular clusters with maybe 10 to 20 more to be discovered (see Wikipedia: Globular cluster)
The lobe extends to out to 77 kpc.
The relativistic jet is plasma gas with the cosmic composition with metallicity somewhat uncertain???.
The relativistic jet originates in and is perpendicular to an accretion disk orbiting the M87* (see M87 Supermassive Black Hole First Image below).
There is evidence for a counter relativistic jet in the opposite direction, but it is hard detect (see Wikipedia: M87: Jet).
We have dicussed in the preamble the probable collage nature of Image 1.
Image 2 Caption: Behold the black hole: M87 supermassive black hole (M87*)---which is near the center of mass of giant elliptical M87 (see Wikipedia: M87: Supermassive black hole (M87*)). This is M87 Supermassive Black Hole First Image: announcement 2019 Apr10.
Features:
EHT has also imaged the Galactic center black hole called Sagittarius A* (Sgr A*). That image will be released in the future (see Time Magazine, 2019 Apr10).
In fact, for an isolated black hole you do NOT see the event horizon, but rather you see the black hole shadow---the region from which light CANNOT reach the distant observer. For an explication of black hole shadow, see Black hole file: black_hole_shadow.html. Since M87* is a Kerr black hole (a non-ideal one), it would have slightly different formula for its black hole shadow than that of a Schwarzschild black holes.
The emission from the accretion disk surrounding M87* partially fills in its black hole shadow in a complicated way.
The confirmation that we are seeing a black hole surrounded by an accretion disk is the fact that Image 2 matches computer simulations of what the M87* should look like. Thus, Image 2 confirms to near-certainty the existence of the event horizon which is the defining characteristic of black holes, but it is NOT a simple direct confirmation.
Note also that the accretion disk probably has temperature of order a few times 10**6 K, and so probably radiates much more strongly in the X-ray band (fiducial range 0.1--100 Å) (see wien_law.html) than in the radio band 0.1 cm -- 10**5 km, but we can only resolve M87* in the radio band.
The Schwarzschild radius formula applies to non-rotating black holes and one should use the formula for the Kerr-Schwarzschild radius for rotating black holes since the M87* is rotating. However, for crude estimates the Schwarzschild radius formula is probably adequate.
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