[梅西耶天体观测指南]-Stoyan_Atlas_of_the_Messier_Objects_2008_部分5.pdf

M 87 is the most massive and
largest object in the Messier catalog
and the central galaxy of the Virgo
cluster. Bernd Flach-Wilken.
M 87. A jet, in which particles nearly reach
the speed of light, is ejected by the galaxy
core. Hubble Space Telescope.
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Recent observations have shown that recurrent out-
bursts continually change the observed jet struc-
tures. In 2003, a newly formed knot, only " from
the nucleus, was even brighter than the latter in vi-
sual light. The jet outfl ow is relativistic, and appa-
rent velocities beyond the speed of light have been
observed, caused by projection effects.
The jet originates from a central region only 60
light-years wide, but which contains a mass of 2 to
3 thousand million solar masses. An accretion disk
surrounds, we may safely assume, a super-massive
black hole. Tsvetanov et al. have registered bright-
ness variations of about a factor of 2 within two
and a half months, from the innermost region of 16
light-years diameter. Apart from these variations,
there are other characteristics of the nucleus of M 87
which coincide well with those of BL Lacertae ob-
jects (see M 77) and LINER-type galaxy cores, inclu-
ding the relativistic jet. Atypical, however, is the re-
latively faint nucleus of M 87. That may be the result
of the inclination of the M 87 core region by 30° to
35° from our line of sight, causing obstruction, while
BL-Lac objects are seen fully face-on.
Furthermore, the nucleus of M 87 is one of the
most luminous radio sources in our sky (Virgo A),
which was discovered in 1954 by Baade and Min-
kowsky. Owen and colleagues (1999) discovered a
radio halo around M 87 that spans 200,000 light-
years and is heated by the jet. And we know that
M 87 is a prominent X-ray source as well.
The single supernova observed so far in M 87
occurred in February 1919. It was only discovered
three years later, by Balanowsky, on photog