36 M86
M86 is a 9th-magnitude elliptical/lenticular galaxy at the core of the
Virgo Cluster, lying only 17' from M84 (see #35). Messier discovered it
together with M84, saying the two “nebulae” had the same appearance.
On the surface, they do. With its smooth-looking face, M86, like M84, gets
gradually fainter the farther you look away from the core. And at a glance,
M86 may appear only slightly larger than M84 through a small telescope.
But this is an illusion created by the galaxy’s lower surface brightness.
M86 is, in fact, twice the apparent diameter of M84 and is slightly more
elliptical. M86’s 400 billion stars span a whopping 135,000 light-years.
Aside from its sharp nucleus in a diffuse core, M86 is a visual “softy” —
a porcelain-pure oval of diffuse light. Studies of M86’s core have revealed
a slight dimming, which could suggest the core is surrounded by a dust
ring or torus, though other studies have contested this.
M86 is tidally interacting with NGC 4438 (about 25' to the east-
northeast), and a nearly 400,000-light-year-long Hydrogen-alpha
filament clearly connects them. While M86 does not have an apparent
outer envelope, it does harbor some 3,800 globular clusters. It doesn’t
seem to be interacting with its tiny companion NGC 4402, located about
10' north of its core, though its halo has several streamers, suggesting it
has consumed some of its other neighbors in the past.
While the majority of the Virgo Cluster is receding from the Milky Way,
M86 is moving closer to our Milky Way Galaxy at 940,000 mph (1.5 mil-
lion km/h). This is a consequence of M86’s orbit around the Virgo Cluster:
The galaxy is currently on the far side of the cluster relative to us, and
moving toward the cluster’s center. — S.J.O.35 M84
M84 is a member of a dynamic pairing with M86 (see #36). A round giant
elliptical galaxy some 80,000 light-years wide, M84 shines across 55 million
light-years of space. It resides in the Virgo Cluster of galaxies, the near-
est of the large extragalactic populations. This, of course, was unknown to
Charles Messier when he discovered it on March 18, 1781, noting that its
“center is pretty bright, surrounded by slight nebulosity.” Little has changed
in astronomers’ descriptions of the object to this day.
Elliptical galaxies are one of three main classes of galaxies defined by
American astronomer Edwin Hubble in 1936. They have no discernible struc-
ture except for their ellip-
soidal shape. Nevertheless,
they are among the most
abundant type of galaxies in
the universe and are usually
found near the cores of
galaxy clusters.
M84 is one of the more
prominent ellipticals near
the center of the Virgo
Cluster. It has a compact
nucleus and two warped
dust lanes perpendicular to
a radio jet that streams from
the core in a north-south
direction. This gas disk
surrounds a black hole with
a mass of about 1.5 billion
Suns. M84’s outer halo
appears smooth, dotted
with prominent globular
clusters. Its stars appear to be very old, dating back nearly 12 billion years.
To find this 10th-magnitude galaxy, look about 5° northwest of Rho (ρ)
Virginis. Through small- to moderate-sized telescopes, the galaxy appears
as a 5' glow, slightly out of round with a stellar nucleus surrounded by a
tightly packed core. In images, the core’s intensity is slightly enhanced by
a superimposed 14th-magnitude star.
M84 is visually part of Markarian’s Chain, a string of eight galaxies that
form a 1.5°-long line that shines like flying paper lanterns at the core of the
Virgo Cluster. Armenian astrophysicist Benjamin Markarian discovered this
feature in the 1960s, noting that these galaxies share a common motion
though space. However, later observations have shown that M84 is not
a dynamical member of the chain, as its motion does not jive with the
rest. — S.J.O.
GREG MORGAN24 ASTRONOMY • JANUARY 2022
37 M87
M87 is yet another Messier elliptical galaxy in the
Virgo Cluster, 55 million light-years distant and
some 120,000 light-years across. It lies about 3½°
northwest of Rho Virginis. But M87 outdoes M84
(see #35) and M86 (see #36) in sheer mass: It has
least a trillion stars totaling a mass of 2.7 trillion
Suns. That makes it one of largest, most massive,
and most luminous galaxies in our local universe.
Charles Messier discovered M87 on March 18,
1781 — the same night he found M84 and M86 —
and one can only wonder what went through his
mind as he spotted these three cometlike objects
in the same area of sky. At magnitude 8.6, M87 is
slightly brighter than the other two and in between
them in size.
M87 is most likely the visible remains of an
extragalactic merger between two galaxies. This
combined cosmic powerhouse now features a
furious jet of matter blasting out from its nucleus.
Heber Curtis at Lick Observatory first noticed
this “curious straight ray” in 1918 on photographic
plates. The jet is a very strong central radio
source and is powered by a 6.5-billion-solar-
mass black hole — one of the largest known. In
2017, astronomers used an international network
of radio telescopes called the Event Horizon
Telescope to zoom in on the heart of M87 and
capture the first image of a black hole and its
shadow, which was released in April 2019.
The first visual observation of M87’s
5,000-light-year-long jet was made by Otto
Struve through the 100-inch telescope at Mount
Wilson. It was thought to be beyond the grasp
of amateur astronomers until the late Barbara
Wilson first sighted it through her 20-inch
reflector during the 1991 Texas Star Party.
Otherwise, the galaxy is quite typical for an
elliptical. Namely, it resembles an unresolved
globular cluster or the head of a comet just
beginning to shine — one with a bright spheri-
cal shell that gradually condenses inward. A
dimmer elliptical, 11th-magnitude NGC 4478, lies
only 10' southwest of M87; it requires modest to
high magnifications to see well. — S.J.O.GREG MORGANADAM BLOCK/NOAO/AURA/NSF