101 SKY OBJECTS
WWW.ASTRONOMY.COM 2129 M104
Dust is a common component of spiral galaxies.
Astronomers believe this dust is carbon- or silicate-
rich and no larger than 0.25 micron wide. It doesn’t
dramatically affect the brightness of galaxies except
in cases where they appear nearly edge-on; then,
their orientation catches the maximum amount of
dust. The Sombrero Galaxy (M104), named for its
resemblance to the famous wide-brimmed Mexican
hat, is easily the brightest edge-on galaxy with a
prominent equatorial dust belt.
It is not exactly edge-on, but at 6° off, it’s very close.
That 6° tilt allows us to see the nuclear region and
makes the asymmetrical starry hub visible above and
below the dark lane. A bright core contains a massive
but quiet black hole with a billion solar masses.
M104 was discovered by Pierre Méchain in- He relayed the information to his observing
partner, Charles Messier, who added it to his list of
non-cometary objects. But the comet observer’s
more detailed thoughts on this and other higher-
number objects in his list weren’t known until
French astronomy-popularizer Camille Flammarion
published Messier’s notes in 1921.
Designated NGC 4594 in John Dreyer’s New
General Catalogue of Nebulae and Clusters of Stars,
this 9th-magnitude galaxy is classified as type Sa,
noted for having a large central hub in relation to
its spiral arms. The arms are tightly wound and lack
large HII regions. With dimensions of 8.7' by 3.5' at
29 million light-years distant, the Sombrero has a
diameter of about 50,000 light-years — half the size
of our home galaxy.
For observers who have never seen a dust belt
in a galaxy, M104 is a great first target because it’s
observable with modest telescopes. Under good
skies, it is within reach of a 6-inch telescope. With
increasing aperture, more detail is visible along the
edge of the dark lane and the bright core becomes
better resolved. Try observing this object with mul-
tiple apertures at a star party.
The Sombrero is easy to find, just 11° due west of
Spica (Alpha [α] Virginis). It’s located in Virgo — but
barely, as it sits slightly north of the border with
Corvus and northeast of Eta (η) Corvi. — A.G.Although galaxies appear
throughout the sky, they are not
spread evenly. They are found in
small groups and larger clusters,
and can be as close as the dwarf
galaxies that orbit the Milky Way
or as far away as the best tele-
scopes can detect.
There is also a swath of sky
where galaxies are few and far
between. Pioneer galaxy observer
Edwin Hubble called this the
Zone of Avoidance. It is so named
because the vast amount of stars,
dust, and gas of the Milky Way’s
plane overwhelm or block the
feeble light of other galaxies.
But while these galaxies’ vis-
ible light is easily absorbed, their
infrared light can penetrate the
dust. Italian astronomer Paolo
Maffei photographed the sky
using a Schmidt camera with
infrared-sensitive film in 1967.
He found two fuzzy patches in
Cassiopeia that became known
as Maffei 1 and 2.Astronomers think that, if not
for its proximity to the galactic
plane (about 0.5° away), Maffei 1
would be among the sky’s bright-
est galaxies. Dust has dimmed this
E3-class elliptical by an estimated
4.7 magnitudes to magnitude 11.1,
although its visible-light surface
brightness — spread over 3.4' by
1.7' — is so low that it appears even
fainter. In infrared light, however,
the galaxy looks much larger. At an
estimated distance of more than
9 million light-years, its long axis is
about 75,000 light-years across.
You’ll find Maffei 1 slightly more
than 4° north-northwest of Eta
(η) Persei and 3° northeast of the
Double Cluster in Perseus (see
#54). But don’t be fooled by the
galaxy’s bright apparent magni-
tude — Maffei 1 is challenging,
requiring a large aperture and
dark skies. It wasn’t until years
after its discovery that this galaxy
was pulled from obscurity, which
is why it isn’t on many observinglists. Look for a faint glow super-
imposed with a sprinkling of faint
foreground stars.
Maffei 1 is the brightest member
of the nearest group behind the
Local Group, along with Maffei 2
and IC 342 — the latter a large,
open-face spiral with a low sur-
face brightness in Camelopardalis.
Among the objects in this
list, Maffei 1 is noteworthy in
two ways: It is one of the most
recently discovered targets and
is among the most challenging
to observe. — A.G.30 Maffei 1
FERNANDO OLIVEIRA DE MENEZES
MATT DIETERICHDAN CROWSON