Above: The 12th-magnitude galaxy NGC 2964
(top right) lies near another strange galaxy,
NGC 2968, which has a twisting dark lane
running across its midsection. JOHN BESWETHERICK/
ADAM BLOCK/NOAO/AURA/NSF
Left: Another trio in Leo consists of M95 (left),
M96 (above center), and the elliptical galaxy
M105 (right). Other galaxies lie near M105,
including NGC 3384 (above and right of M105)
and NGC 3389 (above NGC 3384). DANIEL B. PHILLIPS
NGC 3628 has a tail
that looks like an
ocean liner trailing
smoke. Can it be
seen visually? And if
so, at what aperture
and magnification?
make a 10˚ sweep east with a wide-field
eyepiece. You are within striking range of
another celebrated pack of reasonably
bright galaxies: M95, M96, and M105.
M95 and M96 are separated (east-west)
by only 42'; both magnitude 9.5 barred spi-
rals are about 7' wide, with tight arms that
wind around a bright core, forming both a
bright inner annulus and a fainter outer
ring. Only M95 is seen nearly face-on
(looking like the Death Star from Star
Wars), while M96 is inclined 45˚. M96 is
also the more curious of the two, as it is a
one-armed spiral that loops around the
core from the southwest to perform a tight
counterclockwise inner swirl, forming an
ill-defined inner annulus before looping
again to form a warped outer loop, the
northern rim of which is rife with star
formation. And this is where it gets
interesting.
About 1˚ east-northeast of M96 lies its
extragalactic neighbor M105, with two
close attendants: the 11th-magnitude len-
ticular galaxy NGC 3384 about 7' to the
northeast and 12th-magnitude NGC 3389
(which is most likely a background galaxy)
near equidistant to the southwest. We can
now imagine the location of the Leo Ring,
a giant blossom of cold gas that surrounds
these galaxies; it once was one of the night
sky’s most dramatic and mysterious clouds
of intergalactic gas in the radio spectrum.
First detected by radio telescopes in
1983, the ring was further studied in 2009
by the ultraviolet vision of NASA’s GALEX,
which detected emissions interpreted as
dwarf galaxies forming out of primordial
gas. A year later, astronomers using the
Canada-France-Hawaii Telescope found
optical emissions associated with the ring
— not from dwarf galaxies, but from bursts
of star formation along the ring. Their
models indicate that the gas is not primor-
dial, but formed by a billion-year-old colli-
sion between M96 and NGC 3384.
Let’s slip far to the northwest corner of
Leo’s boundaries, about 5˚ southeast of
Alpha Lyncis, where we’ll find the “other”
Leo Triplet: 12th-magnitude NGC 2964,
13th-magnitude NGC 2968, and 14th-
magnitude NGC 2970. Included in
Astronomy contributing editor Phil
Harrington’s Cosmic Challenge, this triad
appears through modest-sized telescopes as
a series of extragalactic “dust motes.”
Whereas NGC 2964 is oriented east-
west, measures 3' by 1.5' across, and sports
a tiny, fuzzy core, NGC 2968 is oriented
northeast-southwest, measures 2' by 1.5',
and reveals no core. In reality, NGC 2964 is
a mixed spiral galaxy, and NGC 2968 is an
irregular galaxy with a peculiar S-shaped
dust lane running lengthwise through its
body. But there’s more! A tidal tail con-
nects NGC 2968 and NGC 2970, extending
to the northeast. NGC 2970 is a true visual
dust mote, measuring only 0.5'.
NGC 2968 is very distorted and sur-
rounded by shells. What’s more, a super-
nova occurred in 1970 on the luminous
bridge, confirming a physical association
between NGC 2968 and NGC 2970.
If you make an astonishing observation
of any of these exotic features, send an
email to [email protected].
Stephen James O’Meara is a well-known
observer, author of many books, and a
contributing editor of Astronomy.
W W W.ASTR ONOMY.COM
57