Sky & Telescope - April 2019 - 55

SUE FRENCH (3)

encounter with M81 a few hundred
million years ago. The tidal effects triggered a tremendous burst of star formation in M82, stars whose ﬁerce stellar
winds and supernova explosions are
ﬂinging gas and dust out of the galaxy.
The slow dance of future encounters
may ultimately merge the pair into a
single galaxy in the remote future.
Now that we've seen our pair, let's
go for three of a kind in the guise of
the Leo Triplet, composed of Messier
65, Messier 66, and NGC 3628. The
trio is pretty even at 23×, sitting 1°
east of 73 Leonis. M65 and M66 appear
bright, and NGC 3628 is nicely visible
as an elongated streak. As shown in
my sketch with a wide-angle eyepiece
giving 102×, the galaxies are most
fetching when sharing the ﬁeld of view,
but they surrender more detail when
examined individually at 164×. M66's
core tips north-northwest, holding a
bright elongated center. Delicate hints
of spiral arms sprout from each end of
the core, unwrapping counterclockwise
in my mirror-reversed view. M65 bares
a roundish core with a small brighter
center. The brightest area of NGC 3628
stretches across 7′, while fainter tips
that are best seen with averted vision
extend the length to 11′.
Gravitational interactions have left
their mark on the Triplet. M66 boasts
spiral arms that twist above the galaxy's
disk and an offset core. Even more
mussed, NGC 3628 has oddly ﬂared
ends as well as a tidal tail of gas and
stars extending roughly a half million
light-years. The tail's tip is punctuated
by Leo-TDG, thought to be a tidal dwarf
galaxy formed from the tail's debris.
The Whirlpool Galaxy, NGC 5194, in
Canes Venatici is one of the best targets
in which to seek out spiral structure.
As a bonus, its interacting companion
NGC 5195 enhances the scene. Together
they're known as Messier 51. These
galaxies are an easy catch at 23×, each
one sporting a relatively large core. At
164× a bright nucleus dwells at the heart
of each galaxy. NGC 5194's arms can be
traced fairly well, but not with the detail
afforded by larger scopes. One of the
arms reaches out toward its companion,

yet remains beyond its grasp. Images
seem to show the Whirlpool's northern
spiral arm latched onto its companion,
but this is an illusion. NGC 5195 is
tumbling by its larger neighbor, and we
merely see the arm superimposed on the
receding companion. The Whirlpool's
pronounced, two-armed spiral structure
may have been induced by the gravitational effects of an earlier encounter.
Way over on the opposite end of the
Big Bear from M81 and M82, Messier
101 is an intriguing galaxy for a small
telescope. At 23× its large, diaphanous
glow brightens only slightly toward the
center. On a good night, a magniﬁcation of 164× coaxes out three spiral
arms. A 13th-magnitude star sits 1.3′
north-northeast of the small nucleus.
At low magniﬁcation the galaxy spans
roughly ¼°, but the outer reaches seem
to fade away at 164×, so my sketch on
the next page only covers the central
9′ of the galaxy. On very good nights,
better than the two I had for this
sketch, I've been able to nab a few of
the brightest star-forming regions in
M101's outlying arms, notably NGC
5471, NGC 5462, NGC 5461, and the
combined glow of NGC 5447 and NGC
5450. In addition to favorable skies, it
takes patience and the judicious use of
averted vision to hunt these down. If
you'd like to tackle the project, you'll
ﬁnd a labeled chart to help you on
S&T's website (skyandtelescope.com).
Just enter "Guide to Messier 101" in
the search box.
Let's end our tour with NGC 5907
in Draco, a lovely example of a ﬂat
galaxy - a disk-shaped galaxy that's
seen edge-on from our vantage point
on Earth and has little or no central
bulge. I ﬁnd these celestial toothpicks
of light quite appealing. Although fairly
faint, the slender glow of NGC 5907
can be seen tipped north-northwest at
37×. Examining it at 102×, I can follow
its length for about 8′, shining faintly
at the tips and growing softly brighter
toward the center. Folks with 8-inch
or larger scopes should look for this
remarkable galaxy's dust lane.
Deep images of NGC 5907 are spectacular. Magniﬁcent loops of stellar

M81

M82

NGC 3628

M65
M66
WN

p Top: Increase the magnification to reveal
more of M81's structure. A brighter core is
readily apparent, but the delicate spiral arms
take more study. This sketch shows the author's view of M81 at 164×. All sketches shown
here were made with a 130-mm refractor.
Middle: At 164×, M82's mottled appearance
becomes more visible. Look for the dark dust
lanes interrupting its brighter areas, particularly
on the galaxy's south edge. Bottom: Use a
wide-angle eyepiece and lower magnifications
(the scene here was captured at 102×) to keep
the trio of M65, M66, and NGC 3628 in the
same field of view.
sk yandtele scope.com * A PR I L 2 019

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Sky & Telescope - April 2019

Table of Contents for the Digital Edition of Sky & Telescope - April 2019