Astronomy

(Ann) #1
BINOCULARUNIVERSE
BY PHIL HARRINGTON

68 ASTRONOMY • APRIL 2018

W


ith the Milky
Way ’s c u r t a i ns
of cosmic dust
drawn away,
the spring sky
window opens toward the deep-
est recesses of the universe. The
view offers us an unparalleled
opportunity to explore the
depths of intergalactic space.
Commanding center stage in
the April sky is Leo the Lion.
Within its boundaries are sev-
eral galaxies bright enough to
see through binoculars, albeit
with some effort.
The two brightest are M65
and M66. They appear just 20'
apart, to the southeast of the
star Theta (θ) Leonis. Theta
marks the right angle in the
triangle of stars forming Leo’s
back and tail.
Charles Messier discovered
M65 and M66 on March 1,


  1. Seven years earlier, on
    November 1, 1773, a comet he
    had discovered passed between
    these two galaxies. Messier’s
    records show he was viewing
    his comet that evening, but he
    “did not see [the galaxies],
    without doubt due to the light
    of the comet.”


To find this galactic pair,
drop 2.5° (or about half a bin-
ocular field) south of Theta
Leonis to 5th-magnitude 73
Leonis. From there, glance very
carefully about half a field to
the left (east-southeast). Can
you spot a dim smudge of light
there, just south of a faint star?
If so, congratulations — you
just found M66.
Messier’s notes describe M66
as “very weak.” True, it is faint,
but it is certainly well within
the grasp of most binoculars.
My notes made through 10x50
binoculars recall it as an “oval
nebulous disk highlighted by a
brighter central core, which
appears stellar.”
M66 is classified as a type Sb
spiral, with two arms curving
away from the galactic nucleus.
The western arm appears dis-
tended, probably due to a game
of gravitational tug-of-war
waged with a neighboring gal-
axy. There appears to be a large
amount of cosmic dust and
reddish nebulae scattered
throughout M66’s spiral halo,
both signs of extensive star-
formation regions triggered by
intergalactic tidal forces.

When you spot M66, you
may also notice a dimmer oval
smudge of light just to its west.
That’s type Sa spiral M65,
which shows tightly wound
spiral arms in photographs. The
arms appear uniform and
neatly arranged, leading astron-
omers to conclude that M65 is
not the cause of M66’s dishev-
eled appearance.
M65 is about half a magni-
tude fainter than M66, and
therefore more challenging. If
you have trouble, try support-
ing your binoculars on a tripod,
fence post, or by some other
means to steady the view. Like
M66, M65 presents an oval disk
surrounding a starlike core.
Although they appear about the
same length, M65 looks thinner
because of its slightly narrower
tilt from our perspective.
I can see M66 through my
10x50s from my suburban back-
yard fairly routinely, but M65
takes a better-than-average
night. Under superior condi-
tions, however, I’ve spotted both
through braced 7x35 binoculars.
Looking at charts of the area,
you’ll notice a third galaxy just
north of M65 and M66. That’s
NGC 3628. This Sc spiral has
the loosest spiral structure of
the three. From our vantage
point, we see this distant island
universe almost exactly edge-
on. Telescopes show the galaxy’s
edge is girdled by a conspicuous
band of dark dust clouds, which
effectively obscure the bright
central region and hide most of
the young stars in the spiral
arms.
Try as I might, I’ve never been

able to see NGC 3628 through
my 10x50s. It also gives my
16x70s a run for their money.
Only when piloting my 25x100s
can I make out a faint smudge
of grayish light just north of the
other two. It’s a toughie.
Let’s wrap up our survey this
month by visiting a fun bin-
ocular asterism. Follow a zigzag
line south of Theta Leonis, past
the stars Iota (ι) and Sigma (σ)
Leonis, to a small four-star arc
that hooks to the southeast.
The brightest star in the arc,
4th-magnitude Tau (τ) Leonis,
teams with a fainter point to its
southeast to create a pretty
double star through binoculars.
There’s more: By shifting Tau
toward the upper right (north-
west) corner of your field, you
should spot not one, not two,
but three more faint doubles.
All four pairs collectively fall
into an X pattern. Add them
together, and you get an aster-
ism that I like to call the
Double Cross. None of the
four pairs is a true physical
binary since all eight stars are
at very different distances, but
that doesn’t detract from their
unique appearance through our
binoculars.
We all have favorite binocu-
lar objects. I’d enjoy hearing
about yours — contact
me through my website,
philharrington.net.
And always remember that
two eyes are better than one.

The Leo Trio


plus one


Splendid galaxies await
you in the Lion.

Highly inclined spiral M65 is one of the more beautiful galaxies in the springtime sky.

The edge-on galaxy NGC 3628 sports a
dust lane running along its bright disk.
KEN CRAWFORD

Spiral galaxy M66 has a beautiful disk
intertwined with dust lanes and pinkish
star-forming regions. ADAM BLOCK/MOUNT
LEMMON SKYCENTER/UNIVERSITY OF ARIZONA

Phil Harrington is a longtime
contributor to Astronomy and
the author of many books.

ADAM BLOCK/MOUNT LEMMON SKYCENTER/UNIVERSITY OF ARIZONA
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