66 ASTRONOMY • MAY 2020BINOCULAR UNIVERSE
One of the first catchphrases we probably all
heard when learning our way around the
spring sky was that from the handle of the Big
Dipper, you “arc to Arcturus, then speed to Spica, and,
finally, curve to Corvus.” Arcturus and Spica are bril-
liant stellar beacons, far outshining the handle stars
that guide us their way. The four primary stars that
make up the trapezoidal body of Corvus the Crow,
however, shine at an insipid 3rd magnitude. Despite
their modest numbers, those four stars stand out sur-
prisingly well, even under the veil of subur-
ban light pollution.
Let’s begin our exploration at Zeta (ζ)
Corvi, a wide double star within the southern
confines of the trapezoid. Shining at 5th
magnitude, Zeta shows a subtle hint of blue,
while its 6th-magnitude companion,
HD 107295, 6' to the west, is yellowish.
Whether they form an actual binary star
s y stem or ju st a cha nc e opt ic a l double i s open
to debate. Zeta is projected to be 415 light-
years away, while HD 107295 is calculated at
386 light-years distant. Some ambiguity in
the data, however, may mean that they are actually
much closer to one another.
Corvus also holds a second widely spaced double
star about 2° south of the midway point between Beta
(β) and Epsilon (ε) Corvi. The brighter of the pair is
6th-magnitude 6 Corvi, while 5' to its west is
HD 107756, one magnitude fainter. Both are orange
giant stars. Slightly defocus your binoculars to
enhance their delicate colors.
By extending an imaginary line from Delta (δ)
through Beta Corvi along the trapezoid’s western side,and continuing southward for 3½°, you will come to
5th-magnitude HD 109799 in neighboring Hydra. Can
you also see a smudge of faint light just to its northeast?
That will be M68, a rogue globular cluster lying in the
Milky Way’s outer halo, about 33,600 light-years from
us. Owing to its southern position in the sky from
midnorthern latitudes, M68’s gentle glow can be
quickly extinguished by horizon-hugging light pollu-
tion and haze. But if you wait for a moonless night, it
will reveal itself with just about any binocular. As you
st r a i n to se e M6 8 , consider t hat t hat fe eble g low i s ac t u-
a l ly t he combi ned ef for t of more t ha n 10 0, 0 0 0 st a rs t hat
have been in existence for an estimated 11 billion years.
The long-period variable star R Corvi lies within the
trapezoid, about 2½° southeast of Gienah (Gamma [γ]
Corvi). Like most long-period variables, R Corvi is a red
giant that varies dramatically from maximum to mini-
mum. At peak brightness, it reaches magnitude 6.7, while
at minimum it drops to magnitude 14.4. A full cycle,
from one max to the next, takes approximately 317 days.
And, guess what? It’s on the rise. Max light is predicted
to occur in mid-June, so now is a great time to check it
out. It forms a tiny right triangle with two faint stars that
it w i l l e a si ly out sh i ne a s it a sc end s. Use t he c u stom i z able
Variable Star Plotter on the American Association of
Variable Star Observers’ website, http://www.aavso.org, to
create your own f inder chart.
Just north of Gamma Corvi, there is an arrow-shaped
asterism of eight 6th- and 7th-magnitude stars that
points right at our next target, the Sombrero Galaxy
(M10 4). W hat cou ld be more conven ient t ha n t hat? T he
ga la x y i s ju st 2 ° nor t he a st be yond t he a r row ’s
tip, barely across the invisible boundary in
Virgo. Although M104 shines at only 9th
magnitude, my old 7x35s still reveal its oval
disk. Increasing to my 10x50s, that disk
grows more prominent, surrounding a stellar
core. It takes my 16x70s to reveal why M104
is nicknamed the Sombrero; they reveal a
protruding core and broad, f lattened disk
cleaved by a “brim” of opaque dust.
Finally, look about halfway between the
tip of the arrow and M104. Can you see a tiny
triangle of faint stars? If you are viewing
through 14x or higher giant binoculars, you might
notice that there are six stars here, forming a triangle
within a triangle. Nicknamed the Stargate, this little
object is one of my favorite spring time asterisms.
I always enjoy hearing of your binocular exploits and
successes. You can contact me through my website,
philharrington.net. Until next time, remember that two
eyes are better than one.The region of the crow hides some pretty cool celestial stuff.
Curve to Corvus
and beyond
The magnificent
Sombrero Galaxy
(M104) is a great
edge-on spiral, and
makes a fine target
for any pair of
binoculars. R. JAY GABANYI always
enjoy
hearing
of your
binocular
exploits and
successes.BY PHIL
HARRINGTON
Phil is a longtime
contributor to
Astronomy and the
author of many books.BROWSE THE “BINOCULAR UNIVERSE” ARCHIVE AT
http://www.Astronomy.com/Harrington