Sky and Telescope - April 2015 - 57

Sue French

Sue French welcomes your comments at scfrench@nycap.rr.com.

the Owl Nebula. Through 15×45 image-stabilized binoculars, the Owl is fairly easy to see as a little round patch of
mist. M97 and three stars form a pattern that reminds me
of an upside-down Southern Cross (Crux). The nebula
marks the ﬁgure's eastern corner, and the stars shine at
7th and 8th magnitude.
The Owl Nebula is quite evident in my 130-mm scope
at 23×. It appears round and grey, and it has fairly uniform
surface brightness. A 12th-magnitude star perches just
oﬀ its north-northeastern edge. With a bit of attention, the
dusky eyes that give the Owl its name aren't diﬃcult to
discern at 63×; at 91× the nebulosity between the eyes looks
brighter than the sides of the Owl's face. Contrast between
light and dark areas is often exaggerated on my sketches
because I draw them using a dim, red light.
M97's central star has a visual magnitude of 15.8.
Some folks claim that it can be seen with an 8-inch scope,
while others say that a substantially larger telescope is
needed. Let's put that to a test. Try to observe the central
star for yourself, and let me know what size scope and
what magniﬁcation you used, as well as any conditions
that aﬀected your observation. Positive and negative sightings are both welcome. I'll report the results next year
when we can see the Owl again.
Those with large telescopes should try for PGC 34279
(MCG +09-19-014), a little 15.7-magnitude galaxy located
3.8′ south-southeast of M97's center. A 14th-magnitude
star rides on its northeastern ﬂank. The galaxy has been
observed with scopes as small as 14.5 inches in aperture.
Together with M97, PGC 34279 makes an intriguing target for astrophotographers.
For our multiple star, let's visit Zeta (ζ) Ursae Majoris,
better known as Mizar. Its two visual components make
up the ﬁrst physical pair discovered with a telescope. In
1617 Benedetto Castelli, calling Mizar "one of the most
beautiful things in the sky," asked his friend Galileo to
look at it. Galileo's remarks describe an unequal pair
with a 15″ separation. Leos Ondra's fascinating quest for
the story behind Mizar's discovery can be read in full at
http://www.leosondra.cz/en/mizar/.
With good vision and a moderately dark sky, you can
see 4th-magnitude Alcor near Mizar. Observed by Galileo, this pair is within reach of any modern telescope. The
three stars shine nearly pure white in my 105-mm refractor at 47×; they're the brightest stars in the ﬁeld of view.

Each star of the Mizar pair has a close companion
detected by telltale signs in its spectra, making Mizar
a quadruple system. In the March 2010 Astronomical
Journal, Eric E. Mamajek and colleagues announced
the discovery of a red dwarf companion to Alcor. Only
1.1″ from Alcor, the companion was imaged using the
6.5-meter MMT telescope in Arizona. The authors also
employed modern astrometric data to explore the relationship between Mizar and Alcor. They suggest that Mizar
and Alcor form a probable sextuple system, making it the
second-closest sextuplet to us after the Castor system, at 82
and 53 light-years, respectively. Neil Zimmerman and colleagues independently discovered Alcor's companion and
reported it in the February 1, 2010 Astrophysical Journal.
Among the carbon stars, I give my nod to beautiful,
deeply reddish orange Y Canum Venaticorum. In his
1877 book Le Stella, spectroscopy pioneer Father Pietro
Angelo Secchi called this ruddy star "La Superba." He
described it as "Magniﬁcent... truly unique for its vividness. Its color is blood red."

The author sketched M81 and M82 as viewed through
her 130-mm refractor at 63×.
14h

13h

12h

11h

10h

M82

M81

DRACO

+60°

Alcor
Mizar

URSA MAJOR

M97

Star magnitudes

The author's sketch of
M97 as viewed through
her 130-mm refractor
shows how the object
earned the nickname
"Owl Nebula".

2
3
4
5
6

+50°

Sk yandTelescope.com April 2015

http://www.leosondra.cz/en/mizar/ http://www.SkyandTelescope.com

Sky and Telescope - April 2015

Table of Contents for the Digital Edition of Sky and Telescope - April 2015