WWW.ASTRONOMY.COM 57ECULAR CLOUD
down your scope, use magnifications of
120x or greater, and look during deep
astronomical twilight. To my eyes, the
primary shines with a pale aqua hue,
while its dimmer companion is a smoggy
gray. Also check out its roughly 11th-
magnitude companion 34" to the west-
northwest (p.a. 289°). It’s often overlooked
in a quick view and is challenging to see.
Let’s head northward now to catch the
“runaway star” Menkib. With a surface
temperature six times greater than that
of our Sun, this O-type star features
many superlatives. Not only is it one of
the hottest stars visible to the unaided
eyes, but it is also one of the most mas-
sive (weighing in at around 40 solar
masses). It’s also one of the few runaway
stars visible without optical aid, and the
first runaway star to be identified by its
radial velocity alone.Whisking away from us at a velocity
of 37 miles per second (60 km/sec), the
speedy star is now some 16 light-years
from its birthplace at the center of the
Per OB2 Association — roughly midway
between Zeta and Omicron Persei. What
caused Menkib to “run away” was most
likely a massive companion exploding as
a supernova.
On its journey, we see Menkib collid-
ing with a cloud of dense interstellar
matter, itself likely part of an expanding
supershell of hydrogen from supernova
explosions within the association.
Menkib illuminates and ionizes a portion
of this shell, creating a wonder resem-
bling the most populous U.S. state — the
California Nebula (NGC 1499).
Recently, astronomers have recognized
the California Nebula as a major molecu-
lar cloud complex unto itself.American astronomer Edward
Emerson Barnard discovered this swath
of emission nebulosity in 1884 while
using a 6-inch refractor to sweep for
comets north-northeast of Menkib.
Dark skies are required to see the ill-
defined glow, which appears as a 2.5°-
by-0.5° “wall” of celestial mist that more
than fills most low-power eyepieces.
Seeing it well requires low power, a wide
field, and careful sweeping techniques.
A Hydrogen-beta filter will enhance the
view dramatically, especially through
binoculars. Can you see it with your
unaided eyes with that filter?
A wide and uneven double star, 40
Persei (Struve 431), lies about 3¾°The California Nebula is a faint, large area of
star formation that is difficult to observe
visually but can be photographed routinely
under dark skies. JASON WARE