Myriad stars, bright and dark nebulae, and clusters lie
peppered throughout the bright winter constellation Perseus.
BY STEPHEN JAMES O’MEARA
Inside the PERSEUS MOL
This month, we’ll be pointing our
telescopes toward the Perseus spiral arm
of our galaxy near the galactic anticenter.
Specifically, we’ll stay within the 12°-by-
12° boundary of the Perseus Molecular
Cloud — the most active region of star
formation within 1,000 light-years of the
Sun. It’s not only a challenging proving
grounds for the visual observer, but also
a wonderland of celestial dreamscapes
for the astrophotographer.
The cloud contains the 6-million-
year-old Perseus OB2 Association,
a loosely organized moving group of
young, hot stars that includes a naked-
eye triangle of stars — 4th-magnitude
Menkib (Xi [ξ] Persei), 3rd-magnitude
Zeta (ζ) Persei, and 4th-magnitude Atik(Omicron [ο] Persei) — as well as 5th-
magnitude 40 Persei. So, the naked eye
alone can already spot the second-closest
OB association to the Sun, the first being
the Scorpius-Centaurus Association.
We’ll begin with one of those naked-eye
stars, Zeta Persei, which is a stunning, if
not baff ling, telescopic object.
Zeta Persei, the prime luminary of
the Per OB2 Association, often lends its
name to the association. This blue-white
supergiant, some 100,000 times more
luminous than our Sun, is also the mul-
tiple star system catalogued as Struve- But how many stars in this intrigu-
ing field are part of the system? Some
sources list two, while others list five.
This frustrating situation may cause
some to shy away from the field, but I
encourage you to simply enjoy the view
because it’s grand.
When I first looked at Zeta Persei
through my 8-inch ref lector at 45x, I
immediately saw two companions — a
pair of roughly 9.5-magnitude stars some
2' to its south. But greater magnification
revealed what is arguably Zeta’s only true
companion: a 9th-magnitude f leck of
ashen light 13.4" to the south-southwest
(at position angle 210°).
The great difference in magnitudes
will make this partner a challenge to see
through smaller telescopes, and experi-
ence has shown that poor seeing will
thwart chances in larger ones. So cool
Much of central Perseus glitters with bright blue
and white stars belonging to the Perseus OB2
Association. The bright stars near the center of
this image are members of this physical group.
The California Nebula lies near the bottom, the
Pleiades Cluster (in Taurus) below it, and the
Double Cluster near the top. TONY HALLAS