skyandtelescope.com • NOVEMBER 2019 5932-inch refl ector. Using the usual for-
mula that correlates magnitude and dis-
tance, a very conservative absolute mag-
nitude of –6 places potential WR target
stars at a distance of 5.2 million light-
years, or just outside the Local Group
(with the Milky Way at the center) and
signifi cantly more distant than the WR
stars in NGC 2359 and NGC 6888. If I
were to fi nd a WR star with the absolute
magnitude of RW Cephei (–9.4), I could
be looking at an object potentially 25
million light-years away, similar to that
of M51 (the Whirlpool Galaxy). I stud-
ied papers on M51’s individual stars and
concluded that none are presently visible
with my equipment. Face-on spirals
away from the plane of our galaxy seem
best suited for the search, thus minimiz-
ing intragalactic extinction. And that
brought me to NGC 300.
Digging Deep in NGC 300
NGC 300 is a face-on Sc-type spiral gal-
axy in Sculptor with many star-forming
regions. Previously considered to be a
member of the Sculptor Group, it’s now
thought to be closer than that grouping
of galaxies. At a distance of 6.3 million
light-years or so, NGC 300 is gravita-
tionally paired with nearby NGC 55 and
is often likened to another late-type
spiral, M33 (the Triangulum Galaxy),
which is known to have an abundance
of WR stars. A 2003 paper published
by Hans Schild (ETH-Zentrum, Swit-
zerland) and coauthors dealt with 58
stars in NGC 300, of which 22 were
confi rmed WR stars and the rest were
newly identifi ed in their study. The
European Southern Observatory Very
Large Telescope’s 8.2-meter mirrors
and associated instruments allowed
the team to obtain deeper imaging and
spectroscopic data of the targets.
At the 2016 Okie-Tex Star Party,
I used my 32-inch f/4 refl ector on
the night of September 26th to view
NGC 300 and its WR stars. With a
9-mm Type 6 Nagler eyepiece yield-
ing 361× and a 14′ fi eld of view, I spent
40–50 minutes scanning the south-
ern half of the galaxy for these stellar
beacons from beyond the Local Group
and was able to make out four. I use
the same numbers as in the Schild
paper. The brightest of the new WR
candidates, #20, appeared as a stellar
dot 50′′ south-southwest of the galaxy’s
nucleus. The second brightest candidate
was #56, located 3.7′ east of the nucleus
at a position angle of 97°. It was the
most northerly of three objects forming
a right triangle and moderately easy at
magnitude 17.7.
The two confi rmed WR stars I
observed were #4 and #38. The former is
readily seen in a little clump 45′′ east of
a 9.6-magnitude star that is 2.6′ south-
west of the nucleus. This area also forms
a small right triangle of objects, with #4
sitting in the northwest corner. WR star
#38 is the faintest of the four on Schild’s
list, with a magnitude of 19.5. There is
a 13.8-magnitude star 3.2′ southeast
of the galaxy’s nucleus, and it forms a
triangle with two slightly fainter objects,
each 30′′ to the west-northwest and
southwest. The southwesternmost of
these three objects appears slightly nebu-lous, and the WR position correlates
with a faint stellaring (dense, starlike
knot) a few arcseconds northeast of the
main object. In the eyepiece the fea-
ture containing the WR star did appear
elongated, if not separated, from the rest
of the area. Twenty-inch instruments
should snag the candidates of magni-
tude 17–18, while refl ectors in the 25- to
30-inch range may be needed for #38.
Among the targets I didn’t attempt
this time was #41, a 22.4-magnitude
WR star near #56. The 26-solar-mass
WR star is most likely in a binary
pair with a 20-solar-mass black hole.
NGC 300 X-1, as it’s known, is only the
second such extragalactic pair identifi ed,
after IC 10 X-1. Can you make it out?
Most observing projects have a
specifi c, static object in mind, one that
can be pursued for as long as needed.
We know where it is and how to fi nd it,
with only circumstance needed for bet-
ter insight into its nature. But this one
is different. It’s an idea dependent on
dynamic factors, and fi nding new stellar
candidates for a distance record has been
an enriching process. Take a moment to
appreciate the present universe where a
mere star can be seen so far away.¢DAVE TOSTESON likes to expand the
visual limits of the observable universe.FURTHER READING: To learn more
about the observing procedures and
results on the WR stars in NGC 300, see
the paper by Hans Schild and colleagues
published in Astronomy & Astrophysics in
2003 at https://is.gd/NGC300_WR.#4#38#56