32 AUGUST 2019 • SKY & TELESCOPE
Wind-Blown Bubbles
Object WR No. HD Spectral Type Mag(v) Size RA Dec.
NGC 6888 136 192163 WN6 7.5 17 ′ 20 h 12.1m +38° 21′
W R 134 Nebula 134 191765 W N6 8.1 20 ′ 20 h 10.2m +36° 11′
Sh 2-308 6 50896 WN4 6.7–6.9 40 ′ 06 h 54.2m –23° 56′
NGC 2359 7 56925 WN4 11.6 27 ′ 07 h 18.5m –13° 13′
NGC 3199 18 89358 WN4 10.8 22 ′ 10 h 17.0m –57° 55′
WR 23 Nebula 23 92809 WC6 9.0 30 ′ 10 h 41.6m –58° 46′
NGC 2020 — 269748 WN4 13.2 3 ′ 05 h 33.2m –67° 43′
Angular sizes are from recent catalogs. Visually, an object’s size is often smaller than the cataloged value and varies according to the aperture and magnifi cation of the
viewing instrument. Right ascension and declination are for equinox 2000.0.Wolf-Rayet Nebulae
My 80-mm fi nder shows a 5′ roundish glow at 13×, and
higher power adds a portion of the wings. Through my
18-inch at 108×, the wispy central bubble has a brighter rim
along the west side, forming a thick semicircular C. Near the
north edge, three 12th-magnitude stars are aligned, and an
11th-magnitude star is attached at the south end. WR 7 is
offset northwest of center, near the bubble’s inner edge.
The helmet’s southern wing angles west-southwest as a
bright 4′ bar, then narrows and stretches west an additional
5 ′. The northern wing sprouts to the northwest and is slightly
broader and more uniform in surface brightness. A third,
dimmer fi lament shoots 10′ east from the north side of the
bubble. My 24-inch f/3.7 refl ector reveals a fi lamentary, mul-
tishell structure with knots and lacy arcs of nebulosity.
NGC 3199, dubbed the Southern Crescent, is one of
several showpieces in the constellation Carina. This nebula
lies too far south for most U.S. observers, but place it on your
bucket list for a trip near or south of the equator. From the
Cape of Good Hope, John Herschel described it as,the great falcated [sic k le -sh ap e d] nebula,
and remarked it wasbrighter to the south following [ea s t] part, and dies off to the
north preceding [west], having a curved form and forked tail.In deep optical images, NGC 3199 is the brightest part of
a complete wreath spanning 22′ in diameter. As we’ve seen
with other nebulae, the 11th-magnitude WR star HD 89358
is displaced 4.5′ west of the geometric center, and it’s nestled
within a small triangle of fainter stars. Distance estimates
range from 7,500 to 12,000 light-years, implying a physical
diameter of at least 50 light-years.
At a Costa Rica star party (latitude 10° north), NGC 3199
was faintly visible in my 9×50 fi nder as a nebulous bar. In a
13.1-inch refl ector, I saw an impressive kidney-shaped nebula,
extending 12′× 7 ′ north to south and opening to the east. The
southern half was brighter than the northern, and the inner
(eastern) edge was more sharply defi ned. Several 11th- and
12th-magnitude stars glittered on the southeast end. Despite
a careful look, I found no sign of the bubble’s eastern half.SOUTHERN CRESCENTIf you’re
a Northern Hemisphere observer,
you’ll have to travel south to see
NGC 3199, which lies in Carina.
This object has been much ob-
served, including by the European
Southern Observatory’s 2.6-meter
Very Large Survey Telescope,
which captured this image.ESO