RCW 138 is an emission nebula (H II region) in Sagittarius
RCW 138 is an emission nebula (H II region) in the constellation Sagittarius . spans 8′. It is a telescope object, 6 inches or larger, and it is highest in the evening sky in August.
Nebula: a cloud of gas and dust. Emission nebulae glow on their own, lit by ultraviolet light from hot young stars; reflection nebulae shine by starlight scattered from dust; dark nebulae block the light behind them.
Finding RCW 138 from Alnasl
Alnasl
RCW 138
SAGITTARIUS
RCW 138 lies 4.8° west of Alnasl , the magnitude 3.0 star. Three fingers held at arm's length cover about 5°.
RCW 138 is highest in the evening in August
JAN
FEB
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APR
MAY
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JUL
AUG
SEP
OCT
NOV
DEC
60°N
JAN at 60°N: -57° high at 9 pm FEB at 60°N: -57° high at 9 pm MAR at 60°N: -48° high at 9 pm APR at 60°N: -34° high at 9 pm MAY at 60°N: -19° high at 9 pm JUN at 60°N: -7° high at 9 pm JUL at 60°N: -0° high at 9 pm AUG at 60°N: 1° high at 9 pm SEP at 60°N: -6° high at 9 pm OCT at 60°N: -17° high at 9 pm NOV at 60°N: -31° high at 9 pm DEC at 60°N: -46° high at 9 pm 50°N
JAN at 50°N: -65° high at 9 pm FEB at 50°N: -66° high at 9 pm MAR at 50°N: -52° high at 9 pm APR at 50°N: -33° high at 9 pm MAY at 50°N: -15° high at 9 pm JUN at 50°N: 0° high at 9 pm JUL at 50°N: 9° high at 9 pm AUG at 50°N: 10° high at 9 pm SEP at 50°N: 2° high at 9 pm OCT at 50°N: -12° high at 9 pm NOV at 50°N: -30° high at 9 pm DEC at 50°N: -49° high at 9 pm 40°N
JAN at 40°N: -72° high at 9 pm FEB at 40°N: -74° high at 9 pm MAR at 40°N: -54° high at 9 pm APR at 40°N: -31° high at 9 pm MAY at 40°N: -10° high at 9 pm JUN at 40°N: 8° high at 9 pm JUL at 40°N: 19° high at 9 pm AUG at 40°N: 20° high at 9 pm SEP at 40°N: 10° high at 9 pm OCT at 40°N: -6° high at 9 pm NOV at 40°N: -27° high at 9 pm DEC at 40°N: -50° high at 9 pm 30°N
JAN at 30°N: -75° high at 9 pm FEB at 30°N: -78° high at 9 pm MAR at 30°N: -54° high at 9 pm APR at 30°N: -28° high at 9 pm MAY at 30°N: -5° high at 9 pm JUN at 30°N: 16° high at 9 pm JUL at 30°N: 29° high at 9 pm AUG at 30°N: 30° high at 9 pm SEP at 30°N: 18° high at 9 pm OCT at 30°N: -1° high at 9 pm NOV at 30°N: -24° high at 9 pm DEC at 30°N: -49° high at 9 pm 20°N
JAN at 20°N: -72° high at 9 pm FEB at 20°N: -75° high at 9 pm MAR at 20°N: -51° high at 9 pm APR at 20°N: -25° high at 9 pm MAY at 20°N: 0° high at 9 pm JUN at 20°N: 23° high at 9 pm JUL at 20°N: 38° high at 9 pm AUG at 20°N: 40° high at 9 pm SEP at 20°N: 26° high at 9 pm OCT at 20°N: 5° high at 9 pm NOV at 20°N: -20° high at 9 pm DEC at 20°N: -46° high at 9 pm 10°N
JAN at 10°N: -66° high at 9 pm FEB at 10°N: -67° high at 9 pm MAR at 10°N: -47° high at 9 pm APR at 10°N: -20° high at 9 pm MAY at 10°N: 5° high at 9 pm JUN at 10°N: 30° high at 9 pm JUL at 10°N: 47° high at 9 pm AUG at 10°N: 49° high at 9 pm SEP at 10°N: 33° high at 9 pm OCT at 10°N: 10° high at 9 pm NOV at 10°N: -16° high at 9 pm DEC at 10°N: -42° high at 9 pm 0°
JAN at 0°: -57° high at 9 pm FEB at 0°: -58° high at 9 pm MAR at 0°: -41° high at 9 pm APR at 0°: -16° high at 9 pm MAY at 0°: 10° high at 9 pm JUN at 0°: 36° high at 9 pm JUL at 0°: 56° high at 9 pm AUG at 0°: 59° high at 9 pm SEP at 0°: 40° high at 9 pm OCT at 0°: 15° high at 9 pm NOV at 0°: -11° high at 9 pm DEC at 0°: -36° high at 9 pm 10°S
JAN at 10°S: -48° high at 9 pm FEB at 10°S: -49° high at 9 pm MAR at 10°S: -34° high at 9 pm APR at 10°S: -11° high at 9 pm MAY at 10°S: 15° high at 9 pm JUN at 10°S: 42° high at 9 pm JUL at 10°S: 65° high at 9 pm AUG at 10°S: 68° high at 9 pm SEP at 10°S: 46° high at 9 pm OCT at 10°S: 20° high at 9 pm NOV at 10°S: -6° high at 9 pm DEC at 10°S: -30° high at 9 pm 20°S
JAN at 20°S: -39° high at 9 pm FEB at 20°S: -39° high at 9 pm MAR at 20°S: -27° high at 9 pm APR at 20°S: -5° high at 9 pm MAY at 20°S: 19° high at 9 pm JUN at 20°S: 46° high at 9 pm JUL at 20°S: 71° high at 9 pm AUG at 20°S: 76° high at 9 pm SEP at 20°S: 50° high at 9 pm OCT at 20°S: 24° high at 9 pm NOV at 20°S: -1° high at 9 pm DEC at 20°S: -23° high at 9 pm 30°S
JAN at 30°S: -29° high at 9 pm FEB at 30°S: -30° high at 9 pm MAR at 30°S: -19° high at 9 pm APR at 30°S: 0° high at 9 pm MAY at 30°S: 23° high at 9 pm JUN at 30°S: 49° high at 9 pm JUL at 30°S: 74° high at 9 pm AUG at 30°S: 79° high at 9 pm SEP at 30°S: 53° high at 9 pm OCT at 30°S: 28° high at 9 pm NOV at 30°S: 4° high at 9 pm DEC at 30°S: -16° high at 9 pm 40°S
JAN at 40°S: -19° high at 9 pm FEB at 40°S: -20° high at 9 pm MAR at 40°S: -11° high at 9 pm APR at 40°S: 6° high at 9 pm MAY at 40°S: 26° high at 9 pm JUN at 40°S: 50° high at 9 pm JUL at 40°S: 71° high at 9 pm AUG at 40°S: 75° high at 9 pm SEP at 40°S: 53° high at 9 pm OCT at 40°S: 31° high at 9 pm NOV at 40°S: 9° high at 9 pm DEC at 40°S: -8° high at 9 pm
below horizon
low
20-40°
40-60°
overhead-ish
The chart gives its height above the horizon at 9 pm through the year, from 60°N to 40°S. It can be seen from the whole southern hemisphere and north to about 61°N, and never sets south of 61°S.
The distance to RCW 138 is not well measured
Objects within 6° of RCW 138
RCW 135, planetary nebula, 1.4° NGC 6451, open cluster, 1.8° RCW 134, emission nebula (H II region), 2.6° M6 Butterfly Cluster, open cluster, 3.5° RCW 143, emission nebula (H II region), 3.9° RCW 136, planetary nebula, 4.0° NGC 6520, open cluster, 4.2° NGC 6522, globular cluster, 4.2°
RCW 138 catalog data
Field Value
Type emission nebula (H II region) Constellation Sagittarius Right ascension (J2000) 17h 45.0m Declination (J2000) -28° 51′ Apparent size 8′ Best month August Best with Telescope RCW number RCW 138
