RCW 21 is a planetary nebula in Vela, 7,180 light-years away
RCW 21 (PN G257.5+00.6) is a planetary nebula in the constellation Vela , 7,180 light-years away. spans 1′ of sky, about 2.1 light-years across. It is a telescope object, 6 inches or larger, and it is highest in the evening sky in March.
Planetary nebula: a shell of gas thrown off by a dying Sun-like star and lit by the hot core left behind, which becomes a white dwarf. The name comes from their small, round, planet-like look in early telescopes.
Finding RCW 21 from Naos
Naos
RCW 21
VELA
RCW 21 lies 5.6° east of Naos , the magnitude 2.2 star. Three fingers held at arm's length cover about 5°.
RCW 21 is highest in the evening in March
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60°N
JAN at 60°N: -19° high at 9 pm FEB at 60°N: -11° high at 9 pm MAR at 60°N: -8° high at 9 pm APR at 60°N: -11° high at 9 pm MAY at 60°N: -20° high at 9 pm JUN at 60°N: -33° high at 9 pm JUL at 60°N: -47° high at 9 pm AUG at 60°N: -62° high at 9 pm SEP at 60°N: -68° high at 9 pm OCT at 60°N: -61° high at 9 pm NOV at 60°N: -46° high at 9 pm DEC at 60°N: -32° high at 9 pm 50°N
JAN at 50°N: -12° high at 9 pm FEB at 50°N: -2° high at 9 pm MAR at 50°N: 2° high at 9 pm APR at 50°N: -2° high at 9 pm MAY at 50°N: -13° high at 9 pm JUN at 50°N: -29° high at 9 pm JUL at 50°N: -47° high at 9 pm AUG at 50°N: -66° high at 9 pm SEP at 50°N: -78° high at 9 pm OCT at 50°N: -65° high at 9 pm NOV at 50°N: -46° high at 9 pm DEC at 50°N: -28° high at 9 pm 40°N
JAN at 40°N: -5° high at 9 pm FEB at 40°N: 8° high at 9 pm MAR at 40°N: 12° high at 9 pm APR at 40°N: 7° high at 9 pm MAY at 40°N: -6° high at 9 pm JUN at 40°N: -24° high at 9 pm JUL at 40°N: -45° high at 9 pm AUG at 40°N: -67° high at 9 pm SEP at 40°N: -88° high at 9 pm OCT at 40°N: -66° high at 9 pm NOV at 40°N: -43° high at 9 pm DEC at 40°N: -23° high at 9 pm 30°N
JAN at 30°N: 3° high at 9 pm FEB at 30°N: 17° high at 9 pm MAR at 30°N: 22° high at 9 pm APR at 30°N: 16° high at 9 pm MAY at 30°N: 2° high at 9 pm JUN at 30°N: -19° high at 9 pm JUL at 30°N: -41° high at 9 pm AUG at 30°N: -65° high at 9 pm SEP at 30°N: -82° high at 9 pm OCT at 30°N: -63° high at 9 pm NOV at 30°N: -39° high at 9 pm DEC at 30°N: -17° high at 9 pm 20°N
JAN at 20°N: 10° high at 9 pm FEB at 20°N: 26° high at 9 pm MAR at 20°N: 32° high at 9 pm APR at 20°N: 25° high at 9 pm MAY at 20°N: 9° high at 9 pm JUN at 20°N: -13° high at 9 pm JUL at 20°N: -36° high at 9 pm AUG at 20°N: -59° high at 9 pm SEP at 20°N: -72° high at 9 pm OCT at 20°N: -58° high at 9 pm NOV at 20°N: -34° high at 9 pm DEC at 20°N: -11° high at 9 pm 10°N
JAN at 10°N: 17° high at 9 pm FEB at 10°N: 35° high at 9 pm MAR at 10°N: 42° high at 9 pm APR at 10°N: 34° high at 9 pm MAY at 10°N: 16° high at 9 pm JUN at 10°N: -7° high at 9 pm JUL at 10°N: -30° high at 9 pm AUG at 10°N: -51° high at 9 pm SEP at 10°N: -62° high at 9 pm OCT at 10°N: -50° high at 9 pm NOV at 10°N: -28° high at 9 pm DEC at 10°N: -5° high at 9 pm 0°
JAN at 0°: 24° high at 9 pm FEB at 0°: 44° high at 9 pm MAR at 0°: 52° high at 9 pm APR at 0°: 43° high at 9 pm MAY at 0°: 23° high at 9 pm JUN at 0°: -1° high at 9 pm JUL at 0°: -23° high at 9 pm AUG at 0°: -43° high at 9 pm SEP at 0°: -52° high at 9 pm OCT at 0°: -42° high at 9 pm NOV at 0°: -22° high at 9 pm DEC at 0°: 1° high at 9 pm 10°S
JAN at 10°S: 31° high at 9 pm FEB at 10°S: 52° high at 9 pm MAR at 10°S: 62° high at 9 pm APR at 10°S: 51° high at 9 pm MAY at 10°S: 30° high at 9 pm JUN at 10°S: 6° high at 9 pm JUL at 10°S: -16° high at 9 pm AUG at 10°S: -35° high at 9 pm SEP at 10°S: -42° high at 9 pm OCT at 10°S: -34° high at 9 pm NOV at 10°S: -15° high at 9 pm DEC at 10°S: 7° high at 9 pm 20°S
JAN at 20°S: 37° high at 9 pm FEB at 20°S: 60° high at 9 pm MAR at 20°S: 72° high at 9 pm APR at 20°S: 58° high at 9 pm MAY at 20°S: 35° high at 9 pm JUN at 20°S: 12° high at 9 pm JUL at 20°S: -9° high at 9 pm AUG at 20°S: -26° high at 9 pm SEP at 20°S: -32° high at 9 pm OCT at 20°S: -25° high at 9 pm NOV at 20°S: -8° high at 9 pm DEC at 20°S: 13° high at 9 pm 30°S
JAN at 30°S: 42° high at 9 pm FEB at 30°S: 66° high at 9 pm MAR at 30°S: 82° high at 9 pm APR at 30°S: 64° high at 9 pm MAY at 30°S: 40° high at 9 pm JUN at 30°S: 18° high at 9 pm JUL at 30°S: -2° high at 9 pm AUG at 30°S: -16° high at 9 pm SEP at 30°S: -22° high at 9 pm OCT at 30°S: -16° high at 9 pm NOV at 30°S: -1° high at 9 pm DEC at 30°S: 19° high at 9 pm 40°S
JAN at 40°S: 46° high at 9 pm FEB at 40°S: 69° high at 9 pm MAR at 40°S: 88° high at 9 pm APR at 40°S: 66° high at 9 pm MAY at 40°S: 44° high at 9 pm JUN at 40°S: 23° high at 9 pm JUL at 40°S: 5° high at 9 pm AUG at 40°S: -7° high at 9 pm SEP at 40°S: -12° high at 9 pm OCT at 40°S: -7° high at 9 pm NOV at 40°S: 6° high at 9 pm DEC at 40°S: 24° 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 52°N, and never sets south of 52°S.
RCW 21 is 7,180 light-years away
The light seen from RCW 21 tonight left it about 7,180 years ago. It ranks 29 of 47 by distance among the RCW nebulae with a measured distance. Distance source: Gaia extinction distance, Deng et al. 2025 (2200 pc).
Objects within 6° of RCW 21
RCW 23, emission nebula (H II region), 1.2° RCW 25, emission nebula (H II region), 1.8° RCW 24, planetary nebula, 2.2° RCW 27, emission nebula (H II region), 2.4° RCW 20, emission nebula (H II region), 2.9° RCW 26, emission nebula (H II region), 3.1° RCW 32, emission nebula (H II region), 3.9° RCW 19, emission nebula (H II region), 4.0°
RCW 21 catalog data
Field Value
Designations PN G257.5+00.6 Type planetary nebula Constellation Vela Right ascension (J2000) 08h 30.9m Declination (J2000) -38° 18′ Apparent size 1′ True size 2.1 light-years Distance 7,180 light-years (Gaia extinction distance, Deng et al. 2025 (2200 pc)) Best month March Best with Telescope RCW number RCW 21
