NGC 604
A supergiant H II region in the Triangulum Galaxy.
NGC 604, a supergiant H II region in the Triangulum Galaxy, was first observed by William Herschel on September 11, 1784. It ranks among the largest such regions in the Local Group. At the galaxy’s estimated distance of 2.7 million light-years, its longest diameter spans roughly 1,520 light-years (about 460 parsecs)—over 40 times the visible extent of the Orion Nebula. Its luminosity exceeds that of the Orion Nebula by more than 6,300 times; placed at the same distance, it would outshine Venus. The gas within NGC 604 is ionized by a central cluster of massive stars, containing 200 stars of spectral types O and WR, with a total mass of 105 solar masses and an age of 3.5 million years. Unlike the Tarantula Nebula’s central cluster (R136) in the Large Magellanic Cloud, this cluster is far less compact and more closely resembles a large stellar association.
Quick Facts
- Epoch
- J2000
- Ra
- 01 · 34 · 33.2
- Dec
- +30 · 47 · 06
- Dist Ly
- 2,700,000
- Dist Pc
- 840,000
- Appmag V
- +14.0
- Constellation
- Triangulum
- Radius Ly
- 760
- Absmag V
- -13.8
- Notes
- massive supergiant H II region / 3.5 million years old
Facts from the source article.
Lore & Background
NGC 604 was discovered by William Herschel on September 11, 1784. At the galaxy's estimated distance of 2.7 million light-years, its longest diameter is roughly 1,520 light-years (about 460 parsecs), making it over 40 times the size of the visible portion of the Orion Nebula. It is over 6,300 times more luminous than the Orion Nebula; if it were at the same distance, it would outshine Venus. The gas in NGC 604 is ionized by a central cluster of massive stars containing 200 stars of spectral type O and Wolf–Rayet, with a total mass of 105 solar masses and an age of 3.5 million years. Unlike the Tarantula Nebula's central cluster (R136) in the Large Magellanic Cloud, NGC 604's cluster is much less compact and more similar to a large stellar association.
Reader's Guide
NGC 604 stands as one of the most prominent H II regions in the Local Group, offering a nearby laboratory for studying massive star formation and the interaction of hot, young stars with their surrounding gas. Its enormous size—over 40 times the visible portion of the Orion Nebula—and extreme luminosity highlight the scale of star-forming regions in spiral galaxies beyond the Milky Way. The central cluster of 200 O-type and Wolf–Rayet stars, with a combined mass of 105 solar masses and an age of 3.5 million years, provides insight into the evolution of massive stellar associations. The region's less compact structure compared to the Tarantula Nebula's core suggests a different mode of star cluster formation. Observations combining visible light from the Hubble Space Telescope and X-rays from Chandra have revealed the nebula's intricate structure and the energetic processes at work. NGC 604 remains a key object for understanding the lifecycle of giant molecular clouds and the feedback from young, massive stars on galactic scales.
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