The gas in NGC 604, which is about nine-tenths hydrogen, gradually collapses under gravity, giving rise to new stars. It follows that none or very few of the massive stars in this region of NGC 604 must have exploded as supernovae. The nebula also provides clues to its star formation history and will improve understanding of the starburst process, when a galaxy experiences a “firestorm” of star formation. This is a Hubble Space Telescope image (right) of a giant nebula called NGC 604, located in the neighbouring spiral galaxy Messier 33, 2.7 million light years away in the constellation Triangulum.
A new study reveals NGC 604, the largest region of star formation in the nearby galaxy M33, in its first deep, high-resolution view in X-rays.
What is NGC 604 in the galaxy?
Although such nebulae are common in galaxies, this one is particularly large, at nearly 1,500 light-years across.
How was NGC 604 discovered?
The spectra within the H ii region of NGC 604, delineated by the blue ellipse in Figure 6, show a relatively large velocity dispersion, with the double-peaked profiles clearly visible outside the ellipse, implying that the complex velocity structure is due not only to the feedback effect of the central cluster, but also to the large-scale gas merging of the two velocity components. The velocity separation between the two components is ∼50 km s-1 for R 136, which is about a factor of 2-3 larger than in the present case of NGC 604.The spectra within the H ii region of NGC 604, delineated by the blue ellipse in Figure 6, show a relatively large velocity dispersion, with the double-peaked profiles clearly visible outside the ellipse, implying that the complex velocity structure is not only due to the feedback effect of the central cluster, but also to the large-scale gas merger of the two velocity components. The velocity separation between the two components is ∼50 km s-1 for R 136, which is about a factor of 2-3 larger than in the present case of NGC 604.Position-velocity diagram in the direction of the region that includes the H i cavity around NGC 604 and the expansion cloud. As the mass accretion continued, the collisions of the H i clouds triggered the formation of the supermassive star cluster of NGC 604 a few Myr ago.
What is at the centre of NGC 2392?
The term is simply a historical relic, as these objects looked like planetary disks to astronomers looking through small optical telescopes in the past. Using data from the Chandra X-ray Observatory and NASA’s Hubble Telescope, astronomers studied NGC 2392 and two other planetary nebulae with hot gas at their centres and found that NGC 2392 emits an unusual amount of X-rays compared to the other two. The Eskimo Nebula (NGC 239 , also known as the Clown Nebula, Lion Nebula or Caldwell 39) is a bipolar double-shell planetary nebula (PN). Today, astronomers with space-based telescopes are able to observe planetary nebulae such as NGC 2392 in ways that their scientific ancestors probably could not have imagined.
