ESO has released one of the largest astronomical images created thanks to the VST (Very Large Telescope Survey Telescope) which includes two cosmic clouds of gas and dust, NGC 6334 and NGC 6357. Because of their shapes, they’re also known respectively with their popular names as the “Cat’s Paw Nebula” and the “Lobster Nebula”.
The NGC 6334 and NGC 6357 nebulae were discovered by British scientist John Herschel in 1837 but the instruments he had available at the time were too limited to see them completely. Only decades later it was possible to see the true form of these two nebulae and give them popular names. Today we know that NGC 6334 is about 5,500 light years away from Earth while NGC 6357 is about 8,000 light years away from Earth.
The OmegaCAM camera installed on VST is used to conduct wide surveys at visible light taking photos of large areas of the sky. The image of the nebulae NGC 6334 and NGC 6357 in its original size has a 49,511 x 39,136 pixel resolution for a total of nearly 2 billion pixels and on ESO’s website there are versions available in various formats with sizes far larger than a GByte.
The NGC 6334 Cat’s Paw Nebula is one of the most active stellar incubators containing thousands of stars often massive, with masses that can be up to ten times the Sun’s. However, their light at visible frequencies is often hidden by the dust and gas surrounding them while for example another ESO’s telescope, VISTA, can detect their infrared emissions.
The NGC 6357 Lobster Nebula is also a stellar incubator and in fact is a sort of cluster of clusters as it contains at least three star clusters containing massive young stars. At certain infrared frequencies part of NGC 6357 looks more like a skull and another one looks like a dove so someone nicknamed it “War and Peace Nebula”.
The ultraviolet light emitted by the massive stars in the NGC 6334 and NGC 6357 nebulae affects the hydrogen atoms present in them ionizing them. There are large objects which shine due to the light produced by the ionization and are called emission nebulae. The various sources of light give the two nebulae their appearance all the more spectacular because there appear close to each other.
Despite the observations made with instruments that can detect infrared emissions, the mapping of the NGC 6334 and NGC 6357 nebulae is still far from complete because part of their content remains hidden. For this reason, their studies will continue, also with the instruments that will become operational in the future.