Starwatch: Something shocking in the Lagoon

If we imagined the Lagoon Nebula to be a tranquil pool floating between the stars, this image from the Gemini South telescope in the Chilean Andes might come as a shock.

Indeed, the bright fringes evident around the nebula’s clouds of gas and dust are quite literally shock fronts formed when speeding jets of material from new-born stars crash into the surrounding material. Friction, and the ultraviolet radiation from the stars, causes the gas to glow. The shocks also stir up the gas, helping to create pockets of higher density which can collapse under gravity to make new stars and planets.

Obtained by the Argentinean astronomers Julia Arias and Rodolfo Barbá, the false-colour image shows only a portion of the nebula. It was obtained by combining separate images taken through filters sensitive to the light of hydrogen (the red component in the image), ionised sulphur (shown as green) and the far red radiation, beyond what the human eye can perceive, as blue. The research is investigating how the stars and the luminous patches their jets create, so-called Herbig-Haro objects, evolve over time.

It does seem, though, that each Herbig-Haro object lives for only a few thousand years. Since the Lagoon lies some 5,000 light years away, its fine structure appearance might look quite different if we could see it as it is now, rather than 5,000 years ago.

Considered one of the gems in the night sky, the Lagoon is one of only two star-forming regions visible to the naked eye from our northern latitudes, the other being the Orion Nebula. It is far from easy, though, appearing as a dim grey disc rather larger than the Moon but so far south that it never climbs higher than 14° in the S as seen from London. Telescopes show it spangled with a multitude of young stars and slashed by a dark lane of obscuring gas and dust.

It lies in Sagittarius, just above the spout of the Teapot, and stands only a degree or so to the right of the Moon (and is obliterated by the moonlight) on Thursday night. It is also well known as Messier 8, or M8, after its place in Charles Messier‘s list of fuzzy celestial objects which were not to be confused with the comets that were his particular passion. Ironically, Messier is now remembered more fondly for this list of “rejects” than for the 13 comets that bear his name.

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