Sunday, May 30, 2021

Exploring the Lagoon nebula

The Lagoon Nebula (also known as Messier 8, NGC 6523, Sharpless 25, RCW 146, and Gum 72) is an emission nebula and an HII region, located in the constellation of Sagittarius. Its distance estimates range between 4,000-6,000 light years.

This is a giant interstellar cloud with an elliptical morphology having a radius that varies from 20 to 55 light years. The Lagoon is a region of star formation and within it, numerous massive OB stars are present that are responsible for its illumination.

Since the improval of telescope and instrumentation technology, Bok globules and Herbig-Haro objects have been detected in the region, thus confirming active star formation. Additionally, phenomena due to the presence of massive stars in a cloud have been studied. Perhaps one of the most impressive is a tornado-like structure that is formed from the immense ultraviolet emission of an O type star. Its radiation pressure and stellar wind push the gas in its immediate environment, thus forming such structure.

Image 1: Composite image of the Lagoon Nebula taken with the 8-metre Gemini South Telescope in Chile. A region located in the southern Lagoon Nebula which is known as the "Southern Cliff", can be seen here. The image was created using narrow band filters that are focused on the emission of ionized hydrogen (Hα, red) and ionized sulfur ([S II], green), together with a broadband filter that is centred at around 800 nm (I-band, blue). Here we can see a spectacular mixture of gas and dust, where low and intermediate mass stars are formed. The majority of the newborn stars are embedded at the tips of the thick dusty clouds that appear here as bright-rimmed pillars. A dozen of Herbig-Haro objects have detected in this image with sizes that range from a few thousands astronomical units (one astronomical unit is the mean Earth-Sun distance) to 4.5 light years (this similar to the distance between the Sun and the closest star to our Solar system, Proxima Centauri). 

Image 2: Composite optical image of the Lagoon Nebula. The “Southern Cliff” is superimposed in this wide field of view image.

Image 1 Credit: Julia I. Arias and Rodolfo H. Barbá Departamento de Física, Universidad de La Serena (Chile), and ICATE-CONICET (Argentina).

Image 2 Credit: R. Barba, N. Morrell et al. (UNLP), CTIO, NOAO, NSF


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