M8 (Lagoon nebula) and M20 (Trifid nebula) in Sagittarius

M20M8 copia

  • Telescope: Canon EF 135mm f/2L USM telephoto lens (f/2.8 stopped)
  • Camera: Baader modified Canon 400D, 800 iso, RAW mode
  • Mount: Astrotrac with polar scope
  • Integration: 35 x 120 sec, (25 bias, 25 dark, 25 flat)
  • Date, Location, Temp/Software: August 2019, Livorno (Italy), 25°C/MaxIm-DL, PixInsight, PhotoShop
  • Click the image for 1920×1080 resolution

M8 and M20 nebulae. M8, the Lagoon nebula, is a giant interstellar cloud in the constellation Sagittarius. It is classified as an emission nebula and as an H II region. The Lagoon Nebula is estimated to be between 4,000-6,000 light-years from the Earth. In the sky of Earth, it spans 90′ by 40′, which translates to an actual dimension of 110 by 50 light years. Like many nebulas, it appears pink in time-exposure color photos but is gray to the eye peering through binoculars or a telescope, human vision having poor color sensitivity at low light levels. The nebula contains a number of Bok globules (dark, collapsing clouds of protostellar material), the most prominent of which have been catalogued by E. E. Barnard as B88, B89 and B296. It also includes a funnel-like or tornado-like structure caused by a hot O-type star that emanates ultraviolet light, heating and ionizing gases on the surface of the nebula. The Lagoon Nebula also contains at its centre a structure known as the Hourglass Nebula (so named by John Herschel), which should not be confused with the better known Engraved Hourglass Nebula in the constellation of Musca. In 2006 the first four Herbig–Haro objects were detected within the Hourglass, also including HH 870. This provides the first direct evidence of active star formation by accretion within it. M20, the Trifid nebula is an H II region located in Sagittarius. Its name means ‘divided into three lobes’. The object is an unusual combination of an open cluster of stars; an emission nebula (the lower, red portion), a reflection nebula (the upper, blue portion) and a dark nebula (the apparent ‘gaps’ within the emission nebula that cause the trifurcated appearance. The close-up images show a dense cloud of dust and gas, which is a stellar nursery full of embryonic stars. This cloud is about 8 ly away from the nebula’s central star. A stellar jet protrudes from the head of the cloud and is about 0.75 ly long. The jet’s source is a young stellar object deep within the cloud. Jets are the exhaust gasses of star formation and radiation from the nebula’s central star makes the jet glow.

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