Lagoon Nebula: Definition, Distance, Visibility, Formation
Lagoon Nebula is a star-forming region located 5,000 light-years away, one of two star nurseries visible without magnification. The active stellar nursery stretches across about 130 light-years and is visible in mid to late summer. The Lagoon Nebula is catalogued as Messier 8 and is located in the constellation Sagittarius. The nebula has an apparent magnitude of 6.
What is the Lagoon Nebula?
The Lagoon Nebula is a giant emission nebula which is catalogued as Messier 8 and NGC 6523. It is located in Sagittarius and is an interstellar gas cloud that is star-forming with an H II region. The Lagoon Nebula has an apparent magnitude of 6.
Messier 8, catalogued as M8 and commonly known as the Lagoon Nebula, is a giant emission nebula classified as a diffuse nebula and an H II region. Located 5,200 light-years from Earth in the constellation Sagittarius, it spans 33 light-years across and glows at visual magnitude 6.0, making it one of only two star-forming nebulae faintly visible to the naked eye from mid-northern latitudes. With binoculars or telescopes the nebula’s faint nebulosity appears grayish, while long-exposure photographs reveal pink and reddish hues.
The Lagoon Nebula is an active stellar nursery composed primarily of hydrogen, and massive stars embedded within it give off enormous amounts of ultraviolet radiation that ionize the gas and cause the nebula to shine. Among these hot stars, Herschel 36 provides the principal ionizing ultraviolet radiation. The nebula contains the embedded open star cluster NGC 6530, whose hot stars further power the nebular glow. It includes the Hourglass Nebula, a striking feature near its center. Extensive curling shadowy dust clouds almost divide the nebula in half, and numerous dark Bok Globules associated with M8 mark sites of future star birth. Discovered in 1654 by Giovanni Battista Hodierna and later catalogued by Charles Messier, the Lagoon Nebula remains a key deep-sky object for studying star formation.
Are the Lagoon Nebula and Trifid visible together?
Yes. The Lagoon Nebula and the Trifid Nebula appear in the same field of view because Trifid Nebula (M20) is 1.4° north-northwest of the Lagoon Nebula. Both lie within the constellation Sagittarius, so a binocular or small-telescope sweep across that area shows the Lagoon Nebula below Trifid Nebula in this image. Observers can frame the pair together, capturing dark dust lanes and the glowing gas that make these two emission nebulae a convenient dual sight in summer skies.
How far is the Lagoon Nebula?
The Lagoon Nebula lies about 5,000 light-years away.
How large is the Lagoon Nebula?
The Lagoon Nebula’s bright inner cloud measures roughly 55 × 110 light-years, a span that widens to about 115 light-years once the fainter outer envelope is included. The whole structure covers an area 130 light-years long. In Earth’s sky this emission nebula presents an oval 90′ × 40′ across, an apparent size roughly three times that of the full Moon.
How many stars are in the Lagoon Nebula?
The open star cluster NGC 6530, immersed in the Lagoon Nebula, contains 3,675 candidate members, of which 2,728 are judged to be likely members. In 1919 C. O. Lampland identified 18 irregularly variable stars scattered through the nebula beyond the cluster boundary.
Massive stars embedded within the nebula, among them Herschel 36 near the centre, give off ultraviolet radiation that powers the nebular glow and continues the region’s vigorous star-forming activity.
When is the Lagoon Nebula visible?
The Lagoon Nebula is best observed during the summer months of June through August, with July offering the finest views. From mid-northern latitudes it appears low in the south, never climbing more than about 6° above the horizon, so a site free of obstructions and light pollution is vital. Under such dark skies the nebula is faintly visible to the naked eye as a small, grey streak of light. An averted vision helps with visibility. Binoculars or any small telescope immediately reveal its glowing cloud and the dark dust lane that bisects it.
How did the Lagoon Nebula form?
Astronomers probing the Messier 8 cloud have found the first unambiguous proof that star formation by accretion of matter from the gas cloud is ongoing in this region. Optical, infrared and submillimetre-wave emission indicate ongoing star formation in several locations across the Lagoon. Bok globules are dark collapsing clouds of protostellar material embedded within the nebula and suggest ongoing processes of stellar birth and evolution. Modern infrared observations confirmed active star formation within these globules. Herbig-Haro objects provide direct evidence of accretion processes within the Hourglass structure where four such objects have been detected. Young stars still surrounded by an accretion disc shoot out long tendrils of matter from their poles and sculpt the nebula while ultraviolet radiation ionizes gas of the Lagoon Nebula. Massive stars form from the nebula and shape its dust clouds resulting in the dynamic structures observed today.
