The Trifed Nebula, or M20, is a nebula located 9,000 light-years away from Earth in the constellation Sagittarius. It can be
spotted with a small telescope and is best observed during August. It is 2,000 to
9,000 light years away. Its diameter is 50 light years.
Sagittarius is one of the prominent features of the summer skies in the
northern hemisphere. In Europe north of the Pyrenees it drags very low along the
horizon and can be difficult to see clearly. In Scotland and Scandinavia it cannot be
seen at all. In southern Brazil, South Africa, and central Australia, Sagittarius
passes directly overhead.
The Milky Way is at its densest near Sagittarius, as this is where the galactic
center lies. As a result, Sagittarius contains many star clusters and nebulae.
The nebulae, include the Lagoon Nebula, the Omega Nebula, and the Trifid Nebula, a
large nebula containing some very young, hot stars.
The Lagoon Nebula is an emission nebula that is located 5,000 light-years from Earth and measures 140 light-years by 60 light-years. Though it appears grey in telescopes to
the unaided eye, long-exposure photographs reveal its pink hue, common to emission nebulae. It is fairly bright, with an
integrated magnitude of 3.0. The The central area of the Lagoon Nebula is also known as the Hourglass Nebula, so named for its distinctive shape. The Lagoon Nebula was
instrumental in the discovery of Bok globules, as Bart Bok studied prints of the nebula intensively in 1947.
Approximately 17,000 Bok globules were discovered in the nebula nine years later as a part of the Palomar Sky Survey; studies later showed that Bok's hypothesis that the globules
held protostars was correct.
To celebrate its 28th anniversary in space the NASA/ESA Hubble Space Telescope took this amazing and
colourful image of the Lagoon Nebula. The whole nebula, about 4000 light-years away, is an incredible
55 light-years wide and 20 light-years tall.
The region is filled with intense winds from hot stars, churning funnels of gas, and energetic star formation,
all embedded within an intricate haze of gas and pitch-dark dust.
The Omega Nebula is a fairly bright nebula, sometimes called the
Horseshoe Nebula or Swan Nebula. It has an integrated magnitude of 6.0 and
is 4890 light-years from Earth.
The Trifid Nebula is an emission nebula in Sagittarius. It is located between 2,000 and 9,000
light-years from Earth and has a diameter of approximately 50 light-years. The outside of the
Trifid Nebula is a bluish reflection nebula; the interior is pink with two dark bands that divide it
into three areas, sometimes called lobes. Hydrogen in the nebula is ionized, creating its characteristic color, by a central triple star, which formed in the intersection of the two dark bands. It is part of a
cluster that has a magnitude of 6.3.
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.
• This Hubble image reveals a cloud of gas and dust in the Trifed nebula being torn apart by radiation from a massive nearby star, just beyond the top of the frame. Two thin, finger-like jets protrude from the head of a dense cloud in the upper left of the image. The jets, each roughly three-quarters of a light-year long, are being eroded by the radiation from the massive star. The red in this image represents hydrogen and sulfur, while green represents oxygen.
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