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.