The Great Nebula in Orion is a vast cloud of gas and dust in
which new stars are being born. Located at the middle of
Orion’s Sword—a line of stars “hanging” beneath Orion’s
Belt--this stellar nursery lies about 1270 light years away,
and is about 30 light years across. From Earth, the nebula
covers an area of the sky four times greater than the Full
Moon. The visible part of the nebula, however, is actually
a small part of a much larger cloud, which spans more than
10 degrees of the sky, covering half of the constellation of
Orion.
Observational History of M-42
The center “star” in the “sword” of
the constellation Orion appears fuzzy to the human eye. In
1610, Nicholas-Claude Fabri de Peiresc discovered, through
his small telescope, that this star appeared to be made of
two stars and a wispy nebula.
 The first known drawing of
this object (right) was made sometime before 1654, by Giovanni
Batista Hodierna, who spotted a third star in the group.
This object would later be named the Great Nebula in
Orion—one of the first nebulae discovered, drawn, and
photographed, at different times in the past 400 years.
 In
1777, Charles Messier made a highly detailed drawing of the
Great Nebula in Orion and the stars it contained. He wanted
to determine if, over time, the shape of the nebula changed.
Left: 1777 drawing
of M-42 by Charles Messier.
In 1789, Sir William Herschel, from
observations through his large, self-made telescope, made an
almost prophetic description of the nebula as “an unformed
fiery mist, the chaotic material of future suns.”
The gaseous nature of the Orion
Nebula was revealed in 1865 with the help of spectroscopy by
William Huggins, and in 1880 it became the first nebula to
be successfully photographed, by Henry Draper.
Today, we understand the Great
Nebula in Orion as a stellar “nursery:” a vast cloud of gas
and dust containing some of the youngest stars ever
observed. These young stars energetically blow gas into
space, which encounter the surrounding gases of the nebula
to form an s-shaped boundary, called a “bow shock.”
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