Physics Photo of the Week
Horsehead Nebula - Processing and Discussion by Gina Warren
First recorded in 1888 at Harvard College Observatory, the
Horsehead Nebula is made of dust and non-luminous gas. It stands out as
a dark, swirling cloud in the sky, and was given it’s name because of
the obvious shape of a horse’s head and neck that it forms.
Also known as Barnard 33, the Horsehead Nebula is about 1600 light
years away, located in the constellation of Orion, just below Alnitak,
the left most star in Orion’s Belt. The Horsehead Nebula spans a
distance of approximately 2.7 by 1.8 light years and is part of the
optical nebula IC434. It is most visible in January.
To create this image of the Horsehead nebula, during one observation
session it was photographed with green, blue, and red filters (Gina
Warren, Emma Falcon, and Kendra Cole) on February 16, 2009.
Twenty-three pictures were taken for each color filter. The
multiple images for each color were superimposed on top of one another,
combining ("stacking") to make an image that accounted for the sum of
each color: blue, red, and green. By combining the pictures that we
took, the computer was able to remove cosmic rays and other forms of
Next these images were combined with a photograph of the Horsehead
Nebula’s luminosity which was taken and processed in December of 2008
(Brent Figlestahler, Melissa Hahn, Philip Hamilton, Jillian Levy,
and Rebecca Moss). The resulting image shows aspects of color and
luminosity. The red glow is due to hydrogen gas located behind the
nebula that’s being ionized by stars. The glow is the result of a
discreet emission spectrum in which electrons are emitting light as
they fall from high to low levels.
The February color observation was performed by students enrolled
in Earth, Light, and Sky class. The December observation was
performed by students enrolled in Contemporary Astronomy. Gina
Warren is a student enrolled in Earth, Light, and Sky.
Photo of the
published weekly during the academic year on Fridays by the Warren
Wilson College Physics
Department. These photos feature interesting phenomena in
the world around us. Students, faculty, and others are invited to
submit digital (or film) photographs for publication and
explanation. Atmospheric phenomena are especially welcome.
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