- Chris Baker
Object of the Month: The Witch's Broom Nebula
Each month I highlight one of my images - giving more background to what you are looking at and how I photographed it. September 2022 I have chosen The Witch's Broom Nebula
My Image of the beautiful the Witch's Broom
About The Witch's Broom
A few thousand years BC a star more massive than our sun exploded violently, giving out enough light to have been visible for a few days from the Earth during daylight. This was a Super Nova explosion and ever since the remains have continued to travel at many thousands of miles per second across interstellar space. This is what is known as a Super Nova remnant. The colossal energy lights up its path as it collides with interstellar dust, creating a beautiful and stunning sight.
The Beauty of the nebulosity can be seen in these images
The Witch’s Broom is estimated to be 1,400 light years away so the light has taken that time to travel across our galaxy to my camera. To place the object, it is outside of our Solar System, i.e. beyond all the planets that orbit the Sun, but inside our Galaxy, which is known as The Milky Way.
The Witch’s Broom is just one section of a large Super Nova Remnant with the entire structure being known as ‘The Veil Nebula’. The Witch’s Broom is the western section and also has a less interesting catalogue number of NGC 6960. It was first identified in the late 18th century by a British astronomer William Herschel, working from Bristol.
Although this is the death of a star it is also the beginning of life as contained within Super Novae is what goes to form Stars, Planets, you and me.
Imaging The Witch's Broom
This object is extremely faint from Earth and not much light is reaching the telescope and camera. In addition it emits light at specific wavelengths associated with certain ionized states of gases.
I use specialist filters which capture certain emissions from these gases, in this case Hydrogen Alpha (Ha), Oxygen III (OIII) and Sulphur II (SII). Using my telescope and cameras I captured 10’s of hours of data through these three filters over many nights. Each exposure was 20 minutes and at the end of each night I discard the sub optimal images, such as when the seeing conditions were not perfect or a satellite crossed the field of view. Over time I build up the data for each filter and eventually have enough to start the long process of calibration and processing.
During this process I want to extract the beautiful detail that exists buried within the raw data and at the same time make it look stunning for the Galaxy on Glass range. I use a convention to assign the colours developed for the Hubble Space telescope. This means that I assign the SII to the red channel, Ha to the green and OIII to the blue channel. You will see in this picture that there is a lot of blue, meaning the object is emitting a lot of light associated with the Oxygen. Using this convention shows rich blues and golds and the wispy details of the nebulosity.
To see all options for The Witch's Broom click HERE
I hope you love this piece and have one on your wall! Chris Baker.