Image of the Month – The Rosette Nebula

About the Rosette nebula

Rosette nebula

The Rosette nebula is huge cloud of dust and ionized gas located in the direction of the constellation Monoceros.

The Rosette is over 5,000 light years away and has a diameter in the region of 130 light years. To put this into perspective the entire solar system, everything orbiting the sun right out to the most distance icy objects, has diameter less than 2 light years.

The whole area glows brightly due to the young hot stars contained within the cloud. They are pumping out many types of radiation which excites the surrounding gases which themselves then emit radiation, including at visible wavelengths. Temperatures around the stars reach 6 million degrees Kelvin.

These baby stars have been born within this cloud and you can see a number in and around the central region of the Rosette.

The cluster of young stars NGC 2244

These stars have also created the shape of the Rosette, blowing out the stars and dust from the central region, hence the darker centre.

Some of the stars responsible for this structure, apart from being young, are over 50 times the mass of our own sun and are 400,000+ times brighter.

Surrounding the darker centre, you can see darker tendril-like structures. These are made of dust and block the light coming from behind. These are all star forming regions and are known as Bok Globules.

Bok Globules in the Rosette Nebula

The star cluster in and around the centre was first discovered by astronomer John Flamsteed in 1690, but he could not see the surrounding nebulosity. This was discovered much later.

The central brighter stars can be seen with the naked eye or easily with binoculars, but seeing any nebulosity requires a modest telescope. To capture an image like the one here requires something completely different.

Imaging the Rosette

An image such as this requires many tens of hours of exposure to get the detail you can see here. In this case I imaged through a range of filters for nearly 50 hours. To build up the data I take what are called ‘sub frames’ or images of a shorter duration, which I can later stack together using astronomy software. The sub frames for the Rosette were 25 minutes each. After a night of imaging I review the results frame by frame and reject those that are not perfect. (Imperfections are typically caused by poor seeing, aircraft or satellites passing across the frame or software or hardware issues). I ended up with 35 hours of perfect sub frames for the Rosette.

I used three filters to image the Rosette, each designed to capture the emissions of certain ionized gasses. These are Sulphur II, Oxygen III and Hydrogen Alpha.

The next stage is a calibration routine which eliminates the unwanted artefacts caused by long duration exposures. Finally, I spend a long time processing the data to bring out the beauty and detail.

In this case it is one of the most beautiful images I have captured and created.

I hope you will get much pleasure from this image and the way it is presented as a piece of art. There are so many beautiful objects to enjoy in deep space!

For prices and sizes of the Rosette Nebula, click here.