New research by Keele University and the University of Leeds offers an explanation for the discrepancy between the size and age of the Rosette Nebula’s central cavity and that of its central stars.

The Rosette Nebula is located in the Milky Way Galaxy roughly 5,000 light-years from Earth and is known for its rose-like shape and distinctive hole at its centre. The Nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases with several massive stars found in a cluster at its heart.

Stellar winds and ionising radiation from these massive stars affect the shape of the giant molecular cloud. But the size and age of the cavity observed in the centre of Rosette Nebula is too small when compared to the age of its central stars.

Through computer simulations, astronomers at Keele University and the University of Leeds have found the formation of the Nebula is likely to be in a thin sheet-like molecular cloud rather than in a spherical or thick disc-like shape, as some photographs may suggest. A thin disc-like structure of the cloud focusing the stellar winds away from the cloud’s centre would account for the comparatively small size of the central cavity.

Keele University’s Dr Nick Wright explains:

“Using data from the new Gaia satellite we were able to measure the motion of the stars in the cluster at the heart of the nebula and found that two of the stars were moving away from each other, most likely because they had been in a binary system that had been disrupted.”

Dr Wright, who is an Ernest Rutherford Fellow supported by the Science and Technology Facilities Council, continues:

“The timescale of this disruption allowed us to place some constraints on the model that have proven to be very useful.”

Lead author of the study, Dr Christopher Wareing from the School of Physics and Astronomy at the University of Leeds, said: “The massive stars that make up the Rosette Nebula’s central cluster are a few millions of years old and halfway through their lifecycle. For the length of time their stellar winds would have been flowing, you would expect a central cavity up to ten times bigger.

“We simulated the stellar wind feedback and formation of the nebula in various molecular cloud models including a clumpy sphere, a thick filamentary disc and a thin disc, all created from the same low density initial atomic cloud.

“It was the thin disc that reproduced the physical appearance – cavity size, shape and magnetic field alignment — of the Nebula, at an age compatible with the central stars and their wind strengths.

“To have a model that so accurately reproduces the physical appearance in line with the observational data, without setting out to do this, is rather extraordinary.

Dr Wright, who is part of the Astrophysics team at Keele, also produced the image for the study:

“The image I produced is based on data and images taken from the Isaac Newton Telescope in La Palma as part of a survey of the entire Milky Way. One of the filters used in this survey detects the light coming from ionised hydrogen, the most abundant element in the Universe and the main component of bright nebulae such as the Rosette Nebula. This allowed us to map out the structure of the nebula in an unprecedented level of detail.”

The simulations, published in the Monthly Notices of the Royal Astronomical Society, were run using the Advanced Research Computing centre at Leeds. The nine simulations required roughly half a million CPU hours — the equivalent to 57 years on a standard desktop computer.

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