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Astrophysicists map out the light energy contained within the Milky Way

Last Updated on Friday, 28 July 2017 09:17
Published on Friday, 28 July 2017 05:00

For the first time, a team of scientists have calculated the distribution of all light energy contained within the Milky Way, which will provide new insight into the make-up of our galaxy and how stars in spiral galaxies such as ours form. The study is published in the journal Monthly Notices of the Royal Astronomical Society.

 

This research, conducted by astrophysicists at the University of Central Lancashire (UCLan), in collaboration with colleagues from the Max Planck Institute for Nuclear Physics in Heidelberg, Germany and from the Astronomical Institute of the Romanian Academy, also shows how the stellar photons, or stellar light, within the Milky Way control the production of the highest energy photons in the Universe, the gamma-rays. This was made possible using a novel method involving computer calculations that track the destiny of all photons in the galaxy, including the photons that are emitted by interstellar dust, as heat radiation.

 

thumb MW all skyAn all-sky image of the Milky Way, as observed by the Planck Space Observatory in infrared. The data contained in this image were used in this research and were essential in calculating the distribution of the light energy of our Galaxy. Credit: ESA / HFI / LFI consortia. Click for a larger imagePrevious attempts to derive the distribution of all light in the Milky Way based on star counts have failed to account for the all-sky images of the Milky Way, including recent images provided by the European Space Agency's Planck Space Observatory, which map out heat radiation or infrared light.

 

Lead author Prof Cristina Popescu from the University of Central Lancashire, said: "We have not only determined the distribution of light energy in the Milky Way, but also made predictions for the stellar and interstellar dust content of the Milky Way.”

 

By tracking all stellar photons and making predictions for how the Milky Way should appear in ultraviolet, visual and heat radiation, scientists have been able to calculate a complete picture of how stellar light is distributed throughout our Galaxy. An understanding of these processes is a crucial step towards gaining a complete picture of our Galaxy and its history.

 

The modelling of the distribution of light in the Milky Way follows on from previous research that Prof Popescu and Dr Richard Tuffs from the Max Planck Institute for Nuclear Physics conducted on modelling the stellar light from other galaxies, where the observer has an outside view.

 

Commenting on the research, Dr Tuffs, one of the co-authors of the paper, said: “It has to be noted that looking at galaxies from outside is a much easier task than looking from inside, as in the case of our Galaxy.”

 

Scientists have also been able to show how the stellar light within our Galaxy affects the production of gamma-ray photons through interactions with cosmic rays. Cosmic rays are high-energy electrons and protons that control star and planet formation and the processes governing galactic evolution. They promote chemical reactions in interstellar space, leading to the formation of complex and ultimately life-critical molecules.

 

Dr Tuffs added: "Working backwards through the chain of interactions and propagations, one can work out the original source of the cosmic rays."

 

The research, funded by the Leverhulme Trust, was strongly interdisciplinary, bringing together optical and infrared astrophysics and astro-particle physics. Prof Popescu notes: “We had developed some of our computational programs before this research started, in the context of modelling spiral galaxies, and we need to thank the UK's Science and Technology Facility Council (STFC) for their support in the development of these codes. This research would also not have been possible without the support of the Leverhulme Trust, which is greatly acknowledged.”

 

Media contacts

 

Sophie Roberts

thisismc2 (on behalf of UCLan)

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Dr Morgan Hollis

Royal Astronomical Society

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Dr Robert Massey

Royal Astronomical Society

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Science contacts

 

Prof Cristina Popescu

Jeremiah Horrocks Institute

University of Central Lancashire

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Dr Richard Tuffs
Max Planck Institute for Nuclear Physics
Tel: +49 6221 516 344
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Images and captions

 

An all-sky image of the Milky Way, as observed by the Planck Space Observatory in infrared. The data contained in this image were used in this research and were essential in calculating the distribution of the light energy of our Galaxy. Credit: ESA / HFI / LFI consortia.

 

Further information

 

The new work appears in: "A radiation transfer model for the Milky Way: I. Radiation fields and application to high-energy astrophysics", C.C. Popescu, R. Yang, R.J. Tuffs, G. Natale, M. Rushton, F. Aharonian, Monthly Notices of the Royal Astronomical Society (2017) 470 (3): 2539-2558 (DOI: 10.1093/mnras/stx1282).

A copy of the paper is available from: http://adsabs.harvard.edu/abs/2017MNRAS.470.2539P

 

Cristina Popescu acknowledges support from the Leverhulme Trust Research Project Grant RPG-2013-418. The Leverhulme Trust was established by the Will of William Hesketh Lever, the founder of Lever Brothers. Since 1925 the Trust has provided grants and scholarships for research and education. Today, it is one of the largest all-subject providers of research funding in the UK, distributing approximately £80m a year. For more information about the Trust, please visit www.leverhulme.ac.uk. Cristina Popescu also acknowledges support from the UK Science and Technology Facility Council (STFC; grant ST/J001341/1).

 

Notes for editors

 

The Royal Astronomical Society (RAS, www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organises scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

T: https://twitter.com/royalastrosoc

F: https://facebook.com/royalastrosoc

 

The University of Central Lancashire (UCLan) in Preston was founded in 1828 as the Institution for the Diffusion of Knowledge. Since those early days it has grown into one of the UK’s largest universities with a staff and student community approaching 38,000 and an employment-focused course portfolio containing over 350 undergraduate programmes and nearly 250 postgraduate courses. The University has an established research reputation with world-leading or internationally excellent work taking place within the areas of Business, Health, Humanities and Science.

As a truly global institution with an established campus in Cyprus, UCLan’s student body includes 120 nationalities and its partnership network extends to 125 countries. In 2013 the Quacquarelli Symonds World University Rankings awarded UCLan the full five stars for its global outlook in all aspects of international educational provision. In 2016 the Centre for World University Rankings placed UCLan in the top 3.7 percent of all worldwide universities.

The University has a strong focus on continually improving the student experience and recently unveiled a 10-year, £200 million plan to redevelop its Preston Campus to create an attractive and inviting, world-class campus helping to create jobs, kick-start regeneration and attract inward investment into the City.