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NAM 21: New theory of evolution for spiral galaxy arms

Last Updated on Wednesday, 20 April 2011 13:21
Published on Wednesday, 20 April 2011 13:16

grand_thumbA study of spiral patterns found in galaxies like our Milky Way could overturn the theory of how the spiral arm features form and evolve. The results are being presented by postgraduate student, Robert Grand, at the Royal Astronomical Society’s National Astronomy Meeting in Llandudno, Wales this week.

Since 1960s, the most widely accepted explanation has been that the spiral arm features move like a Mexican wave in a crowd, passing through a population of stars that then return to their original position.  Instead, computer simulations run by Grand and his colleagues at University College London’s Mullard Space Science Laboratory (MSSL) suggest that the stars actually rotate with the arms. In addition, rather than being permanent features the arms are transient, breaking up and new arms forming over a period of about 80-100 million years.

"We have found it impossible to reproduce the traditional theory, but stars move with the spiral pattern in our simulations at the same speed. We simulated the evolution of spiral arms for a galaxy with five million stars over a period of 6 billion years. We found that stars are able to migrate much more efficiently than anyone previously thought. The stars are trapped and move along the arm by their gravitational influence, but we think that eventually the arm breaks up due to the shear forces," said Grand.

In the simulations, Grand found that some stars gradually move outwards and inwards along the spiral arms. Stars travelling at the leading side of the spiral arm slide in towards the centre of the disc, whereas the stars travelling at the trailing side are kicked out to the edges.

"This research has many potential implications for future observational astronomy, like the European Space Agency's next corner stone mission, Gaia, which MSSL is also heavily involved in.  As well as helping us understand the evolution of our own galaxy, it may have applications for regions of star formation," said Grand.

 

SCIENCE CONTACTS

 

Robert Grand

Mullard Space Science Laboratory

University College London

E-mail:  This email address is being protected from spambots. You need JavaScript enabled to view it.

 

PRESS CONTACTS

 

NAM 2011 Press Office (0900 – 1730 BST, 18-21 April only)

Conwy Room

Venue Cymru conference centre

Llandudno

Tel: +44 (0)1492 873 637, +44 (0)1492 873 638

 

Dr Robert Massey

Royal Astronomical Society

Mob: +44 (0)794 124 8035

Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Anita Heward

Royal Astronomical Society

Mob: +44 (0)7756 034 243

Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

 

 

IMAGES

 

An image can be found at:

http://www.ras.org.uk/images/stories/NAM/2011/images/grand.jpg

 

Image Caption:   Snapshots of face-on view of a simulated disc galaxy. A Brighter colour indicates higher density. The Image shows two examples of star particles: the red star are travelling at the leading side of the arm, and the blue star are at the trailing side. It can be seen that the blue and red stars interchange their radial distances, with rapid migration within 40 million years. The dotted lines trace circles with radii of 4, 5 and 6 000 parsecs (1 parsec = 31 trillion kilometres), to guide the eye. 

 

NOTES FOR EDITORS

 

NAM 2011

 

Bringing together around 500 astronomers and space scientists, the RAS National Astronomy Meeting 2011 (NAM 2011: http://www.ras.org.uk/nam-2011) will take place from 17-21 April in Venue Cymru (http://www.venuecymru.co.uk), Llandudno, Wales. The conference is held in conjunction with the UK Solar Physics (UKSP: http://www.uksolphys.org) and Magnetosphere Ionosphere and Solar-Terrestrial Physics (MIST: http://www.mist.ac.uk) meetings. NAM 2011 is principally sponsored by the RAS and the Science and Technology Facilities Council (STFC: http://www.stfc.ac.uk).

 

The Royal Astronomical Society

 

The Royal Astronomical Society (RAS: http://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 organizes 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 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

 

The Science and Technology Facilities Council

 

The Science and Technology Facilities Council (STFC: http://www.stfc.ac.uk) ensures the UK retains its leading place on the world stage by delivering world-class science; accessing and hosting international facilities; developing innovative technologies; and increasing the socio-economic impact of its research through effective knowledge exchange. The Council has a broad science portfolio including Astronomy, Particle Astrophysics and Space Science. In the area of astronomy it funds the UK membership of international bodies such as the European Southern Observatory.

 

Venue Cymru

 

Venue Cymru (http://www.venuecymru.co.uk) is a purpose built conference centre and theatre with modern facilities for up to 2000 delegates. Located on the Llandudno promenade with stunning sea and mountain views; Venue Cymru comprises a stunning location, outstanding quality and exceptional value: the perfect conference package.