London: A team of astronomers has taken the most sensitive image of a galaxy 30 million light years away via a radio telescope with frequencies just above those of commercial FM radio stations.
The European astronomers took images of `Whirlpool Galaxy` Messier 51 (M51) with the Low Frequency Array (LOFAR) radio telescope in the frequency range 115-175 MHz that is just above the normal commercial FM radio frequency band of 88-108 MHz.
Radio astronomy has not been able to explore low frequencies below 300 MHz because the ionosphere around the Earth acts as a barrier of low-frequency radio waves.
The only observations were of poor resolution and no details could be made out.
"Low-frequency radio waves are important as they carry information about electrons of relatively low energies that are able to propagate further away from their places of origin in the star-forming spiral arms and are able to illuminate the magnetic fields in the outer parts of galaxies," said David Mulcahy from the University of Southampton`s astronomy group.
The signals from all stations of LOFAR spreading across the Netherlands, Germany, Britain, France and Sweden were combined in a powerful computing cluster located at University of Groningen in the Netherlands.
With LOFAR`s high sensitivity, the astronomers detected electrons and magnetic fields in the spiral arms and extended disc of M51, 40,000 light years away from the galaxy`s centre - much further out than had ever been traced before.
Radio astronomy shows two crucial components of galaxies that are invisible to optical telescopes - cosmic ray electrons and magnetic fields - which play an important role in the stability and evolution of galaxies.
The research is published in the journal Astronomy & Astrophysics.