Gamma-ray sources found in neighbouring galaxy
An international team of astronomers including IPAS Theme Leader Dr Gavin Rowell have discovered three new gamma-ray sources in our neighbouring galaxy, the Large Magellanic Cloud (LMC).
Using the High Energy Stereoscopic System (HESS) telescopes in Namibia, South-West Africa, the researchers have found three “stellar-type” or star-related sources of gamma-rays. The three sources are: the most powerful pulsar-driven nebula found to date (formed from particles flowing out from the pulsar), the most powerful supernova remnant, and a so-called “super-bubble” − a shell-shaped object that is 270 light years in diameter created by multiple massive star outflows (or winds) and supernovae explosions.
Published in the journal Science today, the HESS researchers say this is the first time that different types of gamma-ray sources have been seen from a galaxy other than the Milky Way.
“Perhaps the most exciting aspect is that it’s the first super-bubble from which we’ve definitely seen gamma-rays,” says Associate Professor Gavin Rowell, from the University’s High Energy Astrophysics Group and leader of Australia’s participation in the HESS Collaboration. “The super-bubble result provides a new observational clue that massive star outflows, or winds, may contribute to extremely high energy particle acceleration in galaxies.”
The Large Magellanic Cloud (LMC) is a dwarf satellite galaxy of the Milky Way located 170,000 light years away. It is visible to the naked eye in the southern sky during summer nights and is very active in producing new massive stars − making it a high priority target for HESS scientists in their quest to reveal the high energy secrets of galaxies.
“The detection of these gamma-rays, which have energies more than 100 billion times the energy of optical light, immediately tells us that these new sources are able to accelerate particles to extreme energies,” says Associate Professor Rowell.
“The particles could be cosmic-rays, the source of which has been puzzling astronomers for over 100 years.
“Our research findings offer further insight into the role that massive star evolution − their birth, life and death − has in accelerating such cosmic-rays.”
The HESS team consists of scientists from Germany, France, the United Kingdom, Namibia, South Africa, Ireland, Armenia, Poland, Australia, the Netherlands, Austria and Sweden.
HESS in Namibia is a system of four 13 metre diameter telescopes – recently complemented with the huge 28m HESS II telescope − and is one of the most sensitive detectors of very high-energy gamma rays.