Astronomers discover high energy ‘super bubble’

An international team of astronomers has discovered a high energy “super bubble” lurking in a neighbouring galaxy. This is the first time a super bubble has been linked to such massively high energy and seen in a galaxy outside our own.

Scientists from the Dublin Institute for Advanced Studies were involved in the find, also helping to identify two other unusual sources of high energy in the dwarf galaxy known as the Large Magellanic Cloud. Details of the work are published in the journal Science.

These sources are giving off astounding energies of a million million electron volts, a measure of energy, said Prof Luke Drury of the Institute who with colleague Prof Felix Aharonian were participants in the work.

“This is blue skies stuff literally,” said Prof Drury who heads the Institute’s school of cosmic physics. Finding these sources could help us better understand the mystery surrounding cosmic rays.

"It was very significant to find a super bubble. This is the first time one was confirmed as a gamma ray source, " he said.

“These results are very exciting, but the biggest surprise, of course, is the detection of the super bubble,” Prof Aharonian said.

The super bubble in question is a shell measuring 270 light years across and formed by being blown up like a balloon by exploding stars going supernova. It is pumping out incredibly strong gamma rays.

So too are the two other objects, a pulsar - a fast spinning collapsed star- and the remains of another supernova, one of the oldest known and glowing like a beacon in powerful gamma rays.

Scientists are interested in these high energy sources because of their links with cosmic rays, said Prof Drury. Cosmic rays are immensely high energy radiation coming from somewhere well outside our solar system. Something creates them and sends them off with huge energies.

They are not directly detected, their path is seen when they slam into our upper atmosphere and kick off cascades of illumination called Cherenkov light.

Profs Drury and Aharonian, who is at the Institute and also heads the high energy astrophysics theory group at the Max Planck Institute in Germany, are participants in a consortium of about 20 countries using an advanced telescope based in Namibia called the High Energy Stereoscopic System, Hess.

It had to “stare” for 210 hours at a small part of the Large Magellanic Cloud to dig out these three gamma ray sources.