The Low Frequency Array (LOFAR) radio telescope has been used to observe the glowing center of the starburst galaxy Messier 82 at very long radio wavelengths.
The center of the galaxy Messier 82 at very long radio wavelengths; the bright points are most likely supernova remnants; the image is about 3,300 light years across. Image credit: E. Varenius / Onsala Space Observatory / LOFAR Collaboration.
Messier 82, also known as NGC 3034 or the Cigar Galaxy, is an irregular galaxy located in the northern constellation Ursa Major, about 12 million light-years away.
The galaxy, which is approximately 40,000 light-years across, is creating stars at 10 times the rate of normal galaxies.
The reason for this is the relatively recent encounter with its close neighbor Messier 81. The latest encounter is thought to have occurred around a hundred million years ago, during which Messier 82 was significantly disrupted.
Messier 82 is a favorite object for many astronomers who investigate the evolution of stars and galaxies.
In images taken in visible light, the galaxy is a riot of stars, gas and dust. LOFAR shows astronomers a completely different scene.
“In LOFAR’s new extremely sharp image we are seeing a collection of bright spots, which are most likely supernova remnants,” said Dr Eskil Varenius from Chalmers University of Technology in Onsala, Sweden, the first author of a paper published in the journal Astronomy & Astrophysics (arXiv.org preprint).
“This galaxy is millions of light-years away, and each remnant can be as little as a few light-years across. We need extremely sharp images to study them.”
The supernova remnants are embedded inside a huge, diffuse cloud of charged particles, or plasma, which absorbs radio waves from these sources.
By investigating how different wavelengths pass through the plasma, scientists can learn more about how a gigantic star factory like Messier 82 works.
“We’re surprised that LOFAR can see as many as 16 bright supernova remnants in Messier 82,” said co-author Dr John Conway of Chalmers University of Technology.
“This image can give us new clues to the structure of Messier 82 and why so many stars are being formed there.”
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E. Varenius et al. Subarcsecond international LOFAR radio images of the M82 nucleus at 118 MHz and 154 MHz. A&A, published online November 11, 2014; doi: 10.1051/0004-6361/201425089
