Starburst galaxy sheds light on longstanding cosmic mystery

Nov 02, 2009
The Cigar Galaxy (M82) is located 12 million light years from Earth, in the direction of the Ursa Major constellation. It has an active starburst region in its center. Image courtesy of NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

( -- An international collaboration that includes scientists from the University of Delaware's Bartol Research Institute in the Department of Physics and Astronomy has discovered very-high-energy gamma rays in the Cigar Galaxy (M82), a bright galaxy filled with exploding stars 12 million light years from Earth.

The gamma rays observed by the team have energies more than a trillion times higher than the energy of visible light and are the highest-energy photons ever detected from a galaxy undergoing large amounts of star formation.

The discovery, made from data taken over a two-year-long observing campaign by the VERITAS collaboration of more than 100 scientists from 22 different institutions in the United States, Ireland, United Kingdom, and Canada, appears in the Nov. 1 advance online edition of the scientific journal Nature.

VERITAS (Very Energetic Radiation Imaging System) is a gamma ray observatory located at the Fred Lawrence Whipple Observatory near Amado, Ariz.

The finding provides "strong evidence" that exploding stars are the origin of cosmic rays, according to Jamie Holder, assistant professor of physics and astronomy at the University of Delaware and deputy spokesperson for the VERITAS collaboration.

Produced in violent processes in our own galaxy and beyond, cosmic rays are actually that continually bombard Earth's atmosphere. They are important, Holder says, because they make up a large fraction of the energy budget of our galaxy, The Milky Way. The amount of energy in cosmic rays is comparable to the energy contained in both starlight, and in Galactic magnetic fields, Holder notes.

"Although cosmic rays were first detected 100 years ago, their origins have been a mystery," says Holder. "One idea has been that they are produced by supernova explosions, but there was never any direct proof until now. This gamma ray measurement by VERITAS looks at a galaxy different from our own where there are 30 times as many supernovae. The fact that we see indicates that there are many more cosmic rays being produced by these supernovae."

This representative-color figure shows the very-high-energy gamma-ray emission observed by VERITAS coming from the Cigar Galaxy, also known as Messier 82. The black star is the location of the active starburst region. The emission from M82 is effectively point-like for VERITAS, and the white circle indicates the size of a simulated point source. The entire galaxy would be contained within the circle. Credit: CfA/V.A. Acciari

In the active starburst region at the Cigar Galaxy's center, stars are being formed at a rate approximately ten times more rapidly than in "normal" like our Milky Way, Holder says.

The produced in the formation, life, and death of the massive stars in this region eventually produce diffuse gamma-ray emission via their interactions with interstellar gas and radiation.

Holder and former postdoctoral researcher Ester Aliu and doctoral student Dana Boltuch were involved in the study from UD.

Holder scheduled all of the observations as chair of the team's observing time allocation committee, and he and Aliu ran the array of telescopes based in southern Arizona to collect a significant portion of the 137 hours of data collected for the study. Holder provided a critical secondary analysis with an independent analysis package to confirm the result.

Source: University of Delaware (news : web)

Explore further: Exomoons Could Be Abundant Sources Of Habitability

add to favorites email to friend print save as pdf

Related Stories

Very High Energy Gamma Rays

Sep 25, 2009

( -- Gamma-rays are the most energetic known form of electromagnetic radiation, with each gamma ray being at least one hundred thousand times more energetic than an optical light photon. The most ...

Galactic Center Found To Glow Unevenly

Feb 21, 2006

An international team of more than 100 astrophysicists said they have detected very-high-energy gamma rays emanating from the huge gas clouds known to pervade the center of the Milky Way galaxy.

On the Scent of a Pre-Historic Particle Accelerator?

Feb 09, 2006

An international team of astrophysicists have used the H.E.S.S. telescopes to uncover the trail of a 10,000 year old supernova at the heart of the Milky Way. In a paper published in Nature (6th February 2006), they descri ...

Recommended for you

Big black holes can block new stars

9 hours ago

Massive black holes spewing out radio-frequency-emitting particles at near-light speed can block formation of new stars in aging galaxies, a study has found.

POLARBEAR seeks cosmic answers in microwave polarization

9 hours ago

An international team of physicists has measured a subtle characteristic in the polarization of the cosmic microwave background radiation that will allow them to map the large-scale structure of the universe, ...

New radio telescope ready to probe

12 hours ago

Whirring back and forth on a turning turret, the white, 40-foot dish evokes the aura of movies such as "Golden Eye" or "Contact," but the University of Arizona team of scientists and engineers that commissioned ...

Exomoons Could Be Abundant Sources Of Habitability

Oct 20, 2014

With about 4,000 planet candidates from the Kepler Space Telescope data to analyze so far, astronomers are busy trying to figure out questions about habitability. What size planet could host life? How far ...

Partial solar eclipse over the U.S. on Thursday, Oct. 23

Oct 17, 2014

People in most of the continental United States will be in the shadow of the Moon on Thursday afternoon, Oct. 23, as a partial solar eclipse sweeps across the Earth. For people looking through sun-safe filters, from Los Angeles, ...

User comments : 0