"What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center," said Doug Finkbeiner, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who first recognized the feature. "We don't fully understand their nature or origin."
At more than 100 degrees across, the structure spans more than half of the sky, from the constellation Virgo to the constellation Grus. It may be millions of years old.
A paper on the findings will appear in an upcoming issue of The Astrophysical Journal.
Finkbeiner and Harvard graduate students Meng Su and Tracy Slatyer revealed the bubbles by processing publicly available data from the satellite's Large Area Telescope (LAT). Their work expanded on previous studies led by Greg Dobler at the Kavli Institute for Theoretical Physics in Santa Barbara, Calif.
Fermi's Large Area Telescope is the most sensitive and highest-resolution gamma-ray detector ever orbited. Gamma rays are the highest-energy form of light.
The structures eluded previous astronomers studying gamma rays due in part to the so-called diffuse emission -- a fog of gamma rays that appears all over the sky. The emissions are caused by particles moving near the speed of light interacting with light and interstellar gas in the Milky Way.
The Fermi LAT team is constantly refining models to uncover new gamma-ray sources obscured by the diffuse emission. By using various estimates of the gamma-ray fog, including the Fermi team's, Finkbeiner and his colleagues were able to subtract it from the LAT data and unveil the giant bubbles.
"The LAT team confirmed the existence of an extended structure in the direction of the inner part of the Milky Way and we're in the process of performing a deeper analysis to better understand it," said Simona Murgia, a Fermi research associate at the SLAC National Accelerator Laboratory in Menlo Park, Calif.
The researchers believe that an important process for producing the Milky Way's gamma-ray fog, called inverse Compton scattering, also lights up the bubbles. In that process, electrons moving near the speed of light collide with low-energy light, such as radio or infrared photons. The collision increases the energy of the photons into the gamma-ray part of the electromagnetic spectrum.
The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way.
The bubbles also appear to have well-defined edges. Taken together, the structure's shape and emissions suggest that it was formed as a result of a large and relatively rapid energy release -- the source of which remains a mystery, Finkbeiner noted.
One possibility includes a particle jet from the supermassive black hole at the galactic center. In many other galaxies, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence that the Milky Way's black hole sports such a jet today, it may have in the past.
The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way's central light-years several million years ago.
"In other galaxies, we see that starbursts can drive enormous gas outflows," said David Spergel at Princeton University in New Jersey. "Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics."
Finkbeiner noted that, in retrospect, hints of the bubbles appear in earlier spacecraft data, including the Germany-led Roentgen X-ray Satellite (ROSAT) and NASA's Wilkinson Microwave Anisotropy Probe (WMAP).
This release is being issued jointly with NASA.
NASA's Fermi Gamma Ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States. Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.
For more information, contact:David A. Aguilar
Christine Pulliam | EurekAlert!
Unraveling the nature of 'whistlers' from space in the lab
15.08.2018 | American Institute of Physics
Early opaque universe linked to galaxy scarcity
15.08.2018 | University of California - Riverside
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur
What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...
08.08.2018 | Event News
27.07.2018 | Event News
25.07.2018 | Event News
15.08.2018 | Physics and Astronomy
15.08.2018 | Earth Sciences
15.08.2018 | Physics and Astronomy