Space
Hot Gas Around Milky Way May Have Answers to Missing Baryons
Brooke Miller
First Posted: Sep 25, 2012 06:16 AM EDT
Astronomers have found evidence that our Milky Way Galaxy is surrounded in an enormous halo of hot gas that extends for hundreds of thousands of light years. This observation was made by NASA's Chandra X-ray Observatory. The approximate mass of the halo is similar to the mass of all the stars in the galaxy.
If the astronomers get a confirmation on the size and mass of the gas halo, then it stands as a strong explanation for the "missing baryon" problem for the galaxy. Baryons that consist of neutron and protons make up 99 percent of the mass of the atoms in the cosmos. Based on the measurements of extremely distant gas halos and galaxies indicate that the baryonic matter existed when universe was just a few billion years old and consisted of up to one sixth of the dark matter.
Based on the data from Chandra, the European Space Agency's XMM Newton space observatory and Japan's Suzaku satellite, they set limits on the temperature, extent and mass of the hot gas halo. Nearly eight bright X-ray sources were located by Chandra that placed beyond the galaxy at distances of hundreds of millions of light-years. The scientists estimate that the temperature of the absorbing halo is between 1 million and 2.5 million kelvins, or a few hundred times hotter than the surface of the sun.
Prior to this studies have been done that highlighted the presence of hotter gas with a temperature greater than 1 million Kelvin's. But this research shows evidence that the hot gas halo envelops the Milky Way is much more massive than the warm gas halo.
"We know the gas is around the galaxy, and we know how hot it is," said Anjali Gupta, lead author of The Astrophysical Journal paper describing the research. "The big question is, how large is the halo, and how massive is it?"
For this the researchers supplemented Chandra data on the amount of absorption produced by the oxygen ions with XMM-Newton and Suzaku data on the X-rays emitted by the gas halo. They summed up stating the mass of the gas is equivalent to the mass in more than 10 billion suns, perhaps as large as 60 billion suns.
"Our work shows that, for reasonable values of parameters and with reasonable assumptions, the Chandra observations imply a huge reservoir of hot gas around the Milky Way," said co-author Smita Mathur of Ohio State University in Columbus. "It may extend for a few hundred thousand light-years around the Milky Way or it may extend farther into the surrounding local group of galaxies. Either way, its mass appears to be very large."
The estimation made represents an important step in solving the case of the missing baryons, a mystery that has puzzled astronomers for more than a decade.
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First Posted: Sep 25, 2012 06:16 AM EDT
Astronomers have found evidence that our Milky Way Galaxy is surrounded in an enormous halo of hot gas that extends for hundreds of thousands of light years. This observation was made by NASA's Chandra X-ray Observatory. The approximate mass of the halo is similar to the mass of all the stars in the galaxy.
If the astronomers get a confirmation on the size and mass of the gas halo, then it stands as a strong explanation for the "missing baryon" problem for the galaxy. Baryons that consist of neutron and protons make up 99 percent of the mass of the atoms in the cosmos. Based on the measurements of extremely distant gas halos and galaxies indicate that the baryonic matter existed when universe was just a few billion years old and consisted of up to one sixth of the dark matter.
Based on the data from Chandra, the European Space Agency's XMM Newton space observatory and Japan's Suzaku satellite, they set limits on the temperature, extent and mass of the hot gas halo. Nearly eight bright X-ray sources were located by Chandra that placed beyond the galaxy at distances of hundreds of millions of light-years. The scientists estimate that the temperature of the absorbing halo is between 1 million and 2.5 million kelvins, or a few hundred times hotter than the surface of the sun.
Prior to this studies have been done that highlighted the presence of hotter gas with a temperature greater than 1 million Kelvin's. But this research shows evidence that the hot gas halo envelops the Milky Way is much more massive than the warm gas halo.
"We know the gas is around the galaxy, and we know how hot it is," said Anjali Gupta, lead author of The Astrophysical Journal paper describing the research. "The big question is, how large is the halo, and how massive is it?"
For this the researchers supplemented Chandra data on the amount of absorption produced by the oxygen ions with XMM-Newton and Suzaku data on the X-rays emitted by the gas halo. They summed up stating the mass of the gas is equivalent to the mass in more than 10 billion suns, perhaps as large as 60 billion suns.
"Our work shows that, for reasonable values of parameters and with reasonable assumptions, the Chandra observations imply a huge reservoir of hot gas around the Milky Way," said co-author Smita Mathur of Ohio State University in Columbus. "It may extend for a few hundred thousand light-years around the Milky Way or it may extend farther into the surrounding local group of galaxies. Either way, its mass appears to be very large."
The estimation made represents an important step in solving the case of the missing baryons, a mystery that has puzzled astronomers for more than a decade.
See Now: NASA's Juno Spacecraft's Rendezvous With Jupiter's Mammoth Cyclone