Astronomers pinpointed the origin of huge gas bubbles flowing from the Milky Way
(ORDO NEWS) — There is an unusual paradox that interferes with the research of some areas of the Milky Way. Dense gas bubbles block the observation of the galactic nucleus in visible light from our point of view.
To better study the Galactic Center (GC) and Interstellar Medium (ISM), a team of astronomers used a telescope called the Wisconsin H-Alpha Mapper (WHAM).
The research team focused on two features of the Milky Way, called Fermi bubbles. Fermi bubbles are massive emissions of high-energy gas coming from the galactic core.
They are called Fermi bubbles because they were discovered in 2010 by the Fermi gamma radiation space telescope. These bubbles are huge, stretching for about 50,000 light-years from the Milky Way disk, moving at a speed of millions of kilometers per hour.
The paper presenting their observations is called “Discovery of High-Speed H-Alpha Above the Galactic Center: Testing Fermi Bubble Models”. The lead author is Dhanesh Krishnarao, a graduate student in astronomy at UW Wisconsin. The results were presented at the 236th meeting of the American Astronomical Society and accepted for publication in The Astrophysical Journal Letters.
The scientists behind this study observed nitrogen emission lines in Fermi bubbles. They compared their observations with recent Hubble observations of UV light in the same position and combined them.
In a press release, lead author Krishnarao said: “We combined the two measurements of emission and absorption to estimate the density, pressure and temperature of the ionized gas, and this allows us to better understand where this gas comes from.”
In their article, the authors write, “H-Alpha Mapper (WHAM) observations show the high-speed emission lines of H alpha and [N II] λ6584 in the same direction and speed as the ultraviolet absorption lines that were previously associated with biconical gamma ray fractions, known as Fermi bubbles. ”
Astronomers believe that no matter what creates the Fermi bubbles, this happened several million years ago. Some researchers believe that Sgr A *, a supermassive black hole in the center of the galaxy, pulled a massive cloud of hydrogen into its accretion disk, causing a huge surge of energy.
In conclusion of their article, the authors describe some of their findings. They say that the results indicate a gas temperature of 8900 ± 2700 K.
But even though these conclusions are very detailed, they do not show conclusively what caused the appearance of Fermi bubbles. The team says that WHAM can provide more information. And just like in this study, future observations can also be combined with Hubble observations.
So, perhaps one day we will find out what happened several million years ago in the center of the Milky Way, which formed these giant bubbles.
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